MESOSCALE PRECIPITATION DISCUSSION 0294
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1006 PM EST SAT DEC 21 2013
 
AREAS AFFECTED...CENTRAL TN...CENTRAL AND EASTERN KY...SOUTHEAST
IN...OH...WESTERN WV 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 220305Z - 220715Z
 
SUMMARY...THE FLASH FLOOD THREAT CONTINUES AS A STRONG SQUALL LINE
ADVANCES NORTHEASTWARD WITH INTENSE SHORT-TERM RAINFALL RATES.

DISCUSSION...LATEST RADAR IMAGERY SHOW A WELL-DEFINED MCS IN THE
FORM OF A SQUALL LINE...WITH EMBEDDED LINE SEGMENTS MOVING THROUGH
THE OH VALLEY AND GRADUALLY APPROACHING THE TN VALLLEY. WHILE
PORTIONS OF THE LINE ARE QUITE PROGRESSIVE GIVEN THE DISTINCT
SEVERE MODE OF THE CONVECTION...THE RAINFALL RATES ARE STILL QUITE
INTENSE...AND LOCALLY ON THE ORDER OF 1 TO 1.5 INCHES/HR. EVEN
BEHIND THE MAIN CONVECTIVE LINE...THERE IS PLENTY OF MDT/HVY
STRATIFORM RAIN THAT AT LEAST FOR A COUPLE OF ADDITIONAL HOURS
WILL CONTRIBUT TO HVY STORM TOTALS.

THE CONVECTIVE LINE SHOULD BE SUSTAINABLE THE NEXT SEVERAL HOURS
AS LARGE SCALE FORCING CONTINUES OUT AHEAD OF AN APPROACHING UPPER
TROUGH AND WHILE INTERACTING WITH AN ANOMALOUS MOISTURE TRANSPORT
REGIME THAT INCLUDES A NOSE OF 1.6 TO 1.8 INCH PWATS MOVING UP
THROUGH TN/OH VALLEYS. THE LATEST RAP ANALYSIS INDICATES A 60 TO
80 KT LOW LEVEL JET PROVIDING THE MOISTURE AND FAVORABLE
THERMODYNAMIC ENVIRONMENT.

GIVEN LOCALLY MOIST/SATURATED SOILS...AND SUCH INTENSE SHORT-TERM
RAINFALL RATES WITH THE CONVECTIVE LINE...THERE WILL STILL BE A
THREAT FOR AT LEAST SOME FLASH FLOODING. THIS WILL ESPECIALLY BE
THE CASE FROM CENTRAL KY NEWD UP INTO MUCH OF OH WHERE FFG VALUES
ARE NOTABLY LOWER. RECENT SNOWMELT HAS LOCALLY CONTRIBUTED TO THIS
CONCERN...AND THUS ELEVATING THE FLASH FLOOD RISK.

ORRISON

ATTN...WFO...PBZ...RLX...CLE...MRX...JKL...ILN...LMK...IWX...
OHX...IND...HUN...PAH...MEG...

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

LAT...LON   41538274 41638156 41188052 40368046 39298108 38198192
            36848339 35428573 35108721 35208828 35938866 37098786
            38698660 40088508 41238356 41538274