Severe storms possible Monday night into Tuesday
Forecasts continue to show threats for both severe storms and flash flooding through Tuesday morning. A few severe storms may affect the Rio Grande area late today, but the more widespread threat for storms and flooding will affect all of South Central Texas Monday evening through Tuesday morning. A Flash Flood watch has been issued for much of the area from 6 pm Monday until Noon on Tuesday.
A large upper storm system, along with a cold front, will push through the area Monday night and Tuesday. Ahead of this system, a disturbance may cause a few strong to severe thunderstorms to form over Mexico and move across the Rio Grande and affect areas mainly west of a Mountain Home to Eagle Pass Line late today and tonight. Damaging hail and wind are possible.
More focused attention is being placed on the Monday evening-Tuesday morning time frame when the large upper low and associated cold front moves through South Central Texas. Severe thunderstorms will likely form over the Edwards plateau and Hill Country Monday afternoon and evening. Damaging wind and large hail will be the primary threat. Tornadoes cant be ruled out. As the system moves east Monday night and early Tuesday, thunderstorms will become widespread (possibly a large line of storms) and move across all of South Central Texas overnight.
While the timeline is still evolving, models are consistent that the main threat time across the I-35 corridor will probably be between 2 AM and 8 AM Tuesday morning. Areas to the west in the Hill Country will see impacts as early as Monday evening....and areas to the east of I-35 may see impacts past the 8 am hour on Tuesday. It does look like the rush hour for Tuesday morning will be impacted.
The upper low is forecast to move rather slow, increasing the threat for heavy rains mainly east of a Castell to Pearsall line. 1-3 inches of rain is expected with isolated totals of 4-6 inches. Farther out west... totals generally less than 2 inches are expected. A Flash Flood Watch is in effect from 6 pm Monday through Noon on Tuesday for the following counties of South Central Texas: ATASCOSA...BANDERA...BASTROP...BEXAR...BLANCO...BURNET...CALDWELL...COMAL... DEWITT...FAYETTE...FRIO...GILLESPIE...GONZALES...GUADALUPE...HAYS...KARNES... KENDALL...KERR...LAVACA...LEE...LLANO...MEDINA...TRAVIS...WILLIAMSON...WILSON.
Rain chances, severe threat, flash flood threat should diminish by late Tuesday morning. Depending on rainfall however, river and creek flooding may continue well beyond Tuesday morning.
National Weather Service Austin-San Antonio TX