Graphic for MPD #0031

Mesoscale Precipitation Discussion 0031
NWS Weather Prediction Center College Park MD
1227 AM EST Thu Jan 25 2024

Areas affected...southeastern TX into south-central LA and
southwestern MS

Concerning...Heavy rainfall...Flash flooding likely

Valid 250525Z - 251015Z

SUMMARY...Another round of heavy rain is expected to impact
portions of the southeastern TX Coastal Plain into central LA and
southwestern MS over the next few hours. Peak rainfall rates of
0.5 to 1.5+ in/hr and additional totals up to 3 inches are
expected prior through 10Z. Areas of flash flooding are considered
likely due to wet antecedent conditions.

DISCUSSION...05Z GOES East infrared imagery showed two areas of
colder cloud tops associated with higher intensity rainfall at the
surface. Radar imagery showed the first area over the lower Sabine
River Valley into central LA and the second area near and east of
San Antonio, TX. The eastern area was partially tied to an
increase in the 850 mb wind as sampled by the KHGX VAD wind with a
~10 kt increase in magnitude over the past hour. The western area
was located ahead of a mid to upper level shortwave located over
southern portions of the Pecos River Valley, tracking east on
water vapor imagery.

Instability via the 05Z SPC mesoanalysis was decreasing along the
I-37 corridor south of San Antonio and MUCAPE was roughly 500-1000
J/kg along the middle TX coast and south-central LA/MS. However,
as the shortwave trough axis continues to move east tonight,
continued strengthening of the low level flow into the upper TX
coast and Lower Mississippi Valley is forecast by the RAP with
expanding 20-40 kt coverage through 10Z. The resultant increase in
850-700 mb moisture will increase 700-500 mb lapse rates and
elevated instability for coastal regions of southeastern TX as
well as into portions of LA and MS. The MUCAPE gradient is
forecast to align from SW to NE, quasi-parallel to deeper layer
steering flow from the southwest, supporting the potential for
periods of repeating and training of heavy rain. As the shortwave
edges eastward, increasing forcing and upper level divergence to
the southeast of a 110-120 kt upper level jet combined with the
increasing instability should allow for an expansion of heavy
rainfall coverage and intensity over the southeastern TX Coastal
Plain. Both in TX and the Lower Mississippi Valley, peak rainfall
rates in the 0.5 to 1.5+ in/hr range will fall on areas of
saturated ground due to heavy rainfall over the past 24-72 hours.
While probably not widespread in coverage, areas of renewed flash
flooding are considered likely given the forecast for an
additional 1 to 3 inches of rainfall atop the sensitive ground
conditions.

Otto

ATTN...WFO...CRP...EWX...HGX...JAN...LCH...LIX...SHV...

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

LAT...LON   32499091 32459034 31968996 31259076 30039189
            29489396 28679589 28539730 28839796 29299772
            30249630 31589430 32039240
Download in GIS format:    Shapefile  | KML



Last Updated: 1227 AM EST Thu Jan 25 2024