Friday, August 23, 2013

Good Rain Chances This Weekend

By Jay Grymes & Steve Caparotta

Radar and satellite continue to highlight the easterly wave in the northern Gulf as it continues to slowly move from east-to-west.  The National Hurricane Center still gives this disturbance very little chance of developing into a tropical cyclone (a depression or tropical storm), but it is shaping up to be a rain-maker in the coming days for the southern parishes.
Due to its slow movement -- in fact, a tad slower today than we expected -- the WAFB viewing area remained under the influence of the “front” side (west side) of the wave -- this is the drier side of the disturbance.  With easterly waves, subsidence (sinking air) dominates the area ahead of the wave axis; generally the area behind the trough (the east side, the back side) is the wetter region.
So for today, we were a bit drier around the area than we had anticipated.
By Saturday, however, the wave will have moved far enough to the west to put southeastern Louisiana and SW Mississippi on the back side of the trough, enhancing rain chances for Saturday afternoon and into Sunday.  Still, we don’t anticipate an all-day rain for either day.  What we do expect is that the wave’s influence will be greatest for the coastal parishes, with its impact lessening as we head inland over the viewing area.
For Saturday, we think “rain likely” for our southern parishes, with rain chances running around 50-50 or so for those near and along the I-10/12 corridor.  Rain chances could be slightly lower still along the LA/MS state line, running around 40% to 50%.
For Sunday, we’re thinking about a 40% rain chance along the I-10/12, with those percentages running a little lower closer to the state line and a little higher closer to the Gulf.
What do those percentages tell us?  Don’t expect a “weekend wash-out” although you will want to check the radar on both days if you’re planning to spend time outside.  Nor are we anticipating widespread “big” rain totals over the weekend.  The southern parishes will likely see some decent totals, with some coastal locations possibly getting as much as 2” to 3” of rain through the weekend.  The current NWS Weather Prediction Center (WPC) forecasts call for weekend rain totals to fall off quickly from the coast to more inland sites, with current WPC projections running under 1” for the weekend for just about all locations north of the I-10/12.
By Monday, the wave should be inland over Texas.  And elsewhere in the tropics ... nothing of concern, at least for the time being.
Into next week, the extended outlook continues to call for a building upper-level ridge over the center of the U.S. with surface high-pressure expanding over the lower Mississippi Valley.  That combination should not only lead to drier days by mid-week, but also a warm-up.  In fact, if this scenario pans-out, some WAFB neighborhoods could see a return of the mid-90°s by the middle to end of next week.
So stay dry … and here’s hoping that you get to enjoy the weekend!

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