179
AWUS01 KWNH 120243
FFGMPD
NCZ000-SCZ000-GAZ000-TNZ000-KYZ000-ALZ000-120742-
MESOSCALE PRECIPITATION DISCUSSION 1016
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1042 PM EDT TUE AUG 11 2026
AREAS AFFECTED...IN AND NEAR MIDDLE & EASTERN TN
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE
VALID 120242Z - 120742Z
SUMMARY...CELL MERGERS ACROSS THE REGION COULD LEAD TO HOURLY RAIN
AMOUNTS TO 2.5", WHICH COULD LEAD TO WIDELY SCATTERED INSTANCES OF
FLASH FLOODING.
DISCUSSION...A LINE OF THUNDERSTORMS IS MOVING SOUTHWARD THROUGH
NORTHEAST TN AND FAR SOUTHERN KY. THE LINE IS MOVING DOWN AN
INSTABILITY GRADIENT, WITH THE MAIN INSTABILITY POOL ACROSS
PORTIONS OF WESTERN AND MIDDLE TN, WHERE MUCAPE IS 4000-4500 J/KG.
EFFECTIVE BULK SHEAR OF 30 KTS IS ORGANIZING THE CONVECTION. OUT
AHEAD OF THE LINE, INDIVIDUAL/LESS ORGANIZED THUNDERSTORMS ARE
FORMING ACROSS MIDDLE AND EASTERN TN AS FAR AS FAR NORTHWEST GA.
WHILE INFLOW AT 850 HPA IS MODEST, NEAR 15 KTS, THIS IS 2-3 TIMES
THE MAGNITUDE OF THE MEAN 850-400 HPA WIND. PRECIPITABLE WATER
VALUES ARE ~1.8".
THE EXPECTATION IS FOR CELL MERGERS WHICH WOULD BRING HOURLY RAIN
AMOUNTS UP TO 2.5" LOCALLY, WHICH WOULD BE PROBLEMATIC OVER THE
REGION AS THIS WOULD EXCEED THE THREE HOUR FLASH FLOOD GUIDANCE
VALUES AND OVER SOME OF THE MORE SENSITIVE TERRAIN OF THE
SOUTHERNMOST APPALACHIANS. ANOTHER POTENTIAL PROBLEM IS THAT CELL
TRAINING ALONG A NW-SE OR NNW-SSE AXIS AS CELLS BACKBUILD TO THE
EFFECTIVE/OUTFLOW BOUNDARY, COULD BECOME MORE ESTABLISHED AT THE
850 HPA WIND INCREASES 5-10 KT BY THE END OF THE MPD PERIOD WHICH
COULD MAKE THE FLASH FLOODING POTENTIAL HIGHER. HOURLY AMOUNTS TO
2.5" WITH LOCAL TOTALS TO 4" ARE POSSIBLE, WHICH COULD LEAD TO
WIDELY SCATTERED INSTANCES OF FLASH FLOODING.
ROTH
..PLEASE SEE WWW.WPC.NCEP.NOAA.GOV FOR GRAPHIC PRODUCT
ATTN...WFO...BMX...FFC...GSP...HUN...JKL...LMK...MRX...OHX...
ATTN...RFC...ALR...ORN...TIR...NWC...
LAT...LON 36908648 36618467 35848342 34638332 34148462
34608591 35808692
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