608
AWUS01 KWNH 210350
FFGMPD
GAZ000-TNZ000-ALZ000-210949-
MESOSCALE PRECIPITATION DISCUSSION 1101
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1149 PM EDT THU AUG 20 2026
AREAS AFFECTED...PORTIONS OF NORTHERN ALABAMA INTO NORTHERN
GEORGIA
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE
VALID 210349Z - 210949Z
SUMMARY...ISOLATED FLASH FLOOD POTENTIAL EXISTS WITH A RECENTLY
DEVELOPED CLUSTER OF CONVECTION NEAR THE HUNTSVILLE AREA. THIS
CONVECTION WILL SLOWLY MIGRATE EASTWARD WHILE PRODUCING AREAS OF
1-1.75 INCH/HR RAIN RATES.
DISCUSSION...DEEP CONVECTION HAS INCREASED IN COVERAGE AND BEGAN
TO CONGEAL INTO A CLUSTER NEAR THE HUNTSVILLE, AL AREA OVER THE
PAST HOUR. THE STORMS HAVE FORMED NEAR A COLD FRONT ALONG THE
TN/AL BORDER AND WERE BEING SUPPORTED BY WEAK ASCENT ASSOCIATED
WITH A MID-LEVEL WAVE OVER MIDDLE TENNESSEE AND A VERY
MOIST/UNSTABLE AIRMASS ALONG AND AHEAD OF THE FRONT (2+ INCH PW,
3000+ J/KG MLCAPE), SUPPORTING EFFICIENT RAINFALL PROCESSES
BENEATH THE STORMS. FURTHERMORE, THE STORMS WERE IN AN
ENVIRONMENT CHARACTERIZED BY WEAK STEERING FLOW ALOFT (10-20 KNOTS
ON AVERAGE), SUPPORTING SLOW STORM MOTIONS. THE CONVECTIVE
CLUSTER WAS EXHIBITING SIGNS OF CONGEALING OVER THE PAST 30
MINUTES OR SO, WITH MULTIPLE MERGERS AND SLOW CELL MOVEMENT
FOSTERING AREAS OF 1.5+ INCH/HR RAIN RATES.
OVER TIME, THE CONGEALING OF THIS CONVECTIVE CLUSTER SHOULD RESULT
IN GRADUAL EAST/SOUTHEASTWARD PROPAGATION TOWARD NORTHERN GEORGIA.
DOWNSTREAM AREAS CONTAIN FFG THRESHOLDS OF AROUND 1.5-2 INCH/HR,
WHICH COULD BE EXCEEDED AT TIMES GIVEN THE FAVORABLE AIRMASS AND
SLOW CELL MOVEMENT. DOWNSTREAM AREAS OF SENSITIVE TERRAIN OR
URBAN LAND SURFACES MAY ALSO BE SLIGHTLY MORE SUSCEPTIBLE TO FLASH
FLOODING. THIS RISK SHOULD EXIST FOR AT LEAST A FEW HOURS TONIGHT
-- PERHAPS THROUGH 09Z.
COOK
..PLEASE SEE WWW.WPC.NCEP.NOAA.GOV FOR GRAPHIC PRODUCT
ATTN...WFO...BMX...FFC...HUN...MRX...
ATTN...RFC...ALR...ORN...NWC...
LAT...LON 35088541 34878407 34438365 33768398 33458587
33918739 34908722
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