Tuesday, November 17, 2015

Severe Weather Threat Arriving

We've warned you for close to a week about to the potential for severe weather and that threat appears to be playing out. A Tornado Watch is posted for metro Baton Rouge and SW Mississippi through 8 p.m., with a Watch for Acadiana and SW Louisiana through 4 p.m.

You may think that with the watch set to expire at 8 p.m. locally, that would mark the end of the severe weather threat. However, we're likely to either see an extension of that watch or a new watch issued later tonight. We are essentially facing the potential for two separate rounds of severe weather. The initial round will be in the form of scattered strong to severe storms well in advance of the cold front. These 'discrete' thunderstorm cells will have a somewhat better chance of becoming tornadic, although any tornadoes are still expected to be isolated.

The second, primary threat of severe weather will accompany a squall line. Typically squall lines produce more in the way of straight-line wind damage, but isolated tornadoes will remain possible. It is the squall line that will impact most of the area late tonight. Radar trends suggest that the models may be a little too slow in moving the squall line eastward, but look for the primary threat window to be roughly 8 p.m. - midnight for metro Baton Rouge.

A Flash Flood Watch also remains in effect for all of our viewing area through 10 a.m. on Wednesday. 

We don't expect rains as bad as what we experienced in late October, but widespread totals of 2" to 4" can be expected, with locally higher amounts possible.

Stay with the First Alert Storm Team throughout the remainder of today and tonight as we track the approaching storms. We'll have coverage on air, online and in our free weather app. Also, make sure you have a way to receive weather warnings before going to bed tonight. We highly recommend a NOAA Weather Radio which will sound an alarm if a warning is issued for your area.

Thursday, October 29, 2015

Halloween Gloom Compliments of Mother Nature

The threat of rain and storms has forced most communities around the area to move Trick-or-Treating to Friday night (click here for updated times). While there may not be any real legal punch behind the move, the not-no-subtle suggestion from area leaders is the right move to make.

It's simple -- Friday likely stays dry while Mother Nature may outdo ghosts and goblins with the fright factor on Halloween.

Heading into Saturday, the threatening weather has also prompted the 10/31 Consortium to move their planned parade from a 2 p.m. start to 9:30 a.m. instead. That should be good enough to avoid the worst of the weather, but showers will be possible, even during the morning hours.

Outside of impacts to Trick-or-Treating and other Halloween events, the big story for the weekend will center around rain amounts and the potential for additional flooding. Most of our computer guidance paints anywhere from 1" to 4" of rain across the area through the weekend. However, our in-house RPM model has had some runs today with bands of even higher amounts. The latest available run as of Thursday evening delivers widespread 3" to 5" totals, with locally higher amounts.

Most area rivers have already crested or are near crest tonight, but we'll need to keep an eye on the potential for additional rises over the weekend, depending on exactly how much rain we receive.

At this point, we don't expect widespread severe weather, but a few isolated strong storms will be possible, particularly Saturday afternoon and evening. The Storm Prediction Center has our area under a 'marginal' risk for severe weather.

We'll be here through the weekend to keep you updated on the expected rains and any strong storms that may develop. You can also track the rains on your smartphone or tablet using our free weather app:

Apple download: http://shout.lt/42Rq

Android download: http://shout.lt/42Q8

Tuesday, October 27, 2015

Weekend Soaking in Perspective...and Another Round Ahead?

By Steve Caparotta

Were you among the plethora of south Louisiana residents begging for some rainfall through the first few weeks of October? I was certainly in that crowd, growing tired of running my sprinkler to keep my lawn and garden from wilting in the dry and warm weather. But as they say, be careful what you wish for.

In a remarkable turn of events, we went from 'extreme drought' in some locations to dealing with flooding in the course of just a couple of days. In fact, the most recent Drought Monitor that was released last Thursday, October 20th, had more than 50% of Louisiana classified as being in an 'extreme drought', with over 13% of North Louisiana under the worst classification of 'exceptional drought'. It's fair to say the map below will see significant changes when a new update is released this Thursday.

As it turns out, a stretch of 24 days without measurable rain in Baton Rouge and much of the surrounding area and an overall dry stretch since the beginning of September turned out to be a blessing this past weekend. While we certainly dealt with some localized flooding in urban areas and continue to monitor rising rivers, it could have been much worse had there been any rain of consequence in the prior days and weeks.

How big of a rain event did we see this past weekend? For most of the area, it was the most significant multi-day rain since Tropical Storm Allison produced flooding in 2001. Sunday's rainfall ranks as the 5th largest single-day total in Baton Rouge in records that date back to 1892!

And the 2-day rain total for Saturday and Sunday in Baton Rouge ranks as the 6th largest 2-day event since 1892.

It's also remarkable to consider that through October 23rd, Baton Rouge Metro had only recorded a trace of rainfall. Three days later, 2015 stood as the third wettest October on record!

One other way to measure a rain event is by using a tool that climatologists call 'recurrence intervals'. Without getting into the dirty (and boring to many) details, recurrence intervals are a statistical measure of how frequently a given location can expect certain rain amounts over a given duration. Using a NOAA tool available online, we find that the 2-day rain total of just under 11 inches in Baton Rouge is a roughly 1-in-25-year event. In other words, people in Baton Rouge can expect to see rains like this past weekend roughly once every 25 years when averaged over a LONG period of time. Another way of looking at it is that there's a 4% chance in any given year of seeing a 2-day rain like this past weekend.

Recurrence intervals for rainfall in Baton Rouge. Source: http://hdsc.nws.noaa.gov/hdsc/pfds/pfds_map_cont.html?bkmrk=la
While most of our neighborhoods are beginning to dry out, rivers are still rising and we'll see additional problems through the week for those who live along or near rivers. And the bad news? It looks like we've got more rain on the way for the weekend.

The rains will be somewhat of a double-whammy, not only arriving over the weekend, but potentially turning into a real issue for Trick-or-Treaters and Halloween parties. There's still some uncertainty in the timing of the rains over the weekend, but it looks like the wet weather will begin to arrive by Saturday afternoon and continue into Sunday.

The map below shows that NOAA's Weather Prediction Center is already forecasting an additional 2" to 4" of rain for much of our area over the weekend.

One more thing to note that we've already mentioned at times in our weathercasts. One of the strongest El Niño events on record is ongoing in the Pacific. History tells us that during El Niño events, fall and winter tend to see above-normal rainfall along the Gulf Coast. With that in mind, it's quite possible that these rain events will only become more frequent in the coming months. The currently 3-month outlook for Nov-Jan from NOAA's Climate Prediction Center is in line with that thinking, calling for above-normal chances for above-normal precipitation in our region.

Stay dry, everyone, and count on the WAFB First Alert Storm Team on air, online and on your mobile device for the latest on any storm systems headed our way.

Friday, July 3, 2015

Scattered Storms Return for the Holiday Weekend

By Jay Grymes & Steve Caparotta

July 3rd WAFB First Alert Quickcast:

- back to scattered afternoon t-storms for the independence Day weekend
- drier and a little warmer for next week

Happy 4th to you and yours!

We doubt that anyone is complaining about our back-to-back dry days, thanks to high pressure at the mid and upper levels putting the clamps on afternoon thundershower development.

Unfortunately, the “lid” comes off the atmosphere over the weekend and we return to scattered afternoon showers and t-storms for both Saturday and Sunday. In fact, we’re leaning towards “rain likely” for Saturday (rain chances at 50% to 60% for Saturday afternoon), and there is a potential for a few strong to severe storms in the WAFB area over the two-day span.

The upper-level high (a mid/upper-air ridge, the “lid” on the pot) that put the brakes on afternoon rains yesterday and today will give ground over the weekend. That will let our moist and unstable Gulf air do its thing: build mid-day and afternoon showers and storms without an inhibitor to slow their vertical growth. Neither day will result in all-day rains for your backyard, but we expect a pretty active radar depiction for both afternoons as individual t-storms build, move and subside through the day. If you’ve got outdoor plans on either day, make sure that you have an indoor or under-cover option ready to go.

After muggy morning starts in the low to mid 70°s for both Saturday and Sunday around metro Baton Rouge, look for temperatures to climb into the upper 80°s to around 90° before the clouds and rains knock the temperatures back through the afternoon.

As for the Saturday evening “Fireworks on the Levee,” we expect the rains to have dissipated by showtime, but we could still have isolated rains in the area as late as 7:00 or even 8:00pm. We’re thinking that temperatures for the 9:00pm showtime will be in the upper 70°s to low 80°s on the levee.

Into next week, the ridge returns, taking rain chances back down into the ”isolated” category for just about every day next week -- yep, too bad the ridge had to retreat during the weekend. With the drier pattern in the forecast for next week, plan for muggy morning sunrises in the low to mid 70°s for most WAFB communities, with highs in the low 90°s just about every day.

Thursday, July 2, 2015

Mainly Dry Again for Friday

By Jay Grymes & Steve Caparotta

July 2nd WAFB First Alert Quickcast:
- hot, breezy and mostly dry for Friday
- scattered showers & t-storms expected for both weekend days

Okay, our “mainly dry” forecast for today took a big hit in a number of neighborhoods before 7:00am thanks to a band of mainly-light showers draped over the viewing area. Those showers fizzled out by or before mid-morning and the gray cloud deck had largely thinned before lunchtime. With the thinning clouds, mid-day and afternoon sunshine took temperatures into the 90°s for the afternoon.

Even as late as 3:00pm this afternoon, Doppler was “all clear” across the WAFB viewing area. A rogue, spotty shower or two might pop-up during the late afternoon or early evening, but we expect that just about everyone stays dry into the evening and overnight too.

Our Friday forecast calls for another mainly-dry day like today … with the big exception being no morning showers like some of us experienced this morning. After a muggy Friday morning start in the low to mid 70°s for many WAFB communities, we’ll climb once again into the low 90°s for Friday afternoon, with spotty showers, at best. Add in the afternoon humidity and that low 90° reading will ‘feel like’ 100° or more at the peak of the afternoon heat. Then it’s a warm and dry Friday evening and mostly fair skies into the night.

Out mostly-dry Thursday and Friday are courtesy of a western U.S. upper-air ridge building just a bit farther east. That ridge has pushed drier and slightly warmer air into the middle levels over the Bayou State -- and that serves as a rain-cloud inhibitor.

Unfortunately, the dry spell doesn’t hold through the weekend. The ridge softens and retreats westward allowing our locally-unstable air a better chance to build vertically during the afternoons: bigger afternoon cumulus clouds usually means more rain-clouds and better rain coverage. We’re still not too concerned about any kind of severe weather threat for either Saturday or Sunday, but we’ll go with rain chances at 40% to 50% or so for both days. Of course, with those elevated rain chances, we can’t rule out one or two strong storms on either afternoon.

So be ready to dodge the rains during both afternoons. We don’t anticipate all-day rains in either case and not everyone gets wet each day … but have a plan to get out of the weather should storms roll through your neighborhood. The good news is that we expect Saturday’s mainly-afternoon rains to be out of the way for Saturday evening’s fireworks and festivities.

Headed into next week, upper-level ridging builds back over the area, knocking rain chances back to around 20% to 30% for just about every afternoon. (Too bad that isn’t the cast for the weekend, eh?)

Tuesday, June 30, 2015

Scattered T-Storms Again on Wednesday

By Jay Grymes & Steve Caparotta

June 30th WAFB First Alert Quickcast:

- scattered afternoon showers & t-storms return for Wednesday
- isolated rains for Thursday & Friday
- back to a summer routine for the July 4th weekend

Looking for WAFB’s Weather App?  Find it here:
- Apple users click here: http://shout.lt/42Rq
- Android users click here: http://shout.lt/42Q8
.. or text WEATHERAPP to 99009 …

And for yet another day, some fairly strong t-storms rocked parts of the viewing area.  Unlike last night’s late-night storms and the action last Tuesday and Wednesday, these storms were not out of the north and northeast.  However, they were still quite energetic and lightning-laden, fueled by our very most and unstable Gulf air.  What’s more, they got an additional boost from a pair of features working together: a sea-breeze-like wave heading inland and what appears to be a broad-but-weak non-tropical disturbance moving to the west-northwest over the western Gulf.

Bottom line: a very active middle of the afternoon for metro Baton Rouge and western Livingston Parish, sections of the Felicianas and points west including parts of Pointe Coupee, Avoyelles and St. Landry parishes.  Once again, the most noteworthy aspect of these storms was the lightning - - which is credited with power outages and even one or more fires.  But we can’t ignore the reports of small hail from WAFB viewers as well as locally-heavy downpours that produced more rounds of street flooding.

The action will wind down into the evening and most of us will stay dry through the overnight and early morning hours on Wednesday.  We could see a few showers down near the coast for Wednesday’s sunrise, but the morning commute for metro BR should be a dry one for just about everyone.  Plan for a muggy, partly-to-mostly cloudy start to Wednesday with morning temperatures in the mid 70°s.

For Wednesday afternoon, here they come again: 50% rain chance with highs getting up to around 90° before the rains arrive. 

The weather gets much quieter for Thursday and Friday, with rain chances for both days currently posted at 20% or less.  Both days start off in the mid 70°s for the Red Stick and afternoon highs reach the low 90°s for most, with a few neighborhoods potentially sneaking into the mid 90°s.

And into the Fourth of July weekend, we return to something fairly typical for this time of year: morning starts in the low to mid 70°s for the metro area, afternoon highs in the low 90°s, and scattered mainly-afternoon t-showers for both days.

Friday, June 26, 2015

More Rain This Weekend

By Jay Grymes & Steve Caparotta

June 26th WAFB First Alert Quickcast:

- weekend cool front still on the forecast board

Today was yet another afternoon with scattered showers and storms … but the action was less substantial than what we saw on Thursday and nothing at all like the big boomers and excessive rains of Tuesday and Wednesday.  Today was something more “normal” for a summer day in the viewing area.

There is a change coming this weekend in the form of a summer cool front.  We can’t call summer fronts “rare” but they certainly aren’t very common.  During the winter and spring, we can expect to see five or six frontal passages -- sometimes even more -- each month, on average.  By comparison, during the summer season, that number drops to something closer to an average of one or two passages per month.  And often, our summer fronts don’t push all the way through the area: they stall near or along the coast and sit there until they fizzle-out.

That is precisely what we are expecting this weekend: a cool front will slide south out of the U.S. Plains and reach the WAFB area by Saturday afternoon and evening.  Then it simply stalls along or near the coast for the remainder of the weekend.

If that front would continue southward and move out over the Gulf, we would get a nice change in our weather.  A completed frontal passage would deliver slightly cooler temperatures and, even more welcomed, a big drop in our local humidity.  (90° afternoons don’t feel so bad if the air is less humid).  Unfortunately, our guidance is suggesting that the weekend front will stall somewhere along or near the coast late Saturday and then linger there into Monday before dissipating.

Fronts usually mean rain in the local forecast no matter what time of year.  So our weekend cool front will be a focus for rains on Saturday afternoon and evening -- by adding extra lift to our typical hot, humid and unstable sub-tropical Gulf air.  Then, with the front lingering near the coast into Sunday, we’ll keep “rain likely” in the overnight and morning forecast for our viewing area.

In the spring, a frontal set-up like this could mean some nasty weather and another round of potentially large rain totals.  Fortunately, summer fronts along the Gulf Coast tend to be less energetic than their winter and spring counterparts.  That said, we’ll still get showers and storms with this frontal boundary and we can’t rule out a few strong to severe storms as it settles over the area.  But with the front over the area at night rather than during the heat of the day, the threat for severe storms is reduced somewhat.

The rains will continue into Sunday morning, but rains on Saturday afternoon and into the overnight hours will take a big bite out of the local atmosphere’s storm energy, with rains winding down as we head towards Sunday mid-day and afternoon.  We’re not ready to say “rain free” for Sunday afternoon, but it’s looking like isolated showers with the majority of WAFB neighborhoods staying dry into Sunday afternoon and early evening.  In addition, clouds and morning rains on Sunday will slow the daytime warm-up, with just about all of us topping out in the 80°s for Sunday afternoon.

So how “cool” will it get?  Most viewers in the coastal parishes will get little or no relief from the humidity, which means not much change in terms of morning lows on Sunday and Monday.  For the northern half of the viewing area, if the front can make its way as far south as the coastal zone, at least some communities north of the I-10/12 corridor could slip into the upper 60°s on one or both mornings. 

We’ll go with morning minimums on both days close to 70° for metro Baton Rouge: not much of a change but at least a couple of degrees cooler -- and a little less humid -- than the past several days.

As for next week, our current extended outlook calls for a return to our traditional summer routine at least through mid-week: morning lows in the low to mid 70°s, most afternoons climbing to 90° or more, and scattered mainly-afternoon showers and storms just about every day.

How about the tropics?  Dead quiet.  While there are a few tropical waves running in the easterly tropical flow (and that is normal), none of them show any potential for development.

Eyes to the skies on Saturday afternoon … but here’s hoping that you get to enjoy the weekend!