ICE THREAT Wed. into Thursday

FORECAST DISCUSSION:

Good Tuesday evening everybody. The low clouds, fog, mist and drizzle were never able to break up across a good portion of south central Texas today. Areas to the west of Austin and especially areas well southeast of Austin (La Grange, Giddings, and Houston among many others) were able to soar into the mid to upper 70s behind a warm front slowly creeping to the northwest. That warm, moist air advection (horizontal transport of air/moisture) is responsible for today’s widespread dense fog, mist and drizzle. Basically, the fog and mist are products of warm, Gulf air trying to compete with the lingering cool air mass over central Texas…the warm air is finally beginning to win as temperatures have now climbed into the upper 50s and lower 60s across a good portion of the Austin Metro Area. Warm advection continues through the night with temperatures actually expected to continue to rise a bit here in Austin. Low clouds, fog, mist and drizzle persist through the overnight hours into Wednesday morning with scattered light rain showers possible. A few sun breaks on Wednesday combined with continued warm air advection on southerly winds will allow for highs to top out in the upper 60s/lower 70s ahead of a powerful Arctic Front that will blow through the area somewhere between 2-6 p.m. Wednesday afternoon. The leading edge of that Arctic Air is just now beginning to move into the extreme northern Texas Panhandle. 

21Z (3 p.m. CST) Surface Analysis...leading edge of the Arctic Air just pushing into the extreme northern Texas Panhandle...image is courtesy of the Weather Prediction Center...and is available to you at anytime at this link: http://www.hpc.ncep.noaa.gov/sfc/namussfcwbg.gif

Rain/storms possible along and behind the front as it crosses the area tomorrow (Wednesday) afternoon. This is going to be one of those fronts where it drops from the 60s and 70s into the 30s and 40s within 20 minutes time. VERY WINDY conditions move in behind the front as the heavy, dense Arctic Air pours into the area. The National Weather Service has indicated that they may need to issue a WIND ADVISORY for portions of the area tomorrow afternoon. North winds sustained 20-25 mph will gust as high as 35-40 mph at times. Knowing that the Arctic Air is shallow and dense, it will force the warm, moist air up and over it aloft. Combine that moisture riding on top of the cold air with a series of disturbances moving overhead to provide lift and there is a concern for wintry precipitation across the area beginning early Wednesday evening and persisting I believe through midday Thursday. At this point in time, I’m concerned with the possibility of a freezing rain/sleet mix across a good portion of south central Texas, really from the Austin Metro Area and points north and west for possible ice accumulation on area roadways late Wednesday into early Thursday. Keep in mind that there may be school/work delays Thursday morning depending on how bad things get. How much wintry precipitation we are going to see? It’s not really for sure right now, however, we all know that it doesn’t take a lot around here to make a mess out of things. Given the nature of this weather setup (as it appears via the latest model information), freezing rain/sleet will be the biggest concern. However, a few snow flurries may be possible north and west of Austin Thursday morning where the cold air set-up will be more conducive for snow development. 

***In their latest forecast discussion, the National Weather Service stated that a WINTER WEATHER ADVISORY is likely to be issued by their next forecast update for much of south central Texas...a WINTER STORM WATCH/WARNING may be required for the the Hill Country based on future models' thinking about precipitation accumulation***

Here's their statement:

A WINTER WEATHER ADVISORY WILL LIKELY BE ISSUED IN THE NEXT
FORECAST PACKAGE...AND DEPENDING ON QPF TRENDS A WINTER STORM WATCH/WARNING MAY BE REQUIRED FOR THE HILL COUNTRY AND PORTIONS OF
CENTRAL TEXAS.

Great graphic from the National Weather Service Austin/San Antonio Forecast Office…issued just before 3 p.m. CST today:

-Areas shaded in pink and purple need to pay close attention to the forecast as icing looks to be a real threat (includes Austin Metro Area)

Forecast Precipitation Type across the area early Thursday morning according to the latest run of the GFS Model: