MESOSCALE PRECIPITATION DISCUSSION 0308
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
522 PM EDT SUN JUL 05 2015
 
AREAS AFFECTED...EASTERN KENTUCKY...NORTHEAST TENNESSEE...SOUTHERN
VIRGINIA...NORTHEAST NORTH CAROLINA...WEST VIRGINIA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 052121Z - 060321Z
 
SUMMARY...SLOW MOVING EFFICIENT HEAVY RAINFALL PRODUCING CELLS TO
CONTINUE EXPAND NEAR THE UPPER LOW IN THE APPALACHIANS WITH HOURLY
RATES NEAR FLASH FLOOD GUIDANCE.  ADDITIONAL FLASH FLOOD THREAT
FOR SLOW MOVING STRONGER CELLS ALONG THE WARM FRONT ALONG THE
NC/VIRGINIA BORDER. 

DISCUSSION...WELL DEFINED SLOW MOVING VERTICALLY STACKED LOW NEAR
THE CUMBERLAND GAP HAD SUFFICIENT CLEARING THROUGHOUT THE DAY TO
ALLOW INSTABILITIES TO INCREASE INTO THE 2000 J/KG RANGE NORTH AND
EAST INTO WEST VIRGINIA.  CONVECTION HAS RECENTLY DEVELOPED WITH
LIKELIHOOD OF UPTICK OF VERTICAL DEPTH WITH TIME WITHIN THE AREA
OF GREATEST PVA IN WEST VIRGINIA AND GOOD UPPER LEVEL DIVERGENCE
TO SUPPORT STRENGTHENING UPDRAFTS.  GIVEN DEPTH OF THE
LOW...STEERING FLOW IS SLACKED WITH SLOW CELL MOTIONS LEADING TO
THE POTENTIAL FOR TOTALS LIKELY TO EXCEED SHORT TERM FLASH FLOOD
GUIDANCE VALUES GIVEN THE AVAILABLE MOISTURE PER 1.6-1.7" TOTAL
PWATS.  RATES IN THE 1.5"/HR RANGE ARE EXPECTED ACROSS E KY/W
VA/NE TN WITH CONVERGENT BANDS...HIGHER TOTALS INTO THE 3-4" RANGE
ARE POSSIBLE AS SUGGESTED BY HRRR AND FSL-EXPERIMENTAL HRRR AND
NAM-CONEST WITHIN THE DEFORMATION ZONE NORTH AND WEST OF THE LOWS
TRACK.  

FURTHER EAST ALONG THE VIRGINIA/NORTH CAROLINA LINE... A WELL
DEFINED STATIONARY FRONT JUST NORTH OF THE BOARDER HAS ALLOWED FOR
MOISTURE TO POOL ALONG IT WITH 1.9" TOTAL PWATS BEING ANALYZED. 
THOUGH INSTABILITIES ARE ABOUT 2000 J/KG...DEEP MOISTURE
CONVERGENCE ALONG THE BOUNDARY HAS BEEN SUFFICIENT FOR CONVECTIVE
DEVELOPMENT.  UPPER LEVEL FLOW IS SLACKED WITH 850-300MB MEAN
WINDS IN THE 15 KT RANGE OUT OF THE SOUTHWEST WITH SOME TURNING
TOWARD EAST OUT TOWARD THE ATLANTIC COAST.  THIS SUPPORTS SLOW
CELL MOTIONS WITH POTENTIAL FOR SLOWER MOTIONS REGARDING ANY
RIGHT-TURNING CONVECTION. THIS WOULD SUPPORT MERGERS AND PROLONGED
HEAVY RAINFALL PRODUCTION POTENTIALLY LEADING TO ISOLATED FLASH
FLOODING.  AS WARM FRONT LIFTS INTO VIRGINIA THREAT FOR FLASH
FLOODING INCREASES WITH LOWER GUIDANCE VALUES WITHIN THE JAMES
RIVER WATERSHED....THIS IS SUGGESTED WITH THE SSEO MEAN PAINTING
1.5-2.5" MAKING 3HR FFG EXCEEDANCE PROBABILITIES GREATER THAN 50
PERCENT BY 0100Z...OBVIOUSLY GIVEN IT IS THE MEAN...THERE IS
SUPPORT FOR EVEN HIGHER LOCALIZED TOTALS IN THIS AREA.  

GALLINA

ATTN...WFO...AKQ...GSP...JKL...LWX...MHX...MRX...PBZ...RAH...
RLX...RNK...

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

LAT...LON   39318065 39067947 38677920 37827909 37727716 
            36837522 36207547 36377749 36647949 36658129 
            36158209 36028289 36638305 36708385 37498401 
            38178266 38888149