At midday, a warm front at the surface was moving Northward along the middle Texas coast and Rio Grande Valley (see red line on surface map above). To the South of the front, a moist and increasingly unstable airmass is flowing Northward. Dew points in the 60s have advanced as far North as a line from near San Antonio to near Houston as of this hour, and will continue surging Northward during the afternoon and evening hours.
Thunderstorms are increasing in coverage and somewhat in intensity along and to the immediate North of the warm front at this hour, generally between Austin and Houston:
Some of the stronger storms over central and east Texas may begin to produce hail to severe limits (i.e., 1 inch in diameter) during the next few hours. A storm that passed through the Austin area earlier produced hail the size of small marbles. Very heavy downpours of rain and dangerous lightning can also be expected with this activity this afternoon.
There is also a slight chance of an isolated tornado or two with any storm that forms right along or immediately North of the warm front this afternoon, due to the favorable turning of wind direction with height in that area. A widespread tornado threat is not anticipated this afternoon in central or east Texas.
Meanwhile, further West, a strong upper level storm system was moving toward West Texas at midday:
This system is expected to interact with the moisture surging in from the Gulf and result in rapid thunderstorm development near a surface trough of low pressure across West Texas and/or the Big Bend region by mid-evening. Tornadoes, large hail and damaging winds will all be possible with this activity.
Once developed, the activity over West Texas is expected to congeal into a line and/or one or more clusters of severe thunderstorms and move East toward the I-35 corridor (including the Austin-San Antonio Metro areas) after Midnight. Damaging straight line wind gusts and large hail will be the primary threats by that time, however isolated tornado development cannot be ruled out. The activity will likely then progress into the coastal Plains by dawn on Wednesday.
With the above in mind, the latest severe weather outlook from the SPC in Norman, OK is shown below. The severe weather threat is primarily confined to the yellow shaded areas on the image:
Folks living in and near the severe weather threat area in Texas should remain alert this afternoon into the evening and overnight hours. Review severe weather safety tips now, and have a safe shelter in mind should severe weather threaten your area later. Be sure that you have a NOAA Weather Radio with a battery back up or another means of obtaining warnings should severe weather threaten when you are sleeping tonight.
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