SUMMARY...Slow moving heavy thunderstorms generally shift
southwest through the Rio Grande rest of this morning.
Considerable flash flooding continues with rainfall rates of
2-3"/hr.
DISCUSSION...As of 13Z, a low level trough axis positioned east of
the Big Bend extends northeast through Del Rio to the TX Hill
Country. MCVs have developed in the activity including over Uvalde
and Sutton Counties. Instability west of these MCVs and into the
trough has focused new development west of existing activity
toward the Rio Grande. MLCAPE is around 1500 J/kg west of the
current activity along the Rio Grande. This is on the western end
of an impressive swath of PW over Texas with 1.8" through the
Stockton Plateau and 2.2" south from Del Rio. The whole pattern
over this area continues to shift west under the closed high
centered over southern MN. This further encourages westward
movement to the activity this morning.
Areas farther west that had the extreme rainfall overnight are
currently under stratiform rain. An exception is the MCV over
Uvalde Co has not moved in awhile as new development has shifted
to the west side of the MCV. There is plenty of activity west of
this MCS northeast of San Antonio which will be a focus area for a
separate discussion.
Recent HRRR and RRFS runs have underdone this western extent of
activity, especially the narrow swath of heavy rain over the
Trans-Pecos and Stockton Plateau. This area south through the bend
east of the Big Bend is included in the discussion given the
sufficient moisture and instability present for heavy rain. Areas
south of Uvalde are also included despite RRFS/HRRR keeping heavy
rain generally north of the city of Uvalde also given the
ingredients of moisture, instability, and convergent forcing.