MESOSCALE PRECIPITATION DISCUSSION 0049
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
351 PM EDT SUN MAY 19 2013
 
AREAS AFFECTED...CENTRAL AND SOUTHEAST TN...NORTHEAST
AL...NORTHWEST GA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 191950Z - 192300Z
 
SUMMARY...SLOW-MOVING COLD TOPPED CONVECTION FAVORING VERY HEAVY
RAINFALL RATES...WITH SOME TRAINING/REPEATING OF CONVECTION
EXPECTED.

DISCUSSION...LATEST IR SAT IMAGERY SHOWS CLUSTERS OF VERY COLD
TOPPED CONVECTION FOSTERING VERY HEAVY RAINFALL RATES UPWARDS OF 2
TO 3 INCH/HR OVER PORTIONS OF SERN TN AND NWRN GA. THIS AXIS OF
CONVECTION IS EXPECTED TO BE SUSTAINABLE AT LEAST THE NEXT FEW HRS
AS VERY UNSTABLE AIR AIDED BY STRONG DIURNAL HEATING AND AN
ALREADY MOIST BOUNDARY LAYER CONTINUES TO ADVECT IN FROM THE
WEST-SOUTHWEST WHILE INTERACTING WITH A COLD POOL INVOF THE
TN/GA/NC BORDER AREA ALONG WITH ADJACENT COUNTIES. FURTHER AIDED
LOW LEVEL FORCING IS PROXIMITY OF A SLOW-MOVING OUTFLOW BOUNDARY.
THE UPPER FLOW IS ALSO MODERATELY DIFFLUENT WITH THE AID OF A
SHORTWAVE COMPLEX OVER THE OH VALLEY. ADDITIONALLY..WV IMAGERY
SUGGESTS A WEAK JET MAX ADVANCING SOUTHEAST INTO FAR WRN KY AND
WRN TN WHICH WILL AID LARGER SCALE ASCENT THE NEXT FEW HOURS INVOF
AREAS ALREADY SEEING COLD-TOPPED CONVECTION. SO...EXPECTING THE
ONGOING CONVECTION TO AT LEAST SUSTAIN ITS CURRENT LEVEL OF
ORGANIZATION OR PERHAPS EXPAND IN COVERAGE GIVEN MUCAPE VALUES OF
3000 TO 4000 J/KG FEEDING SLOWLY BUT STEADILY INTO THE WRN EDGE OF
THE SLOW-MOVING CONVECTIVE MASS. PORTIONS OF THE THREAT AREA HAVE
ALREADY SEEN EXCESSIVE RAINFALL AMOUNTS...SO FLASH FLOODING IS
LIKELY...AND ESP CONSIDERING THE HIGH MOISTURE CONTENT OF THE
ATMOSPHERE AND SLOW MOVEMENT AND/OR MERGING OF CONVECTIVE CELLS.

ORRISON


ATTN...WFO...MRX...FFC...OHX...BMX...HUN...

LAT...LON   35178492 34568449 34298435 33868439 33668493 33968574
            34538623 35548641 36108615 36218569 35748520 35178492