Thursday, March 29, 2012

Grab the Umbrella for Friday!

By Jay Grymes & Steve Caparotta

As of 5PM, we still haven’t seen the rain that we expected for the day. Titan9 Doppler radar is showing a stray shower here and there across the viewing area, but not the 30% coverage that we anticipated yesterday.

But a wider view of the radar screen shows a broad area of rains extending from East Texas into central and northern Louisiana, along with a well-defined storm system sliding ENE across the northwestern Gulf. This set-up paints a better picture for increasing rain chances by early Friday and well into the day.

Plan on scattered showers with a few t-storms for Friday morning’s commute, with scattered rains extending through the morning and into the afternoon. We’ll start the day in the low 60°s across metro Baton Rouge, with afternoon highs climbing to around 80° or so for the day. Rains should be subsiding by Friday evening’s drive home, but there will still be a few showers in the area.

Our weekend forecast now looks noticeably “drier” compared to earlier in the week. We’ll go with only spotty showers (less than 20% chance) for Saturday afternoon with a modest 20% rain chance posted for Sunday afternoon. With the reduced rain chances -- and the dip expected in the overall cloud coverage -- we expect highs for both days to climb into the mid 80°s.

The outlook for next week suggests that a trailing cool front will slide from west-to-east across the Bayou State late Monday into the morning hours of Tuesday. Based on the current guidance and expected timing of the frontal passage, we’re posting a 30% chance of rain for Monday afternoon and evening, with a 40% to 50% chance (or better) through the night into the early hours on Tuesday.

Skies should clear rather quickly during the latter half of the day on Tuesday, with cooler and less-humid days for both Wednesday and Thursday.

But the big news for many of us is the improved weekend outlook -- is that barbeque pit ready for some springtime outdoor cooking??

Wednesday, March 28, 2012

Better Rain Chances Ahead

By Jay Grymes & Steve Caparotta

Highs in the low to mid 80°s, a few more clouds, a tad more humid and a handful of showers streaming in from the Gulf during the afternoon -- the forecast for today shaped up just about the way we saw it on Tuesday.

Our forecast for the next two days gets progressively “wetter” -- we’ll call it a 30% rain chance for Thursday with a 40% to 50% rain chance on Friday. Keep the rain chances at 40% for Saturday, then back them down to a modest 20% for Sunday. So it gets wetter over the coming days, but not a total wash-out. And the rain totals through the weekend don’t look all that impressive, with the NWS Hydrometeorological Prediction Center calling for rain totals on the order of one-half-inch or less through the weekend.

NOAA / HPC forecasted precipitation through Monday morning.

Our rain chances over the coming days will not be related to frontal activity, as the jet stream and associated surface lows will remain well to our north through the weekend. Instead, the rains will be courtesy of abundant moisture in the low-level of the atmosphere -- thanks to “return flow” off the Gulf -- coupled with the occasional passage of mid/upper-air disturbances providing lift to that moisture to generate clouds and get the mainly afternoon rains going.

The added cloud cover and passing rains will mean that afternoon highs for the coming days will be a few degrees cooler than our recent run in the mid 80°s, but that will most likely be offset by the local humidity, keeping the “feels like” temps higher than the thermometer readings.

Our next “cool” front is currently slated for arrival late Monday or early Tuesday - - of course, we will be tweaking the timing in the coming days. But it’s looking like the trailing end of a frontal system could be sweeping through the state around that time, providing modest rain chances for late Monday and early Tuesday. Forecast guidance suggests a minor dip in temperatures with that frontal passage, with dry weather expected for mid-week.

Tuesday, March 27, 2012

Stays Warm, More Humid

By Jay Grymes & Steve Caparotta

If you were outdoors during the afternoon, I’ll bet you sensed that slight but notable increase in humidity!  Although the thermometer said that Tuesday afternoon was about the same as Monday, it sure seemed warmer.  Not unpleasant -- just not as comfortable as the last couple of days.  Thankfully a light breeze through the afternoon kept the air from taking on that hot, muggy and “still” feeling that we know will be here soon enough.  Yes, summer is not too far away.

And be ready for the air to get slowly-but-progressively more humid as we head deeper into the work week.

The good news is that we don’t see any kind of threats in terms of severe weather for the next several days ... in fact, right now it looks like we’ll be free of active/severe weather through the weekend and into well into next week!  But that does not mean we’ll stay rain-free.

With the set-up of a steady “return flow” - - inflow of low-level moisture and warmth off the Gulf - - through the next five days or more, we’ll add enough Gulf moisture to the air to fuel some afternoon showers, with an occasional rumble of thunder as well.  But even with those occasional passing showers in the coming days, most of us will get through the entire weekend with little in the way of accumulations.  Current NWS Hydrometeorological Prediction Center rainfall projections suggest that most of us will see something on the order of under one-half inch of rain between Wednesday and Saturday.

NOAA / HPC forecast precipitation through Sunday morning.
We’re thinking only a stray afternoon shower or two (less than a 20% chance) for Wednesday and Thursday, with those percentages rising to 20% to 30% for Friday.  For now, we still think that Saturday has the best rain chance for your neighborhood over the coming days.

Even the rains that do develop on Saturday and Sunday are likely to be the scattered, rather brief variety of showers and thundershowers.  Most won’t last very long, so don’t cancel any weekend plans!

The other story is that we’ll stay warmer-than-normal through the week.  Look for highs in the 80°s with morning minimums in the 60°s for the week.  The increasing humidity -- increasing dewpoints -- will limit overnight cooling, and that’s pointing to muggy mid-60°s for morning lows by the weekend.  The added humidity will also mean better chances for early morning fog over the coming mornings, especially in the “usual suspect” areas.

Tuesday, March 20, 2012

Flash Flood Watch Wednesday

By Jay Grymes & Steve Caparotta

East Texas and western Louisiana have been dealing with local flooding, thunderstorm winds, and at least two tornadoes (in Sabine & Natchitoches parishes) this afternoon.

And that same mess is headed our way ... slowly. Very slowly.

We’ve seen passing showers across SE Louisiana and SW Mississippi through the afternoon, and that will continue into the evening hours, but the main line of storms remains well to our west. In fact, our in-house Titan9 model is even suggesting that the heaviest weather may not arrive until well after sunrise on Wednesday.

Titan9 RPM model projection for 7 a.m. on Wednesday showing heavy rains still to the west of Baton Rouge.
But when it does arrive, it will start a long run of wet weather that will extend through the remainder of the day and into Thursday.

Given this slow-moving forecast, the National Weather Service has issued a FLASH FLOOD WATCH for the entire WAFB viewing area. The main activity should be winding down by the morning or mid-day Thursday, but we could still see a few lingering light rains into late Thursday or even very early Friday before the clear-out really sets in.

The guidance is mixed in terms of just “how wet?” it gets in the viewing area, but at this point we certainly can’t rule out storm-event rain totals on the order 2” to 4” with localized totals approaching 5” or more. Fortunately, most of our viewing area has recovered nicely from the big rains of last week. Now, that doesn’t mean we won’t see some flood issues around the region, with a few river gages potentially reaching flood levels. But all in all, we don’t see this event becoming anything like the nasty flood-maker that developed last week in Acadiana.

And once we get this mess out of the way, we should head into a nice looking weekend with a run of “dry out” weather that extends into next week.

Monday, March 19, 2012

Windy Tuesday...Heavy Rains Midweek

By Jay Grymes & Steve Caparotta

Trivia buffs: the ‘astronomical’ start of spring -- the Spring, or Vernal, Equinox -- occurs overnight at 12:14am CDT. Are you ready to join the “Egg-Balancing Olympics?”

It’s been a breezy Monday under mostly cloudy skies and our forecast keeps the clouds and the breezes with us through the night and into Tuesday morning. The continued inflow of Gulf moisture and warmth means another sunrise start on Tuesday in the mid and upper 60°s for most of us, with the low-level winds sufficient to minimize any concern for widespread morning fog.

We’ll stay under mostly cloudy skies through Tuesday, with winds picking up and running sustained in the ‘teens and 20s (mph) with gusts occasionally in the 30s! We’ll also introduce a slight chance of rain in the afternoon forecast -- 20% to 30% -- mainly in the form of showers but some of us could hear a rumble or two of thunder. Highs on Tuesday will once again return to the 80°s.

Titan9 RPM model projection for 1 p.m. Tuesday showing isolated showers and t-storms in our area, with heavy rains in east Texas.
Our forecast for the week calls for progressively wetter weather, with the highest rain chances arriving Wednesday and Thursday, but with a true ”dry-out” not kicking-in until the weekend. The southern end of a slow-moving storm system will creep across Texas tonight and tomorrow and likely take all of Wednesday and Thursday to cross the Bayou State.

The weather over portions of the Southern Plains has been rather active already today, with Thunderstorm and Tornado Watches posted during the afternoon. The NWS Storm Prediction Center puts the western half of Louisiana under a “Slight Risk” of severe weather for Tuesday morning into early Wednesday, and our thinking is that we’ll remain under a “Slight Risk” for Wednesday into Thursday.

The driver for this run of active weather is an upper-level “cut-off low” which has become separated from the main upper-level jet stream. With the upper-level low “cut-off” from the polar jet stream, it really doesn’t have a steering mechanism to move it along. Instead, it is expected to drift over the Southern and Central Plains for the next few days. Given this set-up, the surface storm system and frontal complex associated with that cut-off upper-low will also be a slow mover -- hence the slow, prolonged march of the stormy weather from west-to-east.

This slow-moving system could become a real headache for portions of east Texas, the ArkLaTex and the western half of Louisiana over the next few days. Preliminary rain forecast totals from our in-house Titan9 RPM model are indicating widespread totals in excess of 3” to 5” by noon on Thursday for areas from Baton Rouge westward, with totals running as much as 7” to 10” or more near the LA/TX state line!

And given the slow eastward progression of this storm system, some WAFB communities could still be seeing rains well into Friday. The NWS Hydrometeorological Prediction Center is suggesting that most of the WAFB viewing area could see totals of 2” to 5” by week's end.

Thankfully, the weekend should show much improvement across the area, with clearing skies on Saturday giving way to a beauty of a Sunday.

Thursday, March 15, 2012

Dense Fog Advisory Friday Morning

By Jay Grymes & Steve Caparotta

A DENSE FOG ADVISORY goes into effect later tonight, and don’t be surprised to see morning Fog Advisories posted for Saturday and Sunday as well.

Our forecast is simple: more of the same! We’ll be staying warm and mainly dry for Friday and right through the weekend into at least the first part of next week. That means mornings in the 60°s with locally-dense fog likely, and highs in the 80°s with a stray shower or two, but mainly-dry afternoons and evenings.

Daily temps will continue to average around 8° to 10° or more above normal through the next several days, as ridging aloft combines with surface high pressure over the Southeast U.S. to keep us warm and mainly dry into at least the early to middle part of next week.

Clockwise circulation around the surface high pressure to our east will continue to produce onshore flow -- “return flow” -- and that means mild-to-warm and moist low-level air inbound from the Gulf. At the same time, subsidence -- sinking air that warms as it descends -- resulting from the upper-level ridging overhead will only add to the mid-day warming. And it looks like that set-up remains in place until at least Monday or Tuesday, possibly even into Wednesday.

So how “warm” has it been? For the first half of March, temperatures at Baton Rouge’s Metro Airport are averaging nearly 7° above normal, ranking as the “warmest” first half of March since 2006 (and ranking among the top six first halves since 1930).

And what about temperatures for the year-to-date? We know it has been a very mild winter, and the data support that: temps for January-thru-mid-March (76 days) are averaging about 60° -- ranking among the 4 “warmest” runs since 1930 for the first ten weeks of the year!

Wednesday, March 14, 2012

Feeling Like April or May!

By Jay Grymes & Steve Caparotta

Whether you think of spring as beginning at the onset of March or you’re a purist that waits until the Spring Equinox (on March 20th) before declaring the onset of the season, there’s no questioning that we’re enjoying spring-like weather this week.  In fact, temps this week will be as much as 10° (if not more) above normals for mid-March -- running closer to the normals for late April or even early May as seen in these 4 p.m. readings around the area!

And certainly few if any of us will complain much about a spell of mainly dry weather, even if it means running the air-conditioning more than we might like to!

Don’t look for any significant weather systems to impact the lower Mississippi Valley before the early to middle part of next week.  It looks like we are locked into a late spring weather pattern, with high pressure centered off the mid-Atlantic Coast and a “return flow” pattern that will keep the low level flow coming in from the southeast and south.  This “Gulf Return” pattern means continued inflow of Gulf moisture.

Look for morning minimums in the 60°s each day, with fog returning for each morning drive. In fact, a Dense Fog Advisory has been posted for much of the area from late tonight into Thursday morning.

Afternoon highs will climb to 80° or more each day, with daytime heating and the moist Gulf air being just unstable enough to allow for spotty to possible isolated afternoon and evening t-showers -- like those that bubbled up near Donaldsonville and over sections of East Baton Rouge and East Feliciana parishes on Tuesday evening.  But all in all, rain chances each day -- right through Sunday -- will be around 20% or less.  Not enough for a region-wide wet day any time this week, but over the course of the next five days or so, you may get a shower or two in your backyard.

Why no frontal systems over the coming days?  Right now the Polar jet stream -- U.S.’s main storm track during the winter and early spring -- has retreated to the north, keeping active weather systems over the northern tier of states and along the Canada/U.S. border.  The way things look right now, that pattern should start breaking down as we head into the weekend, with the Polar jet developing a ‘dip’ (a trough in the upper-air flow) over the eastern Pacific and U.S. West Coast.

Truth is, it is still a little too early to be certain about how the upper-air flow changes in the next four to five days, but if this outlook does indeed develops, we should anticipate a possible frontal system moving into the lower Mississippi Valley along a Tuesday/Wednesday time frame.

So enjoy the warm days and get ready for what should be a decent St. Patty’s Parade day on Saturday!

Tuesday, March 13, 2012

Drying Out, Warming Up

By Jay Grymes & Steve Caparotta

Acadiana and the rest of South Louisiana began drying out today -- a welcomed, and in some cases, a much-needed reprieve from the stormy weather that extended from Sunday night into Monday night.  Most of our local WAFB Weather Watchers reported storm totals on the order of 1” to 2”, with a few getting upwards of nearly 3” of rain for the event -- a considerable amount of rain in its own right but a far cry from the 10” to 15”+ that swamped portions of Acadiana! Some of the more impressive final totals include 14.18" from a USGS gauge at Bayou Vermilion near Carencro, 13.21" from a weather observer in Carencro, and 8.03" in Butte La Rose.

So how long will the dry weather persist?  Our thinking is that while we could see a spotty shower or two pop-up on Titan9 Doppler radar just about any day this week, we’ll stay with a mainly-dry forecast right into the weekend.
The weather stories for the rest of the work week will be the potential for areas of dense morning fog and afternoon highs that climb to 80° or more -- about 8° to 10° above mid-March normals.  This week looks like it will be free of any frontal passages across the Deep South.  The Central Gulf Coast will be dominated by “Gulf Return flow” -- southeasterly and southerly winds bringing mild-to-warm and moist air off the Gulf into the Bayou State.  That steady inflow of Gulf air will be enough to keep morning minimums around 60° or more for metro BR (and warmer closer to the coast) as well as supply the moisture to feed the early morning fog.

As the weekend approaches, we’ll need to keep a watch on the possibility of increasing winds.  The synoptic outlook (the national forecasted weather pattern) heading into the weekend puts a large dome of high pressure along the Atlantic Seaboard while an extended frontal system mover through the Rockies towards the western Plains.  Such a set-up would promote an increase in the southerly flow off the Gulf into the central and eastern U.S. by Sunday and early next week.

And for you trivia buffs, earlier this month we noted that the 2011-2012 winter was among the ten warmest on record for the Baton Rouge area.  NOAA’s National Climatic Data Center just announced that the 2011-2012 ranks as the fourth “warmest” winter for the nation as a whole, based on records dating back to 1895 (117 winters).  For Louisiana, the winter ranked as the 15 “warmest” since 1895, and the “warmest” winter since 1998-1999.

Monday, March 12, 2012

Stormy Monday!

By Jay Grymes & Steve Caparotta

What a run of weather for south Louisiana!

From tornado touchdowns around Jennings late last night ... to rain totals of 10” to more than 15” just north of Lafayette ... to an array of severe weather warnings and flood advisory statements throughout the day today ... this has been one of the busier days in the WAFB Weather Center in quite some time.

Doppler rain estimate through late Monday afternoon showing 10" to 15" of rain or more just north of Lafayette. In Carencro, over 10" of rain was recorded in a 6-hour period.
Even as we head into the late afternoon, there are still clusters of strong thunderstorms rolling through parts of south Louisiana, and we will be closely watching Titan9 Doppler radar for the next couple of hours, at least.  One bit of good news thus far is that there have been no reports of fatalities or serious injuries with this outbreak of stormy spring weather -- let’s hope that holds up through the evening!

A combination of features led to Monday's torrential rains. The primary culprit was a nearly stationary 'outflow boundary' stretching from just south of New Orleans to just south of Baton Rouge to just north of Lafayette. You can think of this outflow boundary as something similar to a mini cool front, helping to serve as a focus for shower and t-storm development. The boundary was actually triggered by the storms we saw late Sunday night.

Working in conjunction with the stalled outflow boundary were upper-level winds that were essentially moving parallel to it in a west-to-east fashion. This allowed storms to continue to develop and move over the same areas -- something we call a 'training' effect in weather.

We do have some better weather news ahead, especially for those overwhelmed with today’s stormy weather, as all of this mess should settle down as we head into the middle to late evening hours.  We’ll stay under a mostly cloudy sky through the night, and we’ll trade out the rainstorms for fog by Tuesday morning.  In fact, some of that fog could be quite dense in many locations by the morning commute.

Tuesday’s sunrise temps will be in the 60°s for just about all WAFB neighborhoods, and the day will be one of in-and-out sunshine.  It will be quite warm with highs climbing into the low 80°s, and we can’t rule out a spotty shower or two, but the day should be mainly dry.

We are anticipating fog for each of the next three mornings, at least, with sun-up temps running in the low to mid 60°s through the coming 7 days.  In fact, the entire week shapes up to be mainly dry and rather warm: highs each day from Wednesday through the weekend will be around 80°.

At this time, we don’t expect any significant frontal activity along the central Gulf Coast through the work week, or even the weekend for that matter.  A “return flow” set-up (SE and southerly winds) of Gulf moisture will be the rule, helping to maintain warmer-than-normal weather by mid-March standards, yet also keeping the air just moist enough to support an infrequent, spotty afternoon shower just about every day.

As we approach week’s end, we may see the winds start picking up as a pressure gradient develops with high pressure over the Atlantic Seaboard and a deepening low pressure system moving through the western states.

Flood Concerns

Torrential rains have impacted parts of south Louisiana since late last night, particularly in areas just north of Lafayette. As of late Monday morning, serious flooding is being reported around portions of Carencro. Carencro Police have reported flooded homes requiring the rescue of stranded residents. A middle school bus also got stranded in high waters, forcing the Lafayette Parish Sheriff's Office to assist in rescuing 16 students. Sections of I-49 in both directions north of Lafayette have also been closed because of high water.

Doppler radar makes it easy to see why that area is dealing with serious flooding, with estimates that 10" to 12" or more of rain has occurred since late last night. In fact, a USGS rain gauge at Bayou Vermilion near Carencro reported over 10 inches of rain in just 6 hours!

Doppler radar rain estimate through mid-morning on Monday.
The culprit for this morning's heavy rains has been a nearly stationary 'outflow boundary' left behind by last night's storms. The boundary is serving as a focus for new storm development this morning, and with little movement in the boundary itself, we are seeing a 'training' effect with the storms -- meaning storms are developing and moving over the same areas like train cars on a track. The threat of heavy rains is increasing around metro Baton Rouge as we get closer to lunchtime because this boundary is essentially overhead and heavy storms are moving in from the west.

The duration of heavy rains is very difficult to forecast in events like these with 'training' storms, but I definitely think some street flooding will be possible as we head into the early afternoon hours. Additionally, an isolated severe storm is possible. In fact, as of this writing, the storm approaching Iberville Parish in the image above is showing some rotation.

We will be monitoring developments throughout the day and will bring you any updates as needed. In the meantime, be sure to follow the rains with our Interactive Radar. Also, don't forget to download our Titan9 weather app for your smartphone: WAFB Apps

Friday, March 9, 2012

Improving Weather on Saturday

By Jay Grymes & Steve Caparotta

The time to SPRING FORWARD with your clocks is rapidly approaching (officially at 2:00am Sunday, as we lose an hour).  And we remind you that this is also a good time to check the batteries in your home smoke detectors and the back-up battery power for your NOAA weather radio!

Friday’s high of 72° is a bit misleading as it came in the first hours of the day.  With the cool front having moved over the coastal waters, many WAFB neighborhoods slipped into the 50°s by mid-day and stayed there through the afternoon.  For most of us, the significant rains ended by late morning although a damp air mass and a low cloud deck continued to deliver mist and patches of fog through much of the mid-day and afternoon hours.
Thankfully, last night’s active storms over central Louisiana stayed contained to the north of metro BR for the most part, with the front losing its punch as it moved south.  Doppler radar estimates and Weather Watcher reports indicated that most WAFB communities, especially those near, south and east of metro BR, received less than one-half-inch of rain (as of mid-afternoon).  However, radar-estimated totals over the Felicianas and Wilkinson and Amite counties were impressive, running as high as 2” to 3” in some locations!

24-Hour rain estimate showing the heaviest rains occurred in the Felicianas, northern Pointe Coupee, and parts of SW Mississippi.

Looks like the serious rains have ended for most of us for the rest of the afternoon, this evening and overnight.  There still remains some light rain over the southern parishes, and that might continue into the evening closer to the coast.  We can’t rule out a passing shower or two this evening and overnight as the atmosphere remains moist and an upper-level disturbance over Texas heads northwest.  So don’t be surprised by periods of mist this evening, but we really don’t anticipate any thing more than a few spotty sprinkles and little or no accumulation.

The upper-level low we’ve talked about so much during the latter part of this week remains well to our west -- in fact, it appears to have drifted farther to the west today and is now over the Desert Southwest! 

That is good news, especially for Saturday.  With that upper-low so far to the west, and the current Texas disturbance expected to be out of the picture by tomorrow, Saturday’s forecast looks much improved.  We’ll start Saturday in the upper 40°s for metro Baton Rouge with afternoon highs reaching the low 70°s.  Although most of the day will be in-and-out of the clouds, the day will stay mainly dry.

Indeed, Saturday will be the “get outdoors” day of the two-day weekend -- good news for Saturday morning’s Susan G. Komen “Race for the Cure” ... or a quick trip to unload some of those household materials at EBR’s (residents only, please) Household Hazardous Materials Day collection (9am-1pm) at BR’s Memorial Stadium.

Rains return to the forecast for Sunday and Monday, with isolated rains still possible into Tuesday.  For now, the remainder of the week looks pretty good!

Thursday, March 8, 2012

Rains Arriving Friday

It’s been another breezy, warm, and even somewhat muggy day across the area. Afternoon temps have risen into the lower 80°s in many locales, following a morning start that only saw temps drop into the upper 60°s and lower 70°s. In fact, those morning readings are closer to normal highs for this time of year. Winds this afternoon have gusted over 30 mph in many locations.

Peak wind gusts through 4 p.m. Thursday.
A few showers have dotted our Titan9 radar screen through the afternoon and will continue to do so into the evening. However, rains shouldn’t be much of a concern if you have plans to get out for dinner or anything else. Just grab an umbrella in case you get caught under one of the brief downpours.

Rain chances will increase sharply during the overnight hours as a cool front approaches from the north. Showers and t-storms are likely by the time we hit the morning commute on Friday. Fortunately, severe weather doesn’t appear to be much of a threat, nor does heavy rain. Yes, we could see some locally heavy downpours, but flooding-type rains aren’t really expected. Most of us will likely see under an inch of rain on Friday, but any storms could produce locally higher amounts.

Titan9 RPM model projection of rain totals through Saturday morning. The blue shades indicate under an inch of rainfall, while green shading indicates 1" to 2".
Friday’s high temps will likely occur during the overnight (near 70°), with daytime readings stuck in the 60°s thanks to clouds, rainfall and the passage of a cool front.

If you’ve been paying attention to our forecasts this week, you may remember that we’ve discussed the potential for Friday’s front to stall nearby. It now looks like the front will slip well to our south, with a couple of notable consequences: a somewhat cooler start on Saturday morning, but also much lower rain chances than initially expected on Saturday.

While we could still have a few isolated showers in the area on Saturday morning, the Komen Race for the Cure will likely avoid any major weather problems. You may actually want some long sleeves early on Saturday with temps expected to be in the lower 50°s.

We also remind you the Saturday is Household Hazardous Materials Day for East Baton Rouge Parish residents.

Good rain chances return to the forecast from late Sunday into Monday as our next system approaches from the west. Again, widespread severe weather is not expected at this point, but there are some indications we could at least see a strong storm or two. We’ll take a look at that again tomorrow.

Wednesday, March 7, 2012

Rain Chances on the Rise

By Jay Grymes & Steve Caparotta

We open with a simple mid-week reminder that this coming weekend marks the start of Daylight Saving Time -- we “spring ahead” at 2:00am Sunday morning, losing an hour in the process.  We’ll send a couple more reminders through the week.

As we expected, a little warmer and a tad more humid for Wednesday afternoon, adding more cloud cover and even generating a handful of spotty afternoon sprinkles rolling through the area.  Winds were running in the double-digits through the day as we drifted in and out of the clouds, letting WAFB community temps climb into the upper 70°s to near 80°.

Our thinking for Thursday is much the same weatherwise, although we anticipate a few more showers during Thursday afternoon.  Many of us will begin the day in the 60°s with a little patchy fog, but we think that even winds in the early morning will be sufficient to minimize the fog coverage.  Look for highs on Thursday around 80° and winds will again be out of the south and SE running in the ‘teens with occasional gusts in the 20s.

The upper-air pattern we described yesterday still holds, with an upper-level low associated with the current western U.S. upper-level trough becoming “cut-off” (separated from the main Polar Jet Stream flow).  That cut-off low will likely meander over the Southern and Central Plains from Friday into Monday; at the same time a surface front approaches the viewing area into the weekend.

Titan9 RPM model projection for Noon on Friday showing a cool front moving into the area, sparking showers and t-storms.
This set-up will make for a run of unsettled weather days.  And ... this set-up also has the potential for a “big bust” in the weather forecasting department.

If the upper low positions itself relatively close to Louisiana -- say over central and east Texas -- it will help promote a “wetter” weather pattern.  However, if the low sets-up shop over western Texas or farther to the north in western Oklahoma or Kansas, then the frontal signature will be much less impressive over the weekend.

For now, we’re playing it cautious and prepping our audience for a Friday-through-Monday that tends to be on the “wet” side of things, keeping rain chances at 50-50 or better for all four days.  That does not mean all-day washouts, but it does suggest that showers and t-storms could be more the rule than the exception through the period.

Hopefully, we’ll get to fine-tune our weekend outlook in the next day or so.

A Stormy Sun!

Massive solar flares erupting from the sun over the last few days have garnered quite a bit of attention from space weather enthusiasts. While most of us are unlikely to notice any impacts from the flares, they can have significant effects on portions of our planet.

Last Friday, March 2nd, an active sunspot region -- named 'Region 1429' -- emerged into view on the surface of the sun. A trio of flares erupted from the sun from Friday to Sunday, with the largest occurring Sunday night. The video below from NASA's Solar Dynamics Observatory (SDO) shows the eruptions.

Solar flares are rated on a scale whereby 'A' is the smallest, followed by B, C, M, and X - the largest. Sunday's flare was rated an X1.1.

It appears as though the mass of charged particles from Sunday's flare only dealt a glancing blow to earth, with the most significant burst likely just missing our planet.

Tuesday evening, an even larger flare was spotted bursting from the same active region of the sun and it was given an X5-class rating. NASA released a video similar to the one above showing Tuesday's massive flare.

These 'solar storms' can be rather difficult to understand, so let me try to breakdown the few elements involved.
  • First, fairly soon after the solar flare occurred Tuesday evening, there were some 'radio blackouts' reported on the sunlit side of the earth. These impacts are confined to high frequency (HF) radio signals, primarily impacting some broadcast entities and navigation frequencies for aviation. The radio blackout was given an R3 ('strong') rating -- see scale here.
  • The flare also produced a large coronal mass ejection (CME). NOAA space weather forecasters are saying the peak impacts from this CME will likely begin within a few hours, give or take, of daybreak Thursday our time.
  • Potential geomagnetic impacts:
    • NOAA forecasting G3 ('strong') storm levels -- see scale here.
    • Increased aurora, although very unlikely to be seen this far south.
    • Problems with GPS systems
    • Electrical power grid interference (power companies have been alerted)
    • Flights near the poles may be diverted because of navigation system interference
  •  Solar radiation impacts:
    • NOAA forecasting S4 ('severe') storm levels -- see scale here.
    • Astronauts aboard the Space Station must be monitored.
    • Satellites can experience significant problems.
I sat in on a conference call with a NOAA space weather expert this morning who says that the active sunspot region will continue to have the ability to provide significant impacts over the next week or so. In fact, he said forecasters are expecting more large solar flares (and CMEs) in the coming days.

Here are a few links with more information:

Tuesday, March 6, 2012

Warm, More Humid Days Ahead

By Jay Grymes & Steve Caparotta

Two things to consider with today’s forecast: (1) the weather just doesn’t get much better than what we’ve enjoyed the last couple of days, and (2) weather like this usually doesn’t last long.

You’ll start to note the first signs of chance by Wednesday, with more clouds throughout the day.  Although it will still be a relatively comfortable day, you almost certainly notice a modest increase in humidity levels.  As we saw today, winds will again stay up on Wednesday thanks to a decent pressure gradient across the central Gulf Coast.  Wednesday will start off warmer -- with sunrise temps in the 50°s.  Afternoon highs will climb to around 80°F.

More clouds and more humidity by Thursday means a very slight chance of rain by the afternoon -- less than 20% -- but a sure signal that the lower atmosphere is moistening up.

By Thursday morning, a western storm system will have worked eastward, with an elongated frontal system extending from eastern Canada across the Great lakes and southwestward into Texas.  Normally at this time of year, such a set-up would usually mean that the front slides into and through Louisiana early in the weekend.

Titan9 RPM model projection for 7 a.m. Thursday showing a cool front attempting to approach from the west.
This time, however, the models seem a bit mixed as to how it all plays out.  Most of the guidance suggests that the southern end of the frontal system will slow -- even stall -- for one or more days over Texas, setting sections of northern and central Texas up for some very heavy rains.  At the same time, with the front to our north and east, the WAFB viewing area will be in the “warm sector” with unstable air, keeping the weather “unsettled” for Friday and the weekend.

An upper-level trough currently in the Pacific Northwest will be the driver for this developing weather scenario.  Where the confusion comes into the forecast process is the potential for the trough to spin-off a “cut off” upper low -- a circulation feature that stays located over the Central or Southern Plains rather than progressing to the east with the main jetstream flow. 

The eventual evolution of an upper-level trough currently along the West Coast will be a big determining factor in how wet our weekend turns out and how long the rains last.
These cut-off lows can be pesky weather-makers and make forecasting more difficult as they can meander for days before finally moving out of the region.  A shift in location to the east or west during its meandering can make all the difference between “dry” and “stormy” weather locally.

Some guidance even suggests that the weather remains “wet” into the early part of next week.  Hopefully the picture for the weekend will get a little clearer in the coming day or so, but for now we suggest that your weekend plans include dodging some raindrops.

Monday, March 5, 2012

Warming Up

A brief taste of cooler weather we enjoyed this weekend into Monday morning will quickly come to an end over the next 24 hours. Tuesday will provide another comfortably cool start in the upper 40°s, but afternoon highs will again reach the mid to upper 70°s under mostly sunny skies.

Strengthening southerly winds will result in milder mornings and a continuation of warm afternoons through the remainder of the week. Those southerly winds will also pump more moisture (humidity) into the area in the coming days, adding a ‘mugginess’ factor as the week wears on.

The next couple of days should remain dry, but a few showers are possible by Thursday afternoon and evening as our next storm system approaches from the west. The extended outlook features the potential for a somewhat prolonged run of unsettled weather as a cool front possibly stalls nearby into the weekend.
Titan9 RPM model projection for 7 a.m. on Thursday. The cool front seen out to our west will likely stall nearby into the weekend, resulting in a stretch of unsettled weather.

For now, we’ll call for fairly high rain chances beginning on Friday and continuing through the weekend, but there is some potential for the more significant rains to stay just to our west on Friday and Saturday. The location of the most significant rains will be highly dependent on where the front stalls, so we’ll continue to examine that and update our forecast over the next couple of days.

The 5-day rainfall outlook from NOAA’s HPC (Hydrometeorological Prediction Center) also supports the idea of significant rains staying to our west through at least Friday, with their projections showing most of the area receiving around a half-inch or less of rainfall through Saturday morning:

While we will be watching out for some rain later this week, the good news is that there appears to be little threat of significant severe weather anywhere across the U.S. That's a welcome change following a pair of dealy tornado outbreaks last week.

The graphic below shows the number of confirmed tornadoes so far in each state from Friday and the number of fatalities in green. Unofficially, it looks like we're at 49 confirmed tornadoes so far for Friday. The record for a single day in March is 59 and that could easily be surpassed in the coming days as the National Weather Service continues to finalize damage surveys.

Number of confirmed tornadoes in each state (number superimposed on tornado symbol) and fatalities (in green) from March 2, 2012 storms.

Friday, March 2, 2012

Storms Tonight, Cooler This Weekend

By Jay Grymes & Steve Caparotta

It is proving to be another disastrous and deadly day for communities ranging from northern Alabama into Tennessee, Kentucky and northward into southern sections of Illinois, Indiana and Ohio. As of 4PM, the NWS Storm Prediction Center (SPC) showed a preliminary count of 48 touchdowns, with today’s twisters scattered over more than a half-dozen states. In addition, there have been nearly 300 additional reports of wind damage and large hail today, stretching across large tracts of the Mississippi, Ohio and Tennessee river valleys.

Tornado reports as of late afternoon Friday.
Wind, hail, and tornado reports as of late afternoon Friday.
It’s the second major outbreak this week -- and just to make this clear, this is NOT a result of global warming.

Although the truly frightening weather outbreaks have remained to our north and northeast, we are not entirely in the clear here in the WAFB viewing area. The SPC has included a large portion of northern, central and western Louisiana in a Severe Thunderstorm Watch until 9PM, and all WAFB communities along and north of the I-10/12 corridor are included under a SLIGHT RISK for severe weather through this evening and into Saturday morning.

As we write this, a cold front with a pre-frontal squall line is marching southeast across the Bayou State. Our in-house Titan9 model suggests that the main storm energy will reach the metro area sometime after midnight, then continue to move east and southeast through the early morning hours.

Titan9 RPM model projection showing the cool front and an associated squall line moving through metro Baton Rouge just after midnight.
We’ll stay warm, muggy and breezy as the rains move in, with temps running in the upper 60°s and 70°s prior to the frontal passage. By sun-up on Saturday, the stormier weather should be south and east of metro Baton Rouge, although some lingering rains could remain over metro BR with thunderstorms still over portions of SE Louisiana and the SE coast.

Temps will drop considerably after the front moves through and the rains should be all but over by mid-day Saturday. But a north-to-NW wind along with a cloud deck that may be slow to clear will keep Saturday much cooler, with highs likely to top out in the low 60°s!

On the other hand, Sunday will be a mighty-fine early March day. The day starts out very cool, with a low near 40°, but sunshine under clear skies will allow for a nice warm-up through the day as highs rebound into the upper 60°s for the Red Stick.

A warming trend will continue into the work week, with dry weather expected at least through Wednesday. In the extended outlook, models are hinting at our next frontal passage on Friday.

Thursday, March 1, 2012

Changes for the Weekend...

By Jay Grymes & Steve Caparotta

Thankfully the winds stayed up last night, keeping widespread dense fog from developing as we had expected. And through the day today we had some nice breaks in the clouds, even though a few neighborhoods still managed to deal with a shower or two through the day. Given the warm and moist Gulf air mass in place and the mid-afternoon spells of sunshine, the thermometer rose into the 80°s across the viewing area, with a few locations tying or breaking records for today’s high.

Friday will be yet another day where many, if not all, of us will see neighborhood temperatures return to the 80°s - - a fourth day in a row at a time when highs normally are much closer to 70°! We’ll start Friday with mostly cloudy skies and patchy fog, but it looks like the winds will again be active enough to limit any concerns of widespread dense fog. Winds will stay up through the day on Friday, with mid-day winds running occasionally climbing into the ‘high teens’ and ‘twenties’ (mph). Mostly cloudy skies through the day will provide a few showers by the afternoon and early evening - - we’re going with a 30% rain chance for that window of time.

Titan9 RPM model projection for 6:30 PM Friday showing just a few showers in the area. Rain chances are expected to increase late Friday night into Saturday morning.

The cool front we’ve talked about for a couple of days is still on track to arrive early Saturday, although the latest run of our in-house RPM model has slowed the system’s forward speed a tad. Rain will likely start arriving in the Baton Rouge metro area by or before midnight, with the frontal boundary expected to slide through the metro area by or before mid-morning.

We note a “SLIGHT RISK” for severe weather for WAFB communities north and northeast of metro BR between about 8PM Friday and 6AM Saturday. The main severe weather energy will remain far to our northeast, stretching from northern Alabama into southern Ohio. For now, we’re expecting most Weather Watchers to report from about a quarter- to a half-inch of rain with Saturday’s front, with a few possibly topping the one-inch mark where t-storms are a little more productive.

The Storm Prediction Center has a 'moderate' risk of severe weather posted for portions of the Tennesse and Ohio valleys on Friday. They've also outlined that same area in an enhanced 45% chance of severe weather within 25 miles of any given point. A 'slight' risk of severe weather extends down to the LA/MS state line.
Clouds may linger a bit behind the front, but we should see some clearing skies by mid-afternoon on Saturday. It will be noticeably cooler as well, with or current forecast calling for a high in the mid 60°s for the Baton Rouge area! Sunday is shaping up to be a March beauty: sunny skies with a cool morning start near 40° but a mild afternoon in the upper 60°s.

Monday through Wednesday look like superb early spring-like days, with highs in the low 70°s. And for now, even Thursday looks pretty good, with only spotty afternoon showers and a high in the mid 70°s.