Wednesday, February 29, 2012

Foggy Mornings, Warm Afternoons

By Jay Grymes & Steve Caparotta

A quasi-stationary front to our north -- draped from northern Mississippi into northern Louisiana and west into east Texas -- will begin backing northward as a warm front by tomorrow.  This means that WAFB communities remain in the “warm sector,” the region south of the warm front and east of the cold front and dominated by a mild and moist Gulf air mass.  Simple translation: dewpoints and humidity remain high, so plan on more morning fog and more afternoon 80°s for Thursday and Friday.

With fog redeveloping later tonight, the NWS has already issued a DENSE FOG ADVISORY for late tonight into Thursday morning.  The humid air, with dewpoints in the 60°s to near 70°, will mean another muggy start to the day for Thursday under the clouds.  We think that the Gulf air mass will become slightly unstable by Thursday afternoon, so given the mid-day warm-up into the 80°s, we’ll put rain chances for Thursday (mainly the afternoon and early evening) at 20%.

Continued warmth and the unstable air mass, along with an advancing front out of Texas, will mean somewhat better rain chances for Friday afternoon and early evening -- for now, we’ll go with 30% rain chances during that time window.  Rain chances will increase to about 60% or more by late Friday night into the early morning hours of Saturday as that Texas cool front moves across the Bayou State.

Titan9 RPM model projection for 7 a.m. Saturday showing a cool front bringing rains to the area.
We still believe that Saturday’s front will be a fast-mover, with the boundary moving south and east and  over the Gulf by Saturday afternoon and evening.  However, some of the models are suggesting that clouds and possibly even a few light showers could linger well into the day on Saturday.  Our thinking is that the rains are out of the BR metro area by mid-morning, with clearing underway by the mid-afternoon. 

Saturday’s front will deliver cooler, but not cold, air -- highs on Saturday will run in the 60°s.  Sunday, Monday and Tuesday all look like nice weather days, with a chance of rain returning for next Wednesday.

It should come as no surprise that our “calendar winter” (Dec-Jan-Feb) has proven to be rather warm this past season.  Earlier today, Jeff and Diane noted that Baton Rouge has seen only about half the normal number of freezes thus far, and records show no hard freezes (26° or below) yet this winter either.  As we turn the corner into March, historical statistics tell us that the chance of a hard freeze for Baton Rouge is almost nil, but that there remains better than a 1-in-3 chance for at least one more freeze.  In fact, the latest spring freeze ever for the Red Stick occurred on April 13 (back in 1940).

But … there is another factor to consider:  the general circulation pattern throughout most of the winter has been one that has persistently bottled-up cold air well to our north and directed Arctic outbreaks off to our east, keeping the central Gulf Coast on the mild side.  And projections for the coming weeks show a high likelihood for temperatures to continue to trend above-normal.

So -- could we get another light freeze in the next couple of weeks? 

Well, yes -- almost anything is possible in the world of weather.  But assuming that this basic upper-air circulation pattern of past weeks remains essentially intact, the chances for another freeze event seem well below the historical “1-in-3” probability.

So how about the winter as a whole?  The 2011-12 winter will rank as the 9th ‘warmest’ since at least 1930.  But maybe even more interesting is the fact that Baton Rouge records show our recent winter ranks as the ‘warmest’ since all the way back to 1971-72 – 40 winters ago!  (And for the true trivia buffs, a look at the records shows that the winters of the 1930s and 1940s account for five of the top ten ‘warmest’ winters for the Red Stick.)

Tuesday, February 28, 2012

More Fog, More Warmth

By Jay Grymes & Steve Caparotta

Highs climbed into the upper 70°s with some 80°s for highs today, as the 2011-2012 winter continues on its run of warmer-than-normal days. Have you noticed the sizes of the mosquitoes lately? Yikes!

The warm weather remains in place through the rest of the work week. You’ll notice the humid, Gulf air as well, making for sultry days by late February and early March standards. Not only will highs be running around 80° for the next three days, but morning lows will also be well-above normal, running in the 60°s for many WAFB neighborhoods! The current weather pattern will mean more mornings with areas of dense fog and afternoons where you’ll be cranking up the air-conditioners. For now, the National Weather Service in Slidell has decided not to post a Dense Fog Advisory for most of our viewing area, but you can see advisories have been posted both to our east and west.

Although most of us stay dry, we can’t rule out a sprinkle or two on Wednesday and we’ll put a 20% chance of mainly-afternoon showers in the Thursday forecast.

A big change in our weather comes during the latter half of Friday into early Saturday as a fast-moving cold front pushes into and through the state. The front looks a little slower today than forecast guidance showed yesterday, so we’ve lowered Friday rain chances and upped the rain chances for Saturday morning. For now, this looks to be a late night to early morning event for most of us. It is still a little too early to tell at this point, but we can’t rule out a strong storm or two with the frontal passage.

Titan9 RPM model projection for Noon on Friday. The cool front seen to our west will likely deliver our best rain chances early on Saturday.

But as a “fast mover,” we should see improving conditions during the mid-day and afternoon on Saturday, with noticeably cooler air as well. Set Saturday afternoon’s high in the mid to upper 60°s, with a fine-looking Sunday under mostly sunny skies and highs in the upper 60°s.

Into the extended, the early part of next week looks good as well, with dry days and highs around 70° for Monday and Tuesday.

Monday, February 27, 2012

Morning Fog, Warmer Next Couple of Days

By Jay Grymes & Steve Caparotta

With the thick clouds hanging on throughout the day, it didn’t get as warm as expected. In fact, some WAFB neighborhoods never made it into the 60°s, and the high at Metro Airport was a cool 61°F!

Visible satellite image from 4 p.m. showing low clouds covering most of the area.

Scattered showers -- in many cases, brief sprinkles at best -- dotted the WAFB area, but few locations received enough rain to even measure in the raingage! A couple of places in Terrebonne and Lafourche parishes may have seen as much as one-half-inch of rain today, but today's main rain and storm action was limited to the coastal margin and over the coastal waters.

Plenty of low-level moisture and relatively light winds will lead to the threat of locally dense fog over the next couple of mornings. In fact, fog has lingered just north of a warm front along the coast much of the day, with somewhat reduced visibilities even being reported farther inland.

We’ll keep a decent cloud deck in place through the night and set rain chances at around 20% for the overnight and early morning forecast. We’ll also maintain rain chances at 20% through the day on Tuesday under mostly cloudy skies. The biggest difference between Monday and Tuesday will be the afternoon temperatures as highs are expected to reach the upper 70°s for Tuesday afternoon!

As it often does, the work week forecast has needed some tweaking already. What looked like a “wet” week is now looking a bit drier, although certainly not rain-free.

We’ll remain in the nation’s “warm sector” in terms of the large-scale weather pattern over the next couple of days, with rain chances running in the 20% to 30% range for Tuesday, Wednesday and Thursday ... at the same time, highs for those three days will be running in the upper 70°s to around 80°!

An advancing cool front will work its way into NW Louisiana by Wednesday, but early indications are that it will stall and wash-out as it tries to cut across the Bayou State from Wednesday into Thursday.

Titan9 RPM model projection for 7 p.m. Wednesday. A cool front will likely stall just to our north, leading to small rain chances Wednesday and Thursday.

Our viewing area's next frontal passage is currently scheduled for a late Friday arrival. This system looks like it will be a “very fast mover,” entering the state from the northwest during the latter half of Friday and pushing out into the Gulf by or before dawn on Saturday. Still we’re giving this system a decent chance for producing rain in our region, with a few t-storms possible, during a 12-18 hour window.

But that should leave us with a decent Saturday afternoon and a good-looking Sunday!

Friday, February 24, 2012

Staying Cool This Weekend

By Jay Grymes & Steve Caparotta
As expected, the front slipped through during the early morning hours, wetting a few streets for the morning drive and prompting a quick drop in both air and dewpoint temperatures as it moved through.  Friday’s high temp of 73° occurred around 2AM, with temps dropping from 70° at 7AM to 63° at 8AM.  And the dewpoint temperature -- a measure of moisture in the air -- has plummeted from the upper 60°s ahead of the front (rather humid for February) down to the upper 20°s this afternoon.
As of 4PM, Titan9 Doppler radar is still showing a broken band of light rain across southeast Louisiana, with that band slowly moving to the east and SE.  Some of those radar returns are probably not reaching the ground given the very dry (low dewpoint) characteristics near the surface.
Mostly cloudy skies this evening will show slow, steady improvement overnight, with fair skies expected by Saturday’s sun-up.  The clearing skies, “dry” air and light north-to-NE flow will mean a chilly start to the day -- look for sunrise lows in the upper 30°s for many neighborhoods along and north of the I-10/12 corridor.
Clouds will be returning to the area through the day on Saturday, as a mid/upper-level disturbance along the southern Texas coast tracks to the east and ENE across the Gulf.   High and mid-level clouds will be the main impact from this feature, but we can’t rule out spotty showers for Saturday afternoon and evening, especially for the coastal parishes.
In fact, we’ll keep a 20% rain chance in the forecast for early Sunday.  As the core of the disturbance continues to the east through the day, we should see some improvement into Sunday afternoon.  But the Canadian air mass that is moving into our area this evening stays pretty much in control of our weekend temperatures, with highs in the low 60°s for both days.
We’ll begin a warm-up on Monday, with 70°s for highs on the board for much of the upcoming work week.  And we’ll also work rain chances back into the forecast for Tuesday through next Friday.
Here’s a little food for thought:
After a dry start to the winter, many of us have experienced a “wet” run recently.  As you may recall, we’ve talked at length about the recent persistence of La Niña conditions and how La Niñas serve as a good forecasting tool in anticipation of dry weather for this time of year.  In fact, since the 1950s, roughly 75% to 80% of past La Niñas were associated with dry winter/springs across south Louisiana. 
Many of you have seen more than enough rain in recent weeks, and we’ve even seen a few rivergage sites go into flood.  Yet the reality is that the majority of communities in the WAFB region are still reporting below-normal rainfall for the period of November 1 through today.  Closer to the coast, a number of sites are well-below normal for the 4-month period, with a few locations reporting less than half their normal rainfall for the period.

Thursday, February 23, 2012

Windy Today, Cooler Friday

By Jay Grymes & Steve Caparotta

Southwesterly winds were the lead topic in today’s weather story, sustained in the 20-30 mph range throughout the afternoon with gusts into the 30s!  And the air had a springtime feel to it, with Gulf humidity combining with highs in the upper 70°s to low 80°s, making it feel more like late April than late February.

Thursday's peak wind gusts (in mph) through 4 p.m.

All of this is occurring as a result of a steep pressure gradient over the state as a cool front approaches from the northwest.  We’re expecting the front to be moving into and through metro Baton Rouge during Friday morning around 6AM or so and continue moving to the SE and over the coastal waters by the middle to late afternoon.  We’ll set rain chances for Baton Rouge at 40% to 50% for the morning hours on Friday -- some neighborhoods will see little if any rain, with most neighborhoods, if not all, getting well under one-quarter-inch of rain for the event.

Titan9 RPM model projection for 6 a.m. Friday

Yes, this is the same front that had us on the watch for a potential severe-weather outbreak -- but the latest rounds of computer guidance take that threat off the weather boards!  While a few may hear a rumble or two of thunder on Friday morning, and a handful may see a some flashes of lightning, this is not going to be the strong, stormy front that was suggested by the NWS Storm Prediction Center.  The stormy weather associated with this system will remain far to our north, with our only concern locally being slick streets during the morning commute.

The other notable aspect for Friday’s weather will be the “upside-down” temperature pattern we anticipate.  Temps around midnight tonight will still be around 70° for many WAFB communities, easing down into the 60°s as the front pushes through in the morning.  Rather than rising to a daytime high during the afternoon, we expect Friday’s temperatures to display a slow but near-steady fall throughout the daylight hours, with late afternoon readings in the 50°s for many of us.

Titan9 RPM model forecast temps for 3 p.m. on Friday. Friday's anticipated high temps in the lower 70°s will likely occur near midnight, with readings falling into the 50°s for much of the day.

We’re going to keep an eye on a weak, mid-level disturbance over the western Gulf during the weekend.  Yesterday, the models were hinting that this Gulf system might become sufficiently organized to produce a little rain for us.  But the latest computer runs are less impressive with this “Gulf mess,” keeping the core of it well south of the Louisiana coast.  Even so, it may generate some mid/upper clouds and could potentially kick-off a sprinkle or two along the coast.

Titan9 RPM model projection for 3 p.m. Saturday showing the potential for a few showers along the coast.

Given that, let’s plan on fair to partly cloudy skies for Saturday, with wake-up temps in the upper 30°s for many along and north of the I-10/12 corridor.  Afternoon highs will top-out in the low 60°s, with some WAFB communities to the north and east of metro BR not getting out of the 50°s.  We’ll give it a 20% chance of rain on Sunday, with a morning low in the low 40°s and highs in the low 60°s.

Our forecast stays “unsettled” for Monday and Tuesday, with our next cool front arriving Wednesday.

Wednesday, February 22, 2012

Record Highs Possible Thursday

By Jay Grymes & Steve Caparotta

We opened Ash Wednesday with a Dense Fog Advisory thanks to light winds and a moist air mass in place over the WAFB viewing area.  And it was “clouds a-plenty!” throughout the day with a few neighborhoods even getting a mid-morning sprinkle!
It looks like the clouds will stay with us tonight and into Thursday as well.  We also expect fog to re-develop later tonight, although we anticipate that tonight’s and tomorrow morning’s moderate winds (SW, 5-10 mph) should limit the extent of significant morning fog to wind-sheltered areas.

Our forecast for Thursday calls for a high of 82° at Metro Airport -- that would tie the record for February 23rd, a record standing since 1909!  If we get some significant breaks in the mid-day clouds, we could see a few Weather Watchers reach the mid 80°s.  But the warmth won’t be Thursday’s only weather story: look for sustained winds occasionally running in the ‘teens and 20s during Thursday afternoon, with gusts occasionally in the upper 20s to above 30 mph!  Those winds will also help keep many of us from reaching the mid 80°s.

Normal, forecast and record temps for Thursday in Baton Rouge.

The cool front we’ve been talking about for the past few days is still scheduled to arrive in the WAFB viewing area early Friday, but the models and guidance still are sending mixed signals.  The NWS Storm Prediction Center is maintaining a “SLIGHT RISK” for severe weather for our area from mid-to-late Thursday into Friday morning.  But we think that the ingredients for a stormy overnight and early morning seem to be on the wane based on a couple (but not all!) forecast computer models. 

As an example, Our in-house Titan9 model is barely even showing Friday’s front as much of a rain-maker!  We think our model is underplaying the frontal passage, but it is just one of the models that seems to be suggesting a “pass” on the severe weather threat.  While the air mass ahead of the advancing cool front will be moist and unstable, there may not be sufficient lift and upper-level support to generate a widespread storm event for our region. For now, we’ll keep rain chances at about 50% for the late Thursday/early Friday time frame and we’ll keep tabs on the models for any changes in Friday’s developing weather story.  We can’t rule out a few strong t-storms as yet, but the greater weather threat looks to be well to our north. 

What about the weekend?  You will definitely notice the cool-down after Friday’s front pushes through.  Look for lows near 40° for metro BR on both Saturday and Sunday morning.  Saturday should be a mainly-fair day, but a tad on the breezy-and-cool side with afternoon highs in the low 60°s.  Sunday afternoon will only be a couple of degrees warmer, and we’ll add in a very slight chance (at 20% or less) of afternoon showers.

The forecast for Monday through Wednesday of next week calls for a return to warmer weather, but is also looks rather unsettled, with scattered rains post for each day.

Tuesday, February 21, 2012

Feeling Like Spring!

By Jay Grymes & Steve Caparotta

Happy Mardi Gras!  Mother Nature certainly did her job as the day was just about perfect for area parades!

Florida Parish Rivers Update: The Amite River at Denham Springs has begun a slow fall and should be back below flood stage (29.0 ft) later this evening.  The Amite at Bayou Manchac Point still has another couple of inches to go before cresting somewhere close to 10.5 ft later tonight or early Wednesday -- that gage should be back below flood stage by Wednesday evening.  Farther down the Amite, neither Port Vincent nor French Settlement will reach flood stage, but a number of local roads and cul-de-sacs have standing water.  Elsewhere, only the Tangipahoa at Robert remains above flood stage at about 17.5 ft (as of Tuesday afternoon).  Robert has begun a slow, steady fall today, and should drop below flood stage by early Thursday.

We’re dropping the chances for rain out of the Wednesday forecast, leaving just a spotty shower or two for the afternoon.  Likewise, we’re posting only spotty showers (less than a 20% chance) in the Thursday afternoon forecast.  Great news for those young’uns that have the better part of the week off from school!  Wednesday’s high will climb into the upper 70°s for metro Baton Rouge with highs approaching 80° for Thursday.  Both days will be partly-to-mostly cloudy -- not the prettiest of days but certainly not bad for getting outdoors during February!

A Pacific front rolls into Louisiana early Friday, giving us a decent chance of rain, especially during the first half of the day.  Admittedly, we’re getting some mixed signals from our computer guidance regarding Friday’s rain chances, with our in-house Titan9 model looking rather dry through the day on Friday.  We’re going to go with a 40% to 50% chance of rain for the time being.  For now, this frontal system looks like it will be a “quick-mover” and will race out into the central and southern Gulf by early Saturday.  The cooler air behind Friday’s front will keep highs in the 60°s for Friday and Saturday.

The uncertainty in Friday's forecast stems from how the computer models handle an upper-low currently near Baja California. Some of the guidance keeps the low meandering well to our west on Friday, while other projections have the system moving along the Gulf Coast, implying a more active scenario.

The GFS model keeps an upper-low over northern Mexico on Friday, resulting in little severe weather threat along the Gulf Coast. The ECMWF ('European') model tracks the system right along the Gulf Coast Friday, implying a significant severe weather threat.
We'll continue to monitor model trends, but if we were to lean in a certain direction, it would probably be toward the European model which has shown a bit more consistency the last couple of days. The Storm Prediction Center is leaning that way as well, putting us under a slight risk of severe weather early on Friday.

Current NWS rainfall projections suggest that we could see upwards of 1” of rain from Friday’s frontal passage.  That seems like it may be a tad high given some of the forecast uncertainty, and certainly that would not be great news for folks living along our local rivers.  But the good news is that regardless of Friday’s forecast, all of the gaging sites along the Florida Parish rivers (the Amite, Tangipahoa and others) will be well-below flood stage before rains arrive.  If we can keep Friday’s storm totals around 1” (or less), there shouldn’t be any real concerns.

NOAA/HPC rain projection from 6 p.m. Thursday through 6 p.m. Friday

For now, we’re going with a mainly dry weekend ahead: fair skies on Saturday and partly-cloudy skies with spotty afternoon showers for Sunday.  One of our guidance models is hinting at the potential development of an upper-level disturbance that slides across the northern Gulf -- if that were to occur, we would expect clouds over the weekend and our Saturday and Sunday rain chances would jump-up!  But at least for now, we’re not biting on that weather “solution” for the weekend just yet.

In the extended outlook, we bring slight rain chances (about 20%) into the Monday forecast, with our next frontal passage on Tuesday generating showers and t-storms.

Monday, February 20, 2012

Rising Rivers...Good-Looking Fat Tuesday

By Jay Grymes & Steve Caparotta

We’re still looking at river flooding along portions of the Amite and the lower Tangipahoa. 

The Amite at Denham Springs is nearing an expected crest of just over 31 feet this evening, and should be back below flood stage by Tuesday evening.  The Amite at Bayou Manchac is expected to rise above the 9.0ft flood stage tonight, peak at around 10.0ft early Wednesday morning, then fall below flood stage by late Wednesday evening.

The Tangipahoa at Robert has been in flood since Saturday, and is approaching the expected crest of about 18 feet.  A slow fall should begin Tuesday morning, with that gage currently expected to drop below the 15.0ft flood stage on Thursday afternoon or early evening.

More river stages and forecasts are available here:

While many of us are still looking at standing water following Saturday’s big rains, Monday’s weather cooperated fairly nicely, with highs in the 60°s.  And it looks even better for “Fat Tuesday” as we stay dry and warm-up a tad!  Get your bead-gathering gear ready for a very mild Mardi Gras Day!

After just some high, thin cirrus through most of Monday, mid-level clouds have returned to the WAFB viewing area during the late afternoon.  Those clouds will stay with us for the night and into Tuesday morning, and we could see a little fog developing for the early morning as well.  Look for Tuesday’s sun-up temps in the low 50°s.

We’re expecting a mix of sun and clouds throughout the day on Tuesday, but a southerly flow will mean a big warm-up, with highs climbing into the low to mid 70°s for the day.

We’ll bring a slight chance of rain into the forecast for Wednesday afternoon.  The models are differing a bit for Wednesday, with a couple of models suggesting decent rain chances (say, 30% to 40%) for the afternoon and evening, while our in-house Titan9 model keeps Wednesday mainly-dry.  For now, we’ll split the difference with a 20% to 30% rain chance for metro Baton Rouge, with slightly higher rain chances closer to the coast.

Thursday looks to be wet for most of us as a quick-moving Pacific cool front slides through the state late in the day.  We could see a few lingering showers and clouds very early on Friday, but skies should clear during by if not before the afternoon.  Highs will drop from the mid 70°s on Thursday to the upper 60°s for Friday.

And the upcoming weekend outlook?  For now, we see no problems there!  Saturday will be a little cooler, with highs in the low to mid 60°s but with plenty of sunshine, and Sunday looks partly cloudy with highs in the upper 60°s.  The way it looks right now, it will be a rain-free weekend!

Friday, February 17, 2012

Heavy Rain, Severe Storms Possible Saturday

By Jay Grymes & Steve Caparotta

Today’s good news was the lack of rain in the area, as a warm front stayed well off-shore and the weak disturbances drifting in the upper-air flow simply didn’t have sufficient moisture to generate the passing showers that we had anticipated.  Indeed, most of us saw some sunshine during the afternoon, allowing highs to reach the 70°s.

The Krewe of Southdowns parade should go without a hitch.  We may see a patch or two of light rain in the area during the evening, but we’re keeping rain chances for Friday evening at less than 20%, and anything that does fall between now and midnight won’t amount to much.

By Saturday’s sunrise, it’ll be a different story ... and time for the rain gear. 

Officials for the Spanish Town Parade have delayed the start of that Mardi Gras tradition until 3:30-4PM -- a wise decision indeed.  In fact, don’t be surprised if they end up delaying the start of the parade just a tad more.

Our forecast calls for rains in the morning, with widespread rain and t-storms moving into the WAFB area from the west in earnest by late morning.  In addition to a FLASH FLOOD WATCH for the viewing area, Saturday’s stormy weather comes with a slight risk of damaging winds and isolated tornadoes, with the timing of the main threat of severe weather running between roughly 11AM and 3-4PM as the threat moves west-to-east.  The severe threat is a little higher for communities along and south of the I-10/12 corridor, but everyone in the WAFB viewing area should remain alert through the day.
(Don’t be surprised if a T-Storm or Tornado Watch is also posted by mid to late morning.)

Rain totals are likely to be in the 1” to 3” range for many of us, with isolated totals of 4” or more possible for those neighborhoods experiencing multiple passing t-storms through the day.  Not only could this produce localized flooding issues and roadway concerns, but several area rivers are running high already -- another couple of inches of rain in 6-12 hours could push several river-gaging sites above flood stage.

But here’s the silver lining: this looks like it may be a fairly quick-moving system, with much of the stormiest weather exiting the WAFB viewing area before dark.  In fact, the bulk of the rains could be over by or even before 7PM for many of us.

Clouds will linger into Saturday night as some “backside, wrap-around” flow brings in some mid-level moisture, but skies clear for a cool-but-sunny Sunday afternoon.

Lundi Gras (Monday) looks good.  We bring a 30% to 40% chance of rain back into the Mardi Gras holiday during the latter half of Tuesday, with better rain chances for Wednesday.

Good News, Bad News for Parades

(Note: the graphics in the post below are a somewhat lower quality than usual because I'm writing this from home late Friday morning)

Let's start out with some good news...

Today's forecast is turning out to be a bust in a good sense. Rain chances now look quite low through the day, which is good news for tonight's Southdowns parade. A few isolated showers can't be ruled out this evening, but any rain would likely be light. Look for temperatures in the low to mid 60°s for most of the parade.

Now the bad news...

As we warned you yesterday evening, a Flash Flood Watch has been posted for the entire WAFB viewing area, beginning at 6 a.m. and continuing through 6 p.m. on Saturday.

Flash Flood Watch in effect 6 a.m. - 6 p.m. Saturday. Courtesy: NWS New Orleans/Baton Rouge.
This morning's computer guidance is in very good agreement on bringing heavy rains into the area. The latest 2 runs of the NAM model forecast 2.03" and 2.13" of rain for Baton Rouge, while the latest 2 runs of the GFS forecast 2.71" and 1.71". A look at the RPM forecast below shows it has just about all of southeast Louisiana receiving anywhere from 2" to 4"+ of rain on Saturday (as indicated by the red and maroon shaded areas).

RPM model forecast rainfall. The red and maroon shades over most of SE Louisiana indicate 2" to 4"+ of rainfall.
The computer guidance is also now in good agreement on bringing widespread shower and t-storm activity into the area as soon as Saturday morning and continuing into at least a portion of the afternoon. Below is a look at 4 different computer model projections for Noon on Saturday.

RPM model projection for Noon on Saturday. The red and pink shades would likely represent t-storms.
GFS model forecast for Noon on Saturday.
NAM model forecast for Noon on Saturday.
ECMWF (European) model forecast for Noon on Saturday.
One trend worth monitoring today is that the models seem a bit slower in having the rains exit on Saturday. Most of our guidance yesterday showed things ending pretty quickly during the early afternoon; the latest runs indicate rains could continue into late afternoon before exiting.

The good news this morning is that Baton Rouge Police and the board of Spanish Town have made what I think is a very wise decision to move the start time of the parade back to 3:30 p.m. That still seems to be a close call in terms of getting wet, but I'm still somewhat optimistic that the worst of the storms will be through by then. We'll have to take another look at it this evening.

As I also mentioned last night, I still think it's quite possible that much of southeast Louisiana could be under a tornado watch by Saturday morning. The atmosphere will have plenty of wind shear to work with...the question is actually whether it's too much shear. There is also some question as to whether there will be enough 'instability' to drive severe storms, but I think there will be.

The Storm Prediction Center still has the area under a 'slight' risk of severe weather on Saturday. They actually have the 30% chance of severe weather contour just south of Baton Rouge. The 30% area in the map below means they're forecasting a 30% chance of severe weather within 25 miles of any point in that shaded area.

Probability of severe weather within 25 miles of a given point on Saturday from the Storm Prediction Center.

So, the bottom line here is that tonight's Southdowns parade should be fine. The later start time for Spanish Town gives them much better odds of rolling without incident, although we will have to continue to monitor the timing of Saturday's rainfall. Assuming Poseidon follows Spanish Town, I would expect that parade to be fine, although there will be an increasing threat of gusty winds as the night wears on behind a cool front.

Thursday, February 16, 2012

Wet Weather Returns Friday, Saturday

By Jay Grymes & Steve Caparotta

We spent just about all of Thursday under the clouds, but at least it stayed mainly dry.  Watching Titan9 Doppler radar throughout the day showed that storms were very active about 20-60 miles off the Louisiana coast, all tied to a quasi-stationary front that meandered over the northern Gulf.  Unfortunately, that same front, further energized by mid/upper-level disturbances passing from west-to-east, is going to make for a couple of wet days for the WAFB viewing area.

Clouds will continue over the region tonight, but we will remain mainly-dry into Friday morning.  Temps will dip into the mid to upper 50°s by Friday’s sunrise, with a few showers possible for the morning commute, mainly closer to the coast.  We could also see some pockets of fog in the morning, but widespread fog isn’t likely as winds should be running out of the east at about 5-10 mph by sun-up, limiting fog to wind-shielded areas.

As the day progresses, however, rain chances will go from 20% to 30% in the early morning to 60% to 70% by the afternoon.  Friday afternoon temps should climb into the low to mid 60°s.  While rain is likely, we don’t expect any heavy rains through the day – Friday will be an “over-running,” gray-sky day with mid-level clouds and a passing upper-air disturbance generating mainly light rain for metro Baton Rouge.  Most of us will see less than one-quarter-inch of rain on Friday, with higher totals possible closer to the coast.  But we expect little if any thunderstorm development on Friday, so even if it’s still raining Friday evening, those rains should be light enough to allow the Krewe of Southdowns to roll if they so choose.

Saturday?  That looks like a very different story weatherwise.

Right now, Saturday not only looks like a wet day, but it could be very wet. In fact, the National Weather Service is hinting at the possibility of a Flash Flood Watch being posted as soon as Friday afternoon or evening.

Projected rainfall on Saturday from our Titan9 RPM model. The model shows most of the WAFB viewing area receiving 1" to 3" of rainfall during the day, with the potential for locally higher amounts.

In addition, the NWS Storm Prediction Center (NWS/SPC) has the entire WAFB viewing area included under a “Slight Risk” for severe weather on Saturday.

Most, if not all, of the computer weather forecast models that we review have a low pressure center developing along that same stationary front in the Gulf late Friday, with that low tracking east-northeast into southern Louisiana during the day on Saturday.  Since the models seem to agree on the basics, the only question that remains is “how far inland” does that low track?  The farther inland it goes, the stormier the weather could become for metro BR.

Plot of low pressure center locations at Noon on Saturday from 4 different computer models. The 3 highlighted models (NAM, ECMWF, GFS) imply a threat of heavy rain and strong storms because of a track near or to the west of Baton Rouge.
Plot of low pressure center locations at Noon on Saturday from 4 different computer models. The highlighted model (RPM) implys a lesser threat of heavy rain and strong storms because of a track south of Baton Rouge.
And at least for now, the timing couldn’t be much worse for a noon kick-off the Spanish Town Parade.  Our Titan9 model gets the weather rolling by or before 11:00 am.  The “stormiest” of Saturday’s weather could be exiting the WAFB viewing area to the east by the mid- to late afternoon, allowing for better weather for Saturday evening parades across most or all of southeast Louisiana.

And it all quiets down after that: the weather looks great for Sunday and Monday, with only a slight chance of showers during the latter half of “Fat Tuesday.”

Weekend Parade Outlook

For the second year in a row, we're looking at potentially dicey weather for the final weekend of Mardi Gras parades in the Baton Rouge area. I'll start with a look at the Southdowns parade, scheduled to roll at 7 p.m. on Friday.

Most of our guidance is now in good agreement on good rain chances on Friday. However, there are differences in both the timing and the intensity. After examining several models, it appears as though most point toward light to moderate rains, although the NAM model generates about an inch of rain in Baton Rouge on Friday. At this point, I'll consider that an outlier and lean toward lower rain amounts on Friday.

For the Southdowns parade itself, I think we'll have scattered showers around south Louisiana, but litte if any lightning/thunder. So, with that said, the parade should be able to roll as planned, although it could be wet at times. Below is a look at parade time Friday from 4 of our computer models. As you look at the image below, it's important to note that the ECMWF ('European') model is at a lower resolution than the others, so it is likely overdoing the scope of the rainfall.

(a) Titan9 RPM model. (b) NAM model. (c) GFS model. (d) ECMWF model.
While I believe Southdowns will be able to roll without major incident, things aren't so clear for Spanish Town on Saturday. A wave of low pressure forming in the western Gulf of Mexico is expected to track toward Louisiana on Saturday. The track of the low will be key. A track near or west of Baton Rouge would likely bring active weather into the area, including the threat of some severe storms. A track to our south or east would keep the active weather away, with just some soaking rains expected.

The image below shows the same 4 forecast model projections for Noon on Saturday. Note that 3 of the 4 models below paint a rather ugly picture for parade time on Saturday. Those same 3 models all have the low tracking near or west of Baton Rouge, implying both a threat of heavy rains and a few severe storms. Any severe storms could produce damaging winds and even isolated tornadoes.

The one model that keeps the low to our south is our Titan9 RPM model. This is a model that we typically lean heavily on in the 24-48 hour forecast range. However, at this point I'd have to consider it an outlier, so I tend to lean more heavily on the other models painting a wet and stormy picture for the first half of Saturday. Keep your fingers crossed that the other models fall in line with our Titan9 RPM, but for now, we'll go with the consensus.

(a) Titan9 RPM model. (b) NAM model. (c) GFS model. (d) ECMWF model.
As mentioned, a track near or west of Baton Rouge would likely lead to a threat of severe weather. The Storm Prediction Center agrees, outlining all of southeast Louisiana under a 'slight' risk of severe weather on Saturday.

Severe weather threat from 6 a.m. Saturday to 6 a.m. Sunday from the Storm Prediction Center.
The other concern is the potential for heavy rains. Again, the track of the low pressure center will determine which areas get dumped on. Below is a rainfall projection graphic from our Titan9 RPM model from 6 p.m. Friday through 6 p.m. Saturday.

Titan9 RPM model rain projection from 6 p.m. Friday through 6 p.m. Saturday.
Remember from our discussion above, our Titan9 RPM model tracks the low well southeast of Baton Rouge. As a result, you see the heaviest rains in this projection extending from Terrebonne & Lafourche parishes into metro New Orleans. However, if you move the low track farther inland, closer to Baton Rouge, it would be fair to assume that stripe of heavy rain would be closer to Baton Rouge as well. In the graphic above, the light green and yellow shadings are indicating anywhere from 2" to 4" of rainfall.

While our Titan9 RPM model keeps rain totals modest around Baton Rouge, a glance at projections from our other models shows 1" to 2" forecasted during the day for Baton Rouge.

The weather looks rather 'iffy' for Spanish Town, but rains should start to wind down from late afternoon into the evening on Saturday. I think there's a decent chance that Poseidon could roll as planned, although there may still be some rain in the area. Below are the 4 model projections for parade time for Poseidon.

(a) Titan9 RPM model. (b) NAM model. (c) GFS model. (d) ECMWF model.
 We'll take another look at the latest model runs later this afternoon or evening...

Wednesday, February 15, 2012

Wet Tonight, Again Saturday

By Jay Grymes & Steve Caparotta

The rains have been a little slower to arrive for much of the WAFB viewing area than we had anticipated yesterday, but a look at Titan9 Doppler radar this afternoon makes it clear that the showers and t-storms are on their way!

For metro Baton Rouge, there is a “Slight Risk” for severe storms late this evening and into the pre-dawn hours of Thursday -- the threat arrives a little earlier for communities west of the ‘Red Stick’ and later in the morning for areas south and east of metro BR.  That severe threat will mainly be in the form of localized high winds, but we can’t entirely rule out the potential for isolated tornadoes.  And while hail doesn’t look to be a widespread issue, don’t be surprised by pockets of hail through the night.

A cool front will be working its way through Louisiana tonight and into Thursday morning, and that will be the lifting mechanism that fires-up some strong to severe t-storms and prompts our severe weather risk.  The rains should be over for most, if not all, WAFB neighborhoods by mid-morning on Thursday, but clouds will linger into the afternoon.  In addition, the so-called cool front won’t cool things off much at all, as we expect highs to return to the 70°s again on Thursday.

Unfortunately, Thursday’s advancing front will slow and eventually stall along our coastal waters and linger there into Friday.  That set-up, coupled with some upper level support, will keep the weather unsettled through most of Friday – that’s why we keep a 40% to 50% rain chance in our Friday forecast.

As we head into Saturday, the forecast guidance suggests that a low will develop along that same front over the northern Gulf.  At the same time, that front will begin to retreat to the north as a warm front with the Gulf low tracking towards the SE Louisiana coast.  With an upper-air disturbance adding to the equation and helping to boost regional instability, it sure looks like the better part of Saturday will be “wet.” 

In fact, at this point, the questions are, “how wet and how stormy?”

The answer will eventually be determined by the exact track of the Gulf low.  If that low moves up and over the coastal parishes, they could see rain on the order of an inch or more with thunderstorms.  Should the surface low stay along the coast or out over the water and move east, rain totals and the stormy-weather threat will be reduced.

Top-left: Titan9 RPM model projection for Noon Saturday. Top-right: GFS model projection for Noon Saturday. Bottom-left: ECMWF model projection for Noon Saturday. Bottom-right: NOAA/HPC rain projection from 6 p.m. Friday through 6 p.m. Saturday showing 1" to 3" of rain for most of south Louisiana.

Regardless, periods of rain seem to be a sure bet across the WAFB viewing area through most or all of Saturday and right into the evening.  And given Saturday’s expected cloud cover and cool temps -- topping out in the low 60°s -- let’s just say it won’t be the best weather day! 

But we’ll still salvage some good weather for the extended Mardi Gras holiday.  After morning clouds and a lingering shower or two early on Sunday, skies should be clearing for Sunday afternoon with highs in the 60°s.  Monday looks good -- under fair to partly cloudy skies -- with highs in the upper 60°s.  We bring a 30% to 40% chance of rain back into the forecast for the latter half of ‘Fat Tuesday’ as our next front approaches the region, with the weather clearing by Wednesday afternoon.

Tuesday, February 14, 2012

Rain Wednesday, Again For Weekend Parades?

By Jay Grymes & Steve Caparotta

The clouds and patchy fog exited most of the area early in the morning and the afternoon has been a beauty, although maybe not quite as warm as we expected.

Mainly clear skies this evening will give way to mostly cloudy skies by Wednesday’s sunrise, with morning lows running around 50° for metro Baton Rouge. But take note: you’ll need the umbrella by Wednesday afternoon. We’re expecting temps to climb into the 70°s during Wednesday afternoon as a warm front lifts to our north. This means that the WAFB viewing area will be in the “warm sector” of a storm complex, with our communities sitting east of an advancing cold front.

By “warm sector,” we mean that the air is warm and moist and usually rather unstable – for our region, “warm sector” air originates over the Gulf and moves northward. Unstability (unstable air) means that the air near the surface is primed to rise vertically and generate rain clouds and thunderstorms -- the greater the instability, the greater the threat for the potential for severe weather.

Scattered showers by or before Wednesday’s lunch hour will become rather widespread by the afternoon and into the evening, with thunderstorms on the increase during the latter half of the day as well. In fact, the NWS Storm Prediction Center (NWS/SPC) has most of Louisiana rated as under a “Slight Risk” for severe weather from Wednesday into Thursday morning as the unstable air is further energized by the approaching front to the west. We expect that front to be pushing through SE Louisiana during the early morning hours on Thursday, and as the front moves off to our east, rain chances during Thursday morning will decline.

The threat of severe weather on Wednesday serves as a reminder that we are approaching the peak of our severe weather season as we move from the late winter months into spring. A great way to stay informed and safe when severe weather threatens is to have a NOAA Weather Radio in your home.

At this time of the year a west-to-east moving front -- a cool or cold front -- usually means a noticeable drop in temperatures. But we’re not likely to notice much of a change in temps for Thursday as our current forecast calls for highs again in the 70°s for Thursday afternoon.

A modest cool-down comes by Friday, with highs topping out in the upper 60°s for many WAFB neighborhoods. But by the latter half of Friday, we bring rain chances back into the forecast.

We’ll need to watch this closely as we head into the big Mardi Gras weekend. For the time being, we’ll post rain chances at about 30% for Friday afternoon and evening, which could make things a little dicey for Friday night’s Southdowns Parade. With a little luck, the Friday night neighborhood frolicking will “roll” without a weather-hitch.

But an even bigger disappointment may be in the works for Saturday’s Spanish Town Parade.

Our Saturday outlook on Monday offered hopes of a mainly dry mid-day and afternoon for the parade, but the guidance as of Tuesday afternoon is far more gloomy for the latter half of the day. There’s still time to allow for adjustments for Saturday’s forecast as we progress through the work week, but as of today, Saturday is looking rather “wet” throughout, with rain possibly extending into early Sunday morning.

You can bet that we’ll be watching, because the WAFB Storm Team loves the parades of Carnival Season as much as you!

Monday, February 13, 2012

Rain Tonight, Warmer Days Ahead

By Jay Grymes & Steve Caparotta

Did you notice Baton Rouge’s record low (above) for today: 2°F -- Yikes!

That’s the all-time lowest reading ever for the Red Stick, beating the 8° many of you remember in 1989. And for you trivia buffs, the monster freeze of February 13, 1899 set records not only in Louisiana, but across a large portion of the Deep South. The event still claims the record for all-time lowest temps for more than a dozen states!

Reports from the time indicate that the Port of New Orleans was completely iced over and ice floes were spotted moving from the Mississippi River into the Gulf of Mexico. Mardi Gras fell on February 14th that year, making it the coldest Fat Tuesday on record in New Orleans, with a low temp of 6° and a high of only 25°! The parade route reportedly had to be cleared of snow and ice before Rex rolled.

So what was the lowest reading for the Bayou State during that event? How about -16°F in Minden, LA!

You can read more about the amazing outbreak of cold weather in 1899 here:
"The Great Arctic Outbreak and East Coast Blizzard of February 1899"

Well we had our brief taste of freezing weather over the weekend, and now we catapult back into the 70°s by tomorrow. But not before we deal with another round of rain. As of this afternoon, we’ve already seen a few showers, and rain becomes “likely” later this evening. But this will generally be light to moderate rain, and while a few might hear a rumble or two of thunder, most of us will see less than one-half-inch of rain through the overnight hours.

Our thinking is that the rain is out of the WAFB viewing area before Tuesday morning’s commute and bus rides, although the clouds may still be around. And with temps likely to stay in the mid to upper 50°s overnight and into Tuesday morning, the wet ground and relatively warm air will support some areas of fog early in the day. But the clouds move out quickly, as does the fog, with clearing skies by or before lunchtime and plenty of sunshine for the afternoon with highs in the low to mid 70°s!

After another morning start in the 50°s, showers and thunderstorms will return during the latter half of Wednesday, and continue into the early morning on Thursday. The Wednesday/Thursday event looks wetter and probably stormier -- we’ll have to see how the forecasted dynamics develop after tonight’s round of showers.

We cool things down as we head into Mardi Gras weekend. For now, we’ve got isolated showers for Friday night with scattered showers lingering into Saturday morning.

So ... for the Krewe of Southdowns (Friday evening), just be sure to carry an umbrella although you may not really need it. And while we may see some rain for Saturday morning, we’re hopeful that all will be quiet before ‘Spanish Town’ rolls ion Saturday!

Friday, February 10, 2012

Goodbye Rain, Hello Freeze!

By Jay Grymes & Steve Caparotta

It’s been a very soggy Friday and the clouds kept temps in the 40°s for much of the day. But there is some good news for the ladies of Artemis as the rains are exiting the BR metro area -- although it will remain cloudy and cool, it will be mostly rain free for tonight’s Krewe of Artemis parade!

Some light rain is still falling to the east and south of BR as of 4PM, but even that will be exiting to the east through the evening. By Saturday morning, the clouds will be clearing out as well. Look for Saturday’s sun-up temps in the low 40°s for metro BR. Sunshine will be the rule of the day for Saturday, but a cold air mass and northerly winds will mean highs only in the low 50°s.

So for Saturday, it’s dry but cool for the array of parades across the area – so just dress warm and get ready to catch some cold beads!

Then comes what may be the weekend’s BIG weather story: a morning freeze for Sunday! A FREEZE WATCH and a HARD FREEZE WATCH for Sunday morning currently include virtually all of the WAFB viewing area. A “hard freeze” seems possible, if not likely, for many WAFB communities near and north of the LA/MS state line.

Truth is, we are overdue for a freeze. We’ve only seen about half the normal number of freezes thus far this winter, with no “hard freezes” (temps at or below 26°) recorded at Metro Airport yet this winter. In fact, Sunday morning’s chiller will be Metro Airport’s first freeze since January 15th.

Thankfully, the core of the Arctic air mass delivering Sunday’s freeze will be pushed quickly to the east, which means only one freeze-day with this event. High temps will return to the low 50°s on Sunday, with Monday’s low in the mid to upper 30°s for the ‘Red Stick.’

Our forecast for next week indicates unsettled weather returns, with rain chances posted for just about each day of the work week. But you will also notice a warm-up in our forecast, with highs returning to the 70°s by Wednesday.

Stay warm and enjoy the weekend!