Monday, December 22, 2014

Strong to Severe Storms Possible on Tuesday

By Jay Grymes & Steve Caparotta

WAFB First Alert Quickcast:
- potential for another round of area fog tonight and early tomorrow
- “marginal” threat for severe weather this evening into early Tuesday
- “slight risk” for severe storms on Tuesday, especially from mid-day into the early evening

The next 24 hours could be rather busy for some residents of the central Gulf Coast as a variety of weather features combine for a potentially stormy Tuesday. The trade-off is that by early Wednesday the weather takes a turn to the “good” and delivers a back-to-back cooperative winter days for Christmas Eve and Christmas Day.

Yes .. we said winter, as Sunday was the Winter Solstice, making today the first ‘full’ day of winter. However, today certainly didn’t have much of a winter feel with highs in the 70°s. A mild and moist air mass over our region promoted fog development earlier today, and the same set-up means another round of fog possible for Tuesday’s start -- if the winds subside enough. At the same time, a warm front moved northward out of the Gulf today and is headed well to our north. The Gulf air behind the warm front will add even more moisture (dew points at 60° or more) to the lower levels which will increase low-level instability. 

We’ve seen a few passing showers today and we’ll keep isolated rains in the evening and late night forecasts too. 

At the upper levels, a deepening trough and southwesterly flow over the central Gulf Coast will work with the moist and unstable air mass, providing lift that could be sufficient to generate a few storms from this later this evening into the early morning. That’s why the NWS Storm Prediction Center (SPC) has just about the entire central Gulf Coast under a “marginal” risk for severe weather through tonight. The set-up isn’t the best for active-to-severe storms, but the SPC sees that enough is in place for one or two strong-to-severe storms to possibly develop somewhere along the Gulf Coast rim. (Remember, “marginal” means that chances are 5% of a severe storm developing within 25 miles of any location -- that’s very low but not a “zero” chance.)

The greater threat for active weather arrives during the day on Tuesday as an approaching cold front provides an even better lifting mechanism to take advantage of the region’s unstable air mass. We’ve got rain chances through the day on Tuesday at 80% or better - - let’s face it, just about everyone gets wet. It won’t be an all-day rain, but we can expect periods of showers and occasional t-storms starting in the morning hours and extending through the afternoon. We’ve got the front moving into the WAFB viewing area from the west sometime close to the evening “dinner hours” and we’ll be on the watch for a developing squall line of storms ahead of the main cold front. 

The severe threat will be mainly in the form of damaging winds although a few tornadoes cannot be excluded. Large hail is also a possibility with the larger thunderstorms. For the WAFB area, the severe threat should end from west to east during the late evening hours on Tuesday, depending on the forward speed of the front.

Once the front passes, the weather will begin to improve, albeit somewhat slowly. It looks like we could still be under a mostly cloudy sky for Wednesday’s sunrise, but the clouds should slowly clear throughout the day. By Wednesday night into Christmas morning, we’re expecting mainly clear skies with a light freeze possible for WAFB’s northern and eastern communities. Christmas day should be mainly sunny but cool, with highs in the 50°s.

We’ll bring a slight chance of showers to the forecast for Friday with scattered showers and a few thunderstorms possible on Saturday. That should clear things out for a nice Sunday.

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