Friday, December 5, 2014

Waiting on the Weekend Cool Front

By Jay Grymes & Steve Caparotta

WAFB First Alert Quickcast:
- another round of morning fog for Saturday
- cool front arrives Saturday afternoon/evening

The fog this morning didn’t get quite as dense or widespread as we had feared: great news for the Friday morning commute. But you likely noticed the warmth today -- in fact, today’s high clipped the 80°s for some neighborhoods. For Metro Airport (BTR), today was the third 80°+ over the last six days. Today’s 82° is the warmest of the lot, and just 2° shy of the daily record, which happened to be set last year.

So with this warmth (and humidity), lots of people are looking for a change to something a bit more normal, if not downright wintry. We’ve got a weak cool front sliding through the Bayou State on Saturday: that will bring a modest rain chance to the region through the day and also deliver a cooler and less-humid air mass over the weekend.

But before the “cool down,” we’ve got to get through Saturday. As we’ve seen for the past several mornings, fog will once again be a concern for the overnight and early morning hours. As of 3:30pm, the NWS Office in Lake Charles (NWS/LCH) had already posted a DENSE FOG ADVISORY (DFA) for areas along and west of the Atchafalaya Basin. The NWS/LCH DFA will be in effect from midnight until 10:00am on Saturday.

The NWS Office in Slidell (NWS/LIX) has yet to follow suit with a DFA for their service region as of 4:00pm. They still may issue one later this evening, but for now they are anticipating that the winds and cloud deck will inhibit the formation of widespread dense fog on the east side of the Atchafalaya Basin as well as around metro Baton Rouge and the tidal lakes. We aren’t entirely convinced, as just about all the key factors appear to favor another round of fog tonight and early Saturday, with areas of dense fog (visibility under ¼-mile) likely. However, given that this morning’s fog failed to achieve DFA criteria (even though conditions appeared favorable), we understand the hesitance by NWS/LIX. In either case, if you are planning some late night or early morning travel, be prepared to encounter some dense fog pockets, especially in and around those “usual suspect” locations.

We’ll also toss in some rain chances for Saturday as the weak cool front slides from NW-to-SE across the state. We’re going with spotty-to-isolated rains (less than 20%) for the early to mid morning then raising those chances to around 30% from the late morning into the afternoon. With these limited percentages, it is evident that most stay dry tomorrow. What’s more, even if it does rain over your backyard it won’t amount to much: we’re expecting most rain reports to come in at under one-tenth of an inch.

By Saturday evening, the front should be moving towards the coastal waters, the winds will have already come around earlier in the day, and cooler-and-drier air will be filtering into the region. We’ll call for partly cloudy skies for Saturday night into Sunday morning with no fog threat for Sunday and morning lows down in the 40°s for the northern half of the WAFB viewing area. Skies will continue to slowly clear through the day on Sunday, with an afternoon high in the mid to upper 60°s.

Our extended outlook is a dry one through next Friday under fair to partly-cloudy skies, with daytime highs all week long in the 60°s -- at or slightly below the seasonal norms. Morning starts will be in the 40°s on most days, although a secondary surge of cool, dry Canadian air near mid-week could result in the 30°s for some WAFB communities, but we don’t see anything close to a freeze based on the current guidance.

Enjoy your weekend!

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