224
AWUS01 KWNH 282252
FFGMPD
TXZ000-290400-

Mesoscale Precipitation Discussion 0338
NWS Weather Prediction Center College Park MD
651 PM EDT Tue May 28 2024

Areas affected...Lower Pecos Valley...Southern Edwards Plateau
into South-central Texas...

Concerning...Heavy rainfall...Flash flooding possible

Valid 282250Z - 290400Z

SUMMARY...Strong thunderstorm cluster continues to grow with
increasing moisture flux from tongue of enhanced moisture coming
through the Rio Grande Valley.  Localized totals of 2-4" pose
possible flash flooding

DISCUSSION...GOES-E Visible and EIR depict a broad and strong
cluster with a few overshooting tops breaking through the
expanding canopy across the Lower Pecos River Valley.  Large
hail/severe signatures have dominated this cluster, but recent
trends note a slow transition toward higher rainfall production
(with continued more numerous hail stones, to help clog
culverts/drainage areas).

Recent surface analysis shows dry line continues to retrograde
under influence of enhanced eastward flow behind the outflow
boundary from this morning`s North to Southeast TX MCS. While this
has been more of a stabilizing influence a bit to the north in the
core of the cooler surface air;  gaps in the canopy continue to
show some low level cu from Kerr/Bandera county north of the
boundary, suggesting some of the higher theta-E air from the
western Gulf remains and supports moderately unstable air being
advected toward the complex.  Sfc to boundary layer inflow of
15-25kts with enhanced moisture nearing 1.75" PW through the
entire depth (though focused mainly in the lowest levels).  Also,
winds appear to be generally confluent to enhanced convergence to
support maintenance of the complex as it propagates southeastward.


So with ample unstable air and moisture being fluxed in and
cluster likely moistening the local environment; rainfall
efficiency will increase and likely reach sub-hourly rates of
1-2". WoFS members and HRRR 15-minute rates suggest 1-1.5" in
short duration.  Current orientation of the updrafts also suggest
potential for short-term repeating, especially as the upstream
flanking line will try to keep redeveloping with the retrograding
dry line.  As such, tracks of 2-4" of rainfall in 1-2 hours are
possible.  This brings the complex over lower FFG values of the
Lower Pecos River into Southern Edwards Plateau.

Confidence remains moderate to moderately-low; as Hi-Res CAMs have
continued to struggle. However, recent runs of the WoFS do suggest
means of 2-3" for the mean; while 90th percentiles are reaching at
or slightly above 4" especially near the Pecos River as the cells
remain slower moving/propagating in proximity to the dry line
retrograding.  So this adds some confidence to suggest flash
flooding remaining possible across the area of concern through 04z.

Also, of note, will be closely monitoring the complex over the
Serranias del Burro and trends as it emerges into South Texas.

Gallina

...Please see www.wpc.ncep.noaa.gov for graphic product...

ATTN...WFO...EWX...MAF...SJT...

ATTN...RFC...WGRFC...NWC...

LAT...LON   31040126 30820010 30309866 29599828 29079874
            29089995 29750118 30030191 30090214 30490255
            30960207