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!

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