The following weather advisory came in today from the National Weather Service in Brownsville.
By now, you may have been alerted to the potential for afternoon thunderstorms capable of producing damaging wind gusts and large hail. While there is such potential, confidence in a widespread event occurring Valley-wide is Low. Here are a few details as to why.
Dry air. The atmosphere is notably drier today than it was on March 29th and April 16th. It's difficult for relatively warm/humid 'bubbles' of air to survive en mass rising into this drier atmosphere which tends to evaporate them - if the "Cap" is broken.
Capping. "Capping" is a term we use when a warmer layer of air exists over cooler air below it. A cap will suppress the development of thunderstorms, which need the ability of the relatively cooler air to rise at all. Caps also allow a buildup of energy below them, which, if the cap "breaks", allow for explosive thunderstorm growth. Today's cap may hold, or may break - barely - in time to allow thunderstorms to grow. Problem then becomes...dry air above it (see bullet point #1).
Disruptive Energy. Leftover boundaries from last night's thunderstorms that moved through Coahuila State into the Big Bend region before dissipating have aided some shower and isolated storm development this morning. This activity is already moving into Webb and even Zapata County and may reach the Valley (if it holds together) between noon and 2 PM. Problem is, cap will still be in place, and atmosphere is dry enough to preclude rapid development so soon. This "wave" would also shift winds to north and re-establish a cap for a couple of hours during what would normally be peak heating time (2 to 4 PM), and not allow the atmosphere to "re-set" in time to develop widespread thunderstorms with wind and hail.
Bottom Line: We can't rule out a "rogue" storm that could produce winds in excess of 60 mph and hail the size of quarters or larger for a brief period. But, we have little confidence on a more widespread outbreak of damaging wind and large hail storms this afternoon. In fact, one of our more reliable very short range models indicates the better chance along the Coastal Bend, mainly north of Corpus, with the tail of the activity "drying up" before reaching the Valley.
Storms of significance, should they develop, would arrive between 3 and 6 PM; the threat passes by or before sunset for the Valley.blog comments powered by Disqus