MD 0648 CONCERNING SEVERE POTENTIAL…WATCH LIKELY FOR PORTIONS OF SOUTH-CENTRAL TEXAS
Mesoscale Discussion 0648
NWS Storm Prediction Center Norman OK
0152 PM CDT Fri Apr 28 2023
Areas affected...portions of south-central Texas
Concerning...Severe potential...Watch likely
Valid 281852Z - 282015Z
Probability of Watch Issuance...95 percent
SUMMARY...The severe threat is expected to increase as storms
initiate ahead of a merging cold front/dryline over the next few
hours. Hurricane-force wind gusts and very large hail over baseball
size is possible with the strongest storms. A WW will be needed
soon.
DISCUSSION...A dryline continues to meander eastward across the TX
Hill Country as a cold front drifts southward over the TX Big
Country. These boundaries are expected to merge over the next few
hours, increasing low-level convergence within a well-mixed, very
buoyant boundary layer. Current observations show surface
temperatures/dewpoints exceeding 80/upper 60s F ahead of the
dryline, that combined with 8+ C/km 700-500 mb lapse rates (per 18Z
mesoanalysis) are contributing to over 2500 J/kg MLCAPE.
Furthermore, regional VADs are showing substantial veering with
height in the 850-500 mb layer, resulting in 40 kts of effective
bulk shear. As storms initiate ahead of the merging fronts,
supercell modes should result, supporting the threat for large hail
(including a few instances of 3+ inch stones possible). The strong
convergence along the merging fronts will also support storm/cold
pool mergers, which will promote a severe wind threat. Given the
well-mixed boundary-layer preceding very intense storm cores,
evaporative cooling may become strong/efficient enough to support
65+ kt gusts). A WW will be needed soon to address the increasing
severe potential.
..Squitieri/Thompson.. 04/28/2023
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...FWD...CRP...EWX...SJT...
LAT...LON 29010083 30249988 30669931 30849877 30939824 30789728
30239716 29039808 28259917 27960007 28120023 29010083
