Monday, March 18, 2013

Tricky Forecast Later This Week

By Jay Grymes & Steve Caparotta

Admittedly, this is shaping up as one of the tougher 7-day forecasts we’ve had to prepare in quite a while.  The guidance models are not in great agreement in terms of timing or intensity of wet weather during the coming week, especially towards week’s end and into the weekend.

We’ve got a cool front working from west-to-east this afternoon, but it doesn’t look like it will generate much, if any, rain for the WAFB viewing area.  We’re expecting the front to slide by late this evening, with the winds swinging around by or before midnight.  We’re anticipating a really nice day weatherwise for Tuesday, with mostly sunny skies accompanied by a noticeable drop in humidity compared to today.  We’ll start Tuesday off with clearing skies and sunrise temps in the 50°s and climb into the upper 70°s -- a day with a true spring feel.

For Wednesday, it looks like the clouds return and even bring a slight rain chance (about 20% or so) during the morning and mid-day hours as a weak disturbance rides west-to-east across the region.  It will be cooler too, with a morning start near 50° and afternoon highs only reaching the low 70°s.

Thursday currently shapes up with a sun/cloud mix through the day and a high only getting to around 70°.  For now we’ll go with a “dry” Thursday, but that may change with the potential for a few showers late in the day.

A stalled front draped across the Gulf coastal states will serve as the impetus for rains on Friday while a disturbance to the west gets better developed before arriving over the lower Mississippi Valley by Saturday.  This pair of features has us posting rain chances at roughly 50% for both Friday and Saturday, with a lingering 20% rain chance for Sunday morning.  Once all of that clears out we’ll really cool down – we’re calling for highs on Sunday and Monday in the 60°s and a forecast low for early Monday down into the 40°s.

So, with spring “officially” arriving at mid-week, we’ve had some questions about the threat for a late season freeze.  The climate statistics look like this:

For Baton Rouge, there is still about a 1-in-10 chance (10%) for another freeze this season.  The latest freeze in any year for the Red Stick was April 13, 1940 … when the temp briefly dipped to 31°.  Since 1930, Baton Rouge has recorded just two April freezes, the other occurring on April 4, 1987 (32°).

By comparison, there is still roughly a 1-in-3 chance for another freeze in McComb, where there have been a handful of April freezes over the last 60+ years (back to 1948).  In fact, there were 4 April freezes at McComb in 1987 and 3 in April of 1971.

And as our third example, Donaldsonville has only one April freeze in its time series back to 1930 -- the same April freeze that is on the record books for Baton Rouge: April 13, 1940.  Given its distance south of Baton Rouge, it comes as no surprise that Donaldsonville’s freeze chances over the next couple of weeks are less than 1-in-10.

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