MESOSCALE PRECIPITATION DISCUSSION 0221
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
501 PM EDT SUN JUL 27 2014
 
AREAS AFFECTED...ERN KY...ERN TN...SW VA...WRN NC 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 272059Z - 280129Z
 
SUMMARY...A RISK OF FLASH FLOODING WILL ACCOMPANY SEVERE
WEATHER...AS INCREASINGLY DEEP ASCENT PROMOTES BACKBUILDING AND
TRAINING OF SUPERCELLS AND OTHER STORM MODES. THIS EPISODE MAY
LAST SEVERAL HOURS...WHILE THE ZONE IN WHICH NEW CELLS INITIATE
WILL MOVE SLOWLY SOUTHEAST.

DISCUSSION...THOUGH REPORTS OF FLASH FLOODING WERE LACKING AS OF
2045Z...SEVERAL WARNINGS WERE NOTED WHERE DUAL-POL RADAR HAD
ESTIMATED AND A FEW MESONET GAUGES HAD OBSERVED NEAR TWO INCHES OF
RAIN IN EASTERN KY. THE STORM MODE WAS LARGELY SUPERCELLULAR...BUT
THE LARGE SCALE FLOW WAS FAVORABLE FOR BACKBUILDING AND TRAINING
WHERE A ZONE OF CONVERGENT 850 MB FLOW WAS SET BENEATH INCREASING
MID LEVEL HEIGHT FALLS. BUNKERS RIGHT-MOVING SUPERCELL MOTION WAS
ALIGNED NEARLY PARALLEL TO CORFIDI VECTORS FOR A FORWARD
PROPAGATING MCS. LOCAL UPSCALE GROWTH OF SOME SUPERCELL CLUSTERS
SHOULD OCCUR AS THE NUMBER OF CELLS AND COLD POOLS INCREASES THIS
EVENING.

MODEL SOLUTIONS HAVE NOT BEEN IDEAL...BUT THE 12Z NSSL WRF SEEMS
TO HAVE A GOOD SOLUTION IN THIS REGION WHEN SHIFTING ITS
CONVECTION SOUTHWARD TO MATCH REALITY. BOTH THE NSSL WRF AND
RECENT HRRR RUNS PREDICT BACKBUILDING TOWARD NORTH-CENTRAL TN
ALONG THE AXIS OF 850 MB CONVERGENCE...AND SURVIVAL OF ACTIVITY
EASTWARD INTO PORTIONS OF VA/NC. THIS...ALONG WITH NEW DEVELOPMENT
ALONG OUTFLOWS...MAY YIELD TWO-INCH RAINFALL IN SEVERAL
LOCATIONS...WITH ISOLATED MAX AMOUNTS CLOSER TO 2.5 INCHES. THE
FAVORABLE SETUP FOR HEAVY RAIN WILL EXPAND SLOWLY SOUTH AND
EAST...UNTIL THE 850 MB FLOW VEERS WITH THE PASSAGE OF AN UPPER
JET STREAK FARTHER NORTH...AROUND 02-04Z.

ATTN...WFO...RNK...RLX...GSP...MRX...JKL...LMK...OHX...

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

LAT...LON   35978087 35558181 35478304 35748435 36168548 36538589
            36928570 37378491 37498409 37488244 37168111 36578068
            35978087