AWUS01 KWNH 210659

FFGMPD

LAZ000-TXZ000-211255-



Mesoscale Precipitation Discussion 0487

NWS Weather Prediction Center College Park MD

257 AM EDT Sun Jun 21 2026



Areas affected...middle and upper TX coast into southwestern LA



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



Valid 210656Z - 211255Z



SUMMARY...Increasing thunderstorm coverage is expected across the

middle and upper TX coast into southwestern LA through 13Z. Peak

hourly rainfall over 2 inches is expected along with possible

flash flooding.



DISCUSSION...Radar imagery in the vicinity of Corpus Christi Bay

at 0630Z showed scattered thunderstorms. These storms may have

formed in response to outflow advancing outward from an earlier

cluster of thunderstorms which collapsed ~100 miles off of the

lower TX coast shortly after 01Z. Regardless of the reason for

initiation, the entire Coastal Plain of TX has been seeing a

return to an unstable environment after Saturday afternoon's

convection stabilized a good portion of central TX to the Coastal

Plain. Trends over the past 4 hours in MLCAPE from the SPC

mesoanalysis showed this well as low level onshore flow of 15-25

kt has been helping to advect low level moisture (and instability)

back inland, Meanwhile, a mid-level low remained over

south-central TX (~80 miles south of San Antonio) on infrared

satellite and low level water imagery, with a shear axis extending

along the TX coast into western LA.



Additional outflow potentially propagating northward from the

western Gulf and low level convergence on the nose of a subtle

uptick in low level flow is expected to initiate thunderstorms

along the upper TX coast into southwestern LA over the next 1-2

hours. The onshore low level flow may act to support brief

upstream redevelopment and training of heavy rain with the deeper

layer mean steering flow from the S to SW at 10-20 kt. Hourly

rainfall of 1 to 3 inches will be possible, but values above 2

inches should remain isolated to widely scattered in coverage. The

increasing coverage of thunderstorms will result in a possible

flash flood threat from near Corpus Christi Bay to the upper TX

coast and into southwestern LA. Storm total rainfall of 2 to 4

inches is expected (locally higher possible) through 13Z atop a

good portion of the Gulf Coast that has received 300 to 600+

percent of average rainfall over the past week, lessening soil

absorption capabilities.



Otto



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



ATTN...WFO...CRP...EWX...HGX...LCH...



ATTN...RFC...FWR...ORN...NWC...



LAT...LON   30759387 30719294 30359195 29789204 29429271 

            29529399 28669514 28299584 27899647 27809717 

            28019772 28609777 29429698 30049615 30559497