Tuesday, May 13, 2014

More Rain on Wednesday

By Jay Grymes & Steve Caparotta

WAFB Storm Team QuickCast:

- isolated showers & patchy fog for Wednesday’s wake-up
- showers & t-storms likely for Wednesday PM
- looking good for Thursday through Sunday
Not a lot of change in our forecast thinking from yesterday.  As expected, there has been a scattering of showers this afternoon with occasional rumbles of thunder, but many WAFB neighborhoods stayed dry.  While there was no severe weather, we did receive several pictures of a funnel cloud spotted near Erwinville around 5 p.m. This was likely a 'tropical funnel' -- a type of funnel cloud that forms in humid airmasses, but usually doesn't touch ground or cause significant damage.
Funnel cloud near Erwinville. Credit: Julie Arceneaux
We've been watching a rainy mess in Texas over the past 24 hours thanks to a spring front that has been creeping from west-to-east across the western half of the Bayou State today.  The slow-mover has prompted the NWS to issue a series of Flash Flood Watches over the past two days, extending from northern Arkansas to NW Louisiana and into South Texas.  While there have only been a handful of Severe T-Storm Warnings issued with the frontal system over the last 48 hours, local-heavy rains have resulted in a number of Flood Warnings in Texas and even western Louisiana between yesterday and today.
However, even with its slow forward advance, the front has moved too far to the east with respect to its upper-level trough.  In effect, the front has lost a good bit of its upper-air support (‘lift’) which has resulted is subsiding rains through the day.  However, the upper trough will begin a more progressive move to the east tonight and early tomorrow, bringing life back into the surface front.
At this stage, we are not overly concerned about another round of flooding rains nor do we anticipate a widespread severe weather event.   Still, we note that the NWS Storm Prediction Center (SPC) does include neighboring SW Mississippi under a "Slight Risk" for severe weather on Wednesday.
Our latest in-house RPM model does suggest that we could see a few stronger t-storms, especially for areas north of the east-west interstate corridor.  In addition, while our currently shows most of the WAFB viewing area as receiving less than an inch of rain between now and Wednesday evening, a few areas could see as much as 1" to 3" where the stronger storms develop.  Those kinds of rains could generate another round of rises along our regional rivers and streams, but we think that the heavier rains will be isolated and localized, so that there is no real threat for the main channels -- like the Amite, Comite, Tickfaw and Tangipahoa -- to reach flood stages.
Our latest RPM model run clears things out fairly quickly, with skies over metro BR clearing by the evening hours.  And once the skies clear, we're all in for a nice spring treat.
Our forecast for Thursday through the weekend is not only dry, but quite pleasant in terms of temperatures and humidity.  A cool-and-very-dry Canadian air mass will deliver near-record to record lows on Thursday and Friday: low to mid 50°s for Thursday morning and upper 40°s to low 50°s for Friday's sunrise.  Highs on Thursday will top-out in the mid 70°s for metro Baton Rouge and only get up to around 80° or so For Friday.
And while temperatures (and low-level humidity) will show a slow rise through the weekend, the regional weather will still be rather pleasant by mid-May standards, making for a couple of good-looking "Get outdoors!" days.

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