497
AWUS01 KWNH 200113
FFGMPD
TXZ000-200601-

Mesoscale Precipitation Discussion 0470
NWS Weather Prediction Center College Park MD
912 PM EDT Wed Jun 19 2024

Areas affected...South Texas

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

Valid 200111Z - 200601Z

Summary...Convective rainbands along the outer periphery of
Tropical Storm Alberto continue to stream into South Texas.
Rainfall amounts of 2-5" could lead to some instances of flash
flooding through 6z.

Discussion...Radar continues to track several bands of tropical
convection entering South Texas as Tropical Storm Alberto
continues a westward track into northeast Mexico. Recent banded
convection close to the Texas coastline exhibited cooling cloud
tops accompanied by an uptick in radar estimated rain rates to
1.5-2"/hr per MRMS and KCRP. This confined area of enhanced
convection likely remains tied to an inverted trough along the
coastline, with plenty of low-level convergence and 2000 J/kg of
MLCAPE within a tall and skinny profile (NCAPE around .1).
Moreover, effective SRH upwards of 200 m2/s2 will support shallow
supercell structures to dynamically enhance rainfall rates (see
SPC MD 1336 for more on the severe weather threat), with 2.6-2.7"
PWATS noted in the inflow region of these cells.

Over the next several hours, the inverted trough is expected to
migrate inland, advecting 1000-1500 J/kg MLCAPE across South
Texas. This will allow for the more efficient bands containing
2-2.5"/hour rainfall rates to move across South Texas. Where the
most organized bands persist, rainfall of 2-5" could fall through
6z. Generally, the overall impacts with this activity will likely
depend on if any bands can train over areas which saw heavy
rainfall earlier today along the coastline, where 5-9" of rainfall
is estimated over the last 12 hours. Further inland across South
Texas, some flash flood issues also remain possible through 6z, as
the HREF suggests an appreciable (30-40%) chance of 10 year ARI
exceedence, with some signal (10-15%) for 100 year ARI exceedences
also noted.

Asherman

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

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

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

LAT...LON   28839698 28659664 28229656 27369721 26679722
            26019712 25799736 25909811 26269896 26659928
            27119958 27639992 28099981 28369892 28679782