MESOSCALE PRECIPITATION DISCUSSION 0296
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
825 PM EDT TUE JUN 12 2018

AREAS AFFECTED......FAR NORTHEASTERN ARKANSAS...WESTERN AND
CENTRAL TENNESSEE...WESTERN AND CENTRAL KENTUCKY...NORTHERN
MISSISSIPPI...NORTHERN ALABAMA....

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 130018Z - 130418Z

SUMMARY...A LINE OF THUNDERSTORMS WILL CONTINUE TO EXPAND AND
PROGRESS ACROSS THE LOWER OHIO AND WESTERN TENNESSEE VALLEY THIS
EVENING. THE STRONGEST CELLS WILL BE CAPABLE OF HOURLY RAINFALL
RATES OF 2-2.25" THIS EVENING, WHICH IN SOME AREAS WHERE LOWER FFG
IS PRESENT, MAY LEAD TO FLASH FLOODING.

DISCUSSION...THE LATEST GOES-16 MESO2 VISIBLE AND WATER VAPOR
IMAGERY INDICATED THE REMNANT MESOSCALE-CONVECTIVE VORT CENTER
(MCV) ACROSS SOUTHERN IL, EAST OF SAINT LOUIS. DOWNSTREAM OF THIS
FEATURE, A FOCUSED AREA OF UPPER LEVEL DIVERGENCE IS ALLOWING FOR
WIDESPREAD CONVECTIVE DEVELOPMENT (QUASI-LINEAR) ACROSS PORTIONS
OF THE LOWER OH AND WESTERN TN VALLEYS. HELPING THE ACTIVITY TO
GROW UPSCALE IS THE STRONG AVAILABLE DEEP-LAYER INSTABILITY WITHIN
A FAVORABLY MOIST ENVIRONMENT. PER THE LATEST SPC MESOANALYSIS,
SURFACE-BASED CAPES RANGED BETWEEN 2500-3000 J/KG, WHILE PWATS HAD
CLIMBED BETWEEN 1.75-2.00 (OWING AT LEAST IN PART TO THE MESOSCALE
ENVIRONMENT).

THROUGH THIS EVENING, BASED ON THE CURRENT AND FORECAST WIND
PROFILES, EXPECT THE CONVECTION TO LOSE A BIT OF THE FORWARD OR
DOWNWIND PROPAGATION THAT HAD BEEN OBSERVED THROUGH 00Z. THIS
GIVEN THE BOOST IN SOUTHWESTERLY LOW-LEVEL INFLOW -- CURRENTLY 20
KTS AND PER THE RAP, EXPECTED TO PEAK BETWEEN 25-30 KTS AFTER 01Z.
GIVEN THE WEAKER STEERING FLOW (WNW 850-300 MB MEAN FLOW 10-15
KTS), DO ANTICIPATE SOME CELL TRAINING ON THE SOUTH AND ESPECIALLY
SOUTHWEST PERIPHERY OF THE QLCS THIS EVENING. SUCH WOULD INCREASE
THE PROBABILITY OF HOURLY RAINFALL RATES OF 2-2.25+ INCHES,
ESPECIALLY GIVEN THE AFOREMENTIONED THERMODYNAMIC ENVIRONMENT.
BASED ON THE ANTECEDENT SOIL CONDITIONS (CURRENT 1 AND 3 HOURLY
FFG VALUES), FLASH FLOODING WILL BE POSSIBLE UNDERNEATH THE
STRONGEST THUNDERSTORMS AND/OR WHERE CELLS DO TRAIN.

HURLEY

ATTN...WFO...BMX...HUN...JKL...LMK...MEG...MRX...OHX...PAH...

ATTN...RFC...LMRFC...OHRFC...SERFC...

LAT...LON   38058500 37838408 37278367 36638438 35998506
            35138551 34328625 34018734 33898864 34118993
            34729061 35739062 36048932 36618800 37338728
            37948625