A blast of Arctic air will bring much colder conditions and possibly freezing rain/sleet as early as Thursday night into Saturday...
Johnson City ISD - Due to the high possibility of inclement weather in the hill country, Johnson City ISD is taking precautionary measures and will be starting school at 10:00 AM on Friday, December 6, 2013. Buses will run on a two hour delay.
South Central Texas Partners...Possible Freezing rain/sleet over portions of the area tonight into Friday...and again Friday night into Saturday.
...HEADLINE...Winter Weather Advisories are in effect for...Bandera, Bastrop, Blanco, Burnet, Caldwell, Comal, Edwards, Gillespie, Hays, Kendall, Kerr, Lee, Llano, Real, Travis, and Williamson Counties. These advisories are in effect from 8pm Thursday evening until 2 pm Friday.
...AREA OF CONCERN...Freezing rain/sleet possible along and north of U.S 90 (roughly from Del Rio to Schulenburg). Very cold temperatures will be affecting everybody in South Central Texas. This does include the Austin Metro area, but does not include the San Antonio Metro Area.
...IMPACTS...Average rainfall generally less than 1/4 inch through Friday night. Most of this will fall as cold rain tonight and early Friday, but some (maybe 0.10 inches) will fall as freezing rain/sleet over portions of the Hill Country tonight and maybe into the along the I-35 corridor by early Friday morning into the early afternoon hours. The main impact will be minor icing on bridges and other elevated surfaces, which could cause travel problems. Winter Weather Advisories are in effect for portions of South Central Texas (See headline above.) If heavier rain develops as some guidance indicates, the advisories may have to get upgraded to Winter Storm Warnings. The locations where this would be most likely would be the far western Hill Country through the northern I-35 corridor...including Llano, Burnet, and Williamson Counties. This is not definite but will be watched closely overnight. San Antonio should not see any impacts tonight as temperatures look like they will stay above the freezing mark.
...TIMING...A band of frozen precipitation stretches from the Big Bend of Texas through north Texas with ice accumulating in that swath. This area of precipitation is forecast to continue to push northeast and east and should impact our western most areas by late this evening....and then push into the I-35 corridor by the predawn/mornings hours early Friday. The threat time for icing will start out west by 8pm...icing may develop as early as 2-3 am in portions of the Travis/Williamson County. Elsewhere over the northern sections of South Central Texas, the chances of icing will be later Friday morning when temperatures finally drop below freezing.
...DISCUSSION...A strong cold front has pushed through all of South Central Texas with temperatures in the mid 30s to mid 40s over the Hill Country and I-35 corridor. Weak upper level disturbances will move across the area tonight and produce an area of mainly light rain. The rain will start to fall this evening west of I-35 and push across I-35 and areas east by Friday morning. The challenge of this event is when the temperatures will drop below freezing, and when they do, how much rain will still be falling. We think the temperatures will fall below freezing over the Hill Country late this evening with other areas north of San Marcos falling at or near freezing several hours past midnight. This will then lead to some icing concerns and thus we have issued Winter Weather Advisories for the counties listed above through 2 pm on Friday. Bridges and overpasses in the advisory areas will be the main concern.
Another possible icing impact may be Friday night into Saturday but confidence is lower on whether the precipitation will be heavy enough to cause any ice issues. It will definitely be cold enough for freezing rain/sleet across much of South Central Texas on Friday night/Saturday, but chances of rain are low and any precip that does fall should be light. We are however monitoring the situation in case other advisories/watches/warnings would be needed for later this weekend.
Any ice that is able to stick should do so mainly on bridges and overpasses, along with some trees and exposed surfaces. Crews need to monitor the roads closely. With light rain and drizzle in these overrunning situations, radar will be having a hard time picking up the echos any significant distance from the radar. So we need to rely on ground truth reports.
...SAFETY TIPS...Cold weather safety revolves around the four P(s): People...pets...plants...pipes. People and pets should stay indoors or be dressed appropriately when outside. Frostbite and hypothermia can result from extended exposure to the elements, both of which are serious and require immediate warming and medical attention. Plants should be brought indoors or covered.
We will update again on Friday morning. The latest forecasts and watches/warnings/advisories from the Austin-San Antonio National Weather Service are at www.weather.gov/austin