Mesoscale Discussion 0469
NWS Storm Prediction Center Norman OK
0806 AM CDT Sat May 01 2021
Areas affected...Rio Grande Valley eastward into southern Texas
Concerning...Severe potential...Watch unlikely=20
Valid 011306Z - 011500Z
Probability of Watch Issuance...20 percent
SUMMARY...Storms crossing the Rio Grande may produce marginal hail
this morning, but a watch is unlikely.
DISCUSSION...Storms have increased in intensity and coverage over
northern Coahuila, with marginal MESH shown on radar. These storms
are in a rather weakly unstable air mass with only a few hundred
J/kg of MUCAPE, but are aided by cooling aloft with the upper low.
The 12Z DRT sounding shows little instability, but modifying for
observed temperatures and dewpoints to the southeast yields
Ample PWAT exists over southern TX (1.50-1.75" per GPS sensors), but
little heating is expected in the near term. However, easterly mean
winds in the low levels will aid storm-relative inflow to any
approaching cells, and may maximize updrafts despite marginal
instability. Cold temperatures aloft could support hail.
Storm evolution will continue to be monitored this morning as
conditions ahead of these storms destabilize further.
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