MESOSCALE PRECIPITATION DISCUSSION 0277
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1050 PM EDT FRI JUN 26 2015
 
AREAS AFFECTED...WESTERN NC, WESTERN VIRGINIAS, EASTERN KY 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 270248Z - 270848Z
 
SUMMARY...THE COMBINATION OF APPROACHING CONVECTION, INCREASING
UPSLOPE FLOW, AND LINGERING INSTABILITY COULD CAUSE FLASH FLOODING
IN STEEP TERRAIN.

DISCUSSION...THE SURFACE ANALYSIS REVEALS A WEAK WAVE ACROSS
NORTHWEST SC WHICH HAS BEGUN INCREASING UPSLOPE FLOW WITHIN THE
TERRAIN TO ITS NORTH PER RECENT FCX VAD WIND PROFILES. 
PRECIPITABLE WATER VALUES ARE 1.3-1.5" PER GPS INFORMATION ACROSS
SOUTHWEST VA, WITH HIGHER VALUES ACROSS WV.  IN ADDITION,
CONVECTION FROM NORTHEAST TN, EASTERN KY, AND NORTHWEST NC IS
MOVING INTO THE AREA AT ~20 KTS, THE MAGNITUDE OF THE FORWARD
PROPAGATING CONVECTIVE VECTORS.  UPSTREAM MUCAPES (USING 850 HPA
WINDS) ARE 1000-2000 J/KG, WHICH SHOULD BE SUFFICIENT CONSIDERING
MOISTENING ATMOSPHERIC PROFILES.

THE EXPECTATION IS FOR ACTIVITY FROM THE SOUTHWEST OF THE REGION
TO MOVE INTO THE REGION AND FOR NEW ACTIVITY TO FORM ALONG
PORTIONS OF THE BLUE RIDGE MOUNTAINS AS UPSLOPE FLOW INCREASES. 
THIS ACTIVITY SHOULD SHIFT NORTHEAST UP THE TERRAIN AS AN INVERTED
TROUGH AS THE SURFACE/850 HPA MOVES NORTHEAST WITH TIME.  SOME
REDEVELOPMENT ALONG THE BLUE RIDGE IS POSSIBLE AS INITIAL CELLS
PROPAGATE EASTWARD AT 20 KTS AWAY FROM THE TERRAIN.  RAP FORECASTS
INDICATE MINIMAL CHANGE IN THE MUCAPES ACROSS NC AND SOUTHERN VA
OVERNIGHT.  HOURLY RAIN RATES UP TO 2" ARE POSSIBLE CONSIDERING
THE AVAILABLE MOISTURE.  THERE IS A MODEST SIGNAL FOR LOCAL
AMOUNTS OF 2-4" WITHIN THE MESOSCALE GUIDANCE NEAR THIS AREA.  THE
PERFORMANCE OF THE MESOSCALE QPF GUIDANCE APPEARS SUB-PAR PER
RECENT RADAR IMAGERY.  THE 12Z ARW AND RECENT RAP/HRRR RUNS SEEM
TO BE HANDLING THE CONVECTIVE POSSIBILITIES THE BEST.  

ROTH

ATTN...WFO...AKQ...CAE...GSP...JKL...LWX...MRX...RAH...RLX...
RNK...

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

LAT...LON   39008093 38767904 37997761 37127789 35847888 
            35207993 34908095 35108118 35698167 36548266 
            37368298 38328235