Update on Thunderstorm Trends for the Midday and Afternoon Hours Today...

Expected impacts:

• Scattered showers and isolated thunderstorms are possible through 2pm
• Showers and thunderstorms are expected to become more numerous toward/after 2pm, on into the early to mid-evening hours
• Locally heavy rainfall is likely at times with thunderstorms especially later this afternoon into early this evening, which could produce flooding at times in low lying and poor drainage areas
• Storm total rainfall of 2-3 inches is expected across most of the area, with localized amounts of 3-4 inches possible in some spots
• A few strong to severe thunderstorms could also produce strong, gusty winds and/or hail in at least some parts of the area later this afternoon into early this evening

Discussion:
...Near Term Update and Forecast...
The shower and thunderstorm activity that moved through the area this morning continues to shift off to the South and East of the area at this time, and has formed into a solid line from near San Antonio to Seguin to Bastrop. This activity has effectively cut-off the flow of moisture into the area from the Southeast, and has, at least temporarily, resulted in a significant stabilization of the local atmosphere (note the cool, North breeze across the area at this time).

The above mentioned boundary now to the South of us, called an outflow boundary, is expected to stall soon as Southerly winds increase in Deep South Texas. One of two things will then happen this afternoon: 1). The boundary will hold nearly stationary to the South of the area through the afternoon, thereby keeping the highest risk of strong to severe thunderstorm activity to the South of the local area where the air is more unstable or 2). the boundary could start lifting back Northward and reach at least some portions of the local area later this afternoon. If scenario 2 were to occur, it would most likely be into southern portions of the area (i.e., Hays County), with decreasing probability as you move Northward.

If scenario 2 occurs, then there will be a risk of strong to severe thunderstorm activity, with hail and/or strong, possibly damaging wind gusts in the affected areas, as well as very heavy downpours of rain and of course, lightning. This would occur mainly from toward/after 2-3pm through about 7-8pm. If scenario 1 occurs, then we can expect scattered to numerous showers and scattered thunderstorms, some of which could produce small hail in some parts of the area, as well as locally heavy downpours of rain, this afternoon into early this evening.

Regardless as to which of the above scenarios takes place, all shower and thunderstorm activity should move East out of the area by around 8-9pm this evening, based on present trends.

We will continue monitoring the progress and/or return of the outflow boundary during the midday and afternoon hours and issue additional updates as trends become identified.

...Expected Rainfall and Possible Low Land Flood Risk...
Regardless as to which of the above scenarios takes place, locally heavy downpours of rain will be likely again at times in many parts of the area during the afternoon (especially toward/after 2-3pm) into the early evening hours. Heavy rain will be more widespread if scenario 2 occurs, and less widespread (more scattered to regional in nature) if scenario 1 occurs.

Any periods of heavy rainfall this afternoon into early this evening may result in mostly minor flooding of low lying and poor drainage areas, such as low water crossings and similar areas. If scenario 2 above occurs, and the heavier rain is more widespread, runoff may continue well into the late evening and overnight hours, well after the falling rain has ended, in the affected areas.

We will continue monitoring the situation and issue updates and/or specific alerts/warnings as conditions warrant.