Wednesday, March 18, 2015

Keep the Umbrellas Handy

By Jay Grymes & Steve Caparotta

WAFB First Alert Quickcast:

- just some passing showers this afternoon and evening
- only modest rain chances (30%) for Thursday & Friday
- rains return for a wet weekend ahead

Today’s rains were a considerably less impressive than we had anticipated yesterday.  The evening commute was much drier than expected - - no complaints there - - and what rains that did develop will be out of the area this evening.

Today’s limited rains were the result of an upper-level low that “opened up” (became less defined) as it tracked across Texas, Oklahoma and Arkansas.  Unlike what most of our guidance was suggesting even as late as this morning, it simply did not generate much in the way of activity in our area, and Doppler radar and lightning detection made it clear that there were very few thunderstorms.  It’s moving to the northeast rather quickly now, and most of the rain in the WAFB viewing area will be done by or even before 8:00pm.

Expect a dry wake-up for Thursday under mostly cloudy skies with patches of light fog at sunrise.  We won't go entirely rain-free, but Thursday and Friday look drier than today: we'll call for a 30% rain chance, mainly the afternoon variety, for both days. Look for temperatures on both days to remain above normal: morning lows in the low 60°s, afternoons up around 80° or so for most of us.

Over the past two days we’ve also mentioned an upper-low just off the Southern California Coast.  This system will become better organized -- likely becoming a “cut off” low -- over the next day or so as it moves east along the U.S./Mexico border.  This Desert Low has the potential to be a much more active rainmaker for us … and is shaping up to deliver a disappointingly wet weekend ahead.  Timing of the weekend rains is still an issue, with the American GFS model suggesting rains could start arriving as early as late Friday or early Saturday.  The European model holds the rains off until the latter half of Saturday, and is the ‘drier’ of the two models as well.

We’ve still got a couple of days to fine-tune the weekend outlook, but for now we’re going with “rain likely” for both Saturday and Sunday.  If the GFS is closer to correct, Saturday could be a wet mess just about all day long, with periods of rain on Sunday.  The ‘Euro’ makes Sunday look like the wetter of the two days, but neither day being a n all-day wash-out.  More importantly, at this time neither of these two extended-range models is suggesting significant severe weather for the weekend nor exceptionally heavy rain.

As of early this morning, The NWS hydrometeorologists at the Weather Prediction Center (WPC) are calling for regional totals on the order of 1” to 2” for most of the WAFB viewing area between today and Monday morning.  The WPC’s rain forecast shows an increasing gradient from the coast to the northern portions of the viewing area, with totals of 2” to 3” possible for some of our SW Mississippi counties.​

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