Tuesday, November 11, 2014

Big Chill on the Way!

By Jay Grymes & Steve Caparotta

WAFB First Alert Quickcast:

- front moves through metro BR tonight
- a few light rains, cooler for Wednesday
- Arctic air mass delivers a “first freeze” for many on Friday

After a morning low in the upper 50°s (as we predicted), most Veterans Day ceremonies went off without weather issues. Doppler radar was showing a few pockets of mainly-light showers well west of metro BR during the afternoon and the day warmed considerably, with highs in the upper 70°s to around 80° for many WAFB communities.

A cold front continues to slowly push southward through the Bayou State this evening and overnight, but will still be stretched across the northern Gulf waters on Wednesday. Wednesday morning lows will be near 50° to the low 50°s for most of the WAFB area, running a little higher closer to the coast. But under the clouds and with a colder air mass taking residence, daytimes high only make the mid to upper 50°s. With the front still close and clouds lingering, we’ll keep isolated light rains in the Wednesday forecast -- rain chances for the day will sit around 20% or so, with the best chance for a shower or two coming during the first half of the day. Regardless, whatever and wherever rain does fall, it won’t amount to much and will provide no relief to the dry conditions in the region. 

(We anticipate that the U.S. Weekly Drought Monitor will officially acknowledge the onset of “drought” conditions for portions of the Florida Parishes with its Thursday 8AM release.)

While this mid-week front will be a disappointment in terms of delivering some needed rain, it will make its presence felt when the Arctic air mass behind it fully arrives. Fortunately, this will be more of a sideswipe than a direct hit in terms of a winter chill. We’ve been showing you the plunging temperatures to over parts of the northern U.S. over the past 24 hours, including some locations in the High Plains where temperatures dropped more than 50° in less than a 24-hour period! Thankfully, we’ll have nothing like that.

What we are anticipating, however, is the first fall freeze for much of the northern half of the WAFB viewing area. We’ll call for a sun/cloud mix on Thursday with a morning start in the upper 30°s for metro BR and an even cooler daytime high for Thursday in the low to mid 50°s. As of this afternoon, we’re calling for a Baton Rouge low near or below freezing on Friday morning with lows dipping into the upper 20°s near and north of the LA/MS state line.

We said this cold air episode would be more of a sideswipe rather than a long-lasting direct hit. But it will be cold: many get a freeze on Friday morning and highs on Friday afternoon struggle to reach the 50°s for some of WAFB’s northern viewers. And some of WAFB’s northern communities could flirt with another brief freeze for Saturday’s sunrise. Thankfully, most of us will get back into upper 50°s to near 60° for Saturday afternoon.

Heading into the late Saturday and Sunday, here comes our next frontal system … and this one looks like it has some potential to be a decent rainmaker. A low out of the western Gulf will meet-up with a cold front diving southeastward from the Plains. Based on the current guidance, that is a set-up for rains of an inch or more centered on Sunday. The Plains cold front will also reinforce the cold air that arrives at the end of this week with some potential for another round of light freezes early next week.

We talked about this yesterday, but it is worth revisiting. If Baton Rouge hits freezing on Friday morning, that would be early for the metro area but not something unusually rare. Records back to 1893 for the Red Stick indicate that roughly 1-in-3 autumn seasons record the first freeze on or before November 15th. However, since 1981 (33 autumns) there have only been five seasons with the first freeze occurring by November 15th: that’s a ratio of less than 1-in-6. Indeed, if we look at different periods over the past 100+ years for the Baton Rouge records, we get differing “average dates” for the first fall freeze for the Capital City:

Period Fall Freeze
1901-1930 Nov 28
1931-1960 Nov 20
1961-1990 Nov 26
1991-2013 Nov 26

Global warming? Climate change? Well, yes, even in Louisiana, the climate is always changing. This is also why we can call Thanksgiving Day as the rule-of-thumb date of the average first freeze, since the calendar date for Thanksgiving also changes, ranging from November 22nd to the 28th.

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