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Flash Flood Guidance
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000
AWUS01 KWNH 250311
FFGMPD
TXZ000-250800-

Mesoscale Precipitation Discussion 0491...Corrected
NWS Weather Prediction Center College Park MD
1110 PM EDT Mon Jun 24 2019

Corrected for additional text in the last paragraph

Areas affected...South Texas

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

Valid 250304Z - 250800Z

Summary...Localized very heavy rain will continue to affect far
southern Texas over the next 3-5 hours. Rainfall rates over 3
in/hr at times will be possible, leading to additional rainfall of
4-8 inches through 08Z.

Discussion...Extremely heavy rain continues to affect a small
section of South Texas with KBRO radar derived estimates of 3-7
inches along the borders of Hidalgo, Willacy and Cameron Counties
with at least one Wunderground.com report showing 5 inches in 2
hours near Elsa ending 02Z. An MCV was observed in base velocity
imagery drifting south from western Willacy into western Cameron
Counties, with some slowing and possible weakening over the past
30 minutes (ending 0230Z). However, GOES East clean window IR
cloud top temperatures continue to show -75 to -80C despite some
recent warming along the Rio Grande. The 00Z sounding from BRO
showed a wet bulb zero height of 14.4 kft with MLCAPE of 4200 J/kg
and a precipitable water value of 2.5 inches.

Radar reflectivity implies outflow over northern Tamaulipas moving
ESE which may coincide with an eventual eastward drift to the MCV
over western Cameron County. 30 kt of southeasterly flow at 850 mb
will continue to focus the best influx of low level
moisture/replenishment into Willacy and Cameron Counties over the
next few hours with rainfall rates over 3 in/hr at times with
additional storm total of 4-8 inches expected given the slow
movement of the MCV which is serving as the focus for the heaviest
rainfall rates in the presence of diffluent flow aloft. This will
result in a focused area for extremely heavy rain and dangerous
flash flooding, affecting the city of Harlingen and perhaps
Brownsville.

Otto

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

ATTN...WFO...BRO...

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

LAT...LON   27129758 26799681 26229661 25689690 25499746
            25529815 26139861 26909827

National Weather Service Weather Forecast Office