MD 0654 CONCERNING SEVERE POTENTIAL…SEVERE THUNDERSTORM WATCH LIKELY FOR SOUTH TEXAS
Mesoscale Discussion 0654
NWS Storm Prediction Center Norman OK
0534 PM CDT Fri Apr 28 2023
Areas affected...South Texas
Concerning...Severe potential...Severe Thunderstorm Watch likely
Valid 282234Z - 290030Z
Probability of Watch Issuance...80 percent
SUMMARY...Thunderstorms developing off the terrain in Mexico may
migrate east of the Rio Grande this evening. If so, storm
intensification is probable. A more robust severe threat is likely
as storms migrate south/southeast along the Rio Grande. Watch
issuance is expected to address this concern.
DISCUSSION...Recent regional radar mosaics and GOES visible imagery
show robust convection maturing over the terrain of north/northeast
Mexico. This activity is largely being driven by orographic ascent,
but mean westerly flow will likely result in gradual movement
towards the Rio Grande over the next couple of hours. Both left and
right supercell deviant motion is noted in some of these cells,
suggesting that the timing of when they may cross the international
border is uncertain. Additionally, storm longevity is uncertain due
to storm interactions between the splits and/or loss of forcing for
ascent away from the terrain. This idea is reflected in recent
hi-res guidance, which also depicts a spread in when/if this
crossover occurs. However, if cells can migrate into the U.S. they
will encounter a buoyancy-rich environment with MLCAPE values on the
order of 3000 J/kg, which will support intensification.
To this north of this activity, a pair of organized, but undercut,
supercells are migrating to the east/southeast roughly parallel to
the Rio Grande. The combination of strong forcing for ascent along
the cold front and a downstream reservoir of very high buoyancy
yields high confidence that organized convection with an attendant
hail/wind threat will persist downstream. Watch issuance will be
needed to address this threat.
..Moore/Grams.. 04/28/2023
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...CRP...EWX...BRO...
LAT...LON 26449911 27189945 27539951 28010002 28449968 28739867
28509830 28049819 27089824 26679831 26439844 26269865
26369886 26449911
