Subj : MESO: Heavy rain - floodi
To   : All
From : Mike Powell
Date : Sun Apr 23 2023 09:08:00

AWUS01 KWNH 231023
FFGMPD
TXZ000-231600-

Mesoscale Precipitation Discussion 0205
NWS Weather Prediction Center College Park MD
623 AM EDT Sun Apr 23 2023

Areas affected...portions of southern TX

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

Valid 231021Z - 231600Z

Summary...A localized risk of flash flooding will continue for
portions of southern TX through 16Z. Peak rainfall rates of 2-4
in/hr and additional totals of 3-5 inches will be possible.

Discussion...10.3 micron satellite imagery at 10Z showed an MCS
continuing to organize near and east of Del Rio, TX. Several
supercells were noted in the vicinity of a southward sinking cold
front but they have been merging and congealing over the past 1-2
hours on either side of the Rio Grande, resulting in a
southeastward movement to the convective cluster. Downstream
instability remained supportive of convective maintenance over the
next few hours with 1000-2000 J/kg MUCAPE observed from the Middle
Rio Grande Valley to the middle/lower TX Coast via the 09Z SPC
mesoanalysis. In addition, surface observations showed the western
extension of a stationary front, marked by low to mid-70s
dewpoints to its south and dewpoints in the lower to upper 60s to
its north extending from the western Gulf of Mexico across the
lower TX Coast.

Forecast Corfidi vectors show the MCS should continue advancing
southeastward toward the lower/middle TX Coast over the next 6
hours with training of heavy rain generated by repeating and/or
merging cells along its southern/southeastern flank. In addition,
as cooler temperatures near 700 mb sink southward this morning,
erosion of a warm layer noted on the 00Z CRP sounding may support
the development of overrunning convection along the Coastal Plain,
eventually merging with the advancing MCS from the northwest. The
combination of these forecast scenarios will likely support
occasional rain rates of 2 to perhaps as much as 4 in/hr. While
the MCS is expected to become increasingly forward propagating
over the next few hours, a localized flash flood threat will
continue across south-central TX with 3 to perhaps 5 inches of
additional rainfall.

Otto

ATTN...WFO...BRO...CRP...EWX...

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

LAT...LON   29709891 29199774 28409643 28029667 27829682 
            27509701 27229714 27159764 27149889 27529979 
            28200046 29070086 29350017 

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