Graphic for MPD #0190
MESOSCALE PRECIPITATION DISCUSSION 0190
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
354 AM EDT FRI MAY 05 2017

AREAS AFFECTED...WESTERN VA...WEST CENTRAL MD...SOUTH CENTRAL
PA...EASTERN WV

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 050800Z - 051330Z

SUMMARY...A FEW MORE HOURS OF OROGRAPHICALLY ENHANCED SHOWERS AND
INCREASED LOCALIZED RAINFALL CAPABLE OF LOW END FLASH FLOODING
CONDITIONS NEAR ALONG THE BLUE RIDGE AND SHENANDOAH RANGES THROUGH
13-14Z.

DISCUSSION...GOES-E WV LOOP INDICATES BROADENING AREA OF
DIFFLUENCE ALOFT WITH DPVA FROM APPROACHING CORE OF UPPER
LOW...SUPPORTING BROAD LARGE SCALE ASCENT AND SURFACE PRESSURE
FALLS ACROSS SW WV ATTM.  A SUBTLE SHORTWAVE SOUTH OF THE SPLIT IN
THE WARM CONVEYOR BELT HAS LIFTED THROUGH THE FRONT RANGES OF THE
APPALACHIANS INTO SE WV ALLOWING FOR WARM SECTOR TO INTERSECT THE
HIGHER TERRAIN WITH MID 60S TDS AND WEAK INSTABILITY OF 150-300
J/KG PER RAP ANALYSIS...FEEDING SHOWERS AND EMBEDDED CONVECTION
WITHIN CONFLUENCE ALONG A PRE-FRONTAL TROF.  CELL MOTIONS WITHIN
THE LINE ARE NEARLY NORTH ALLOWING FOR TRAINING WITHIN THE
CONFLUENT LINE.  STRONG SSWLY 850MB FLOW 45-50KTS NORTH INCREASING
TO 50-60KTS NEARER THE BOUNDARY IS AT A MODEST OBLIQUE ANGLE TO
THE BLUE RIDGE ENOUGH TO SUPPORT SOME OROGRAPHIC ASCENT AHEAD OF
THIS MAIN CONVECTIVE CORE. THIS ALLOWS FOR A FEW HOURS OF WARM
SECTOR ASCENT BEFORE MAIN HEIGHT FALLS FROM THE SWLY SWEEP THE
CONFLUENCE LINE OFF THE TERRAIN TOWARD 12-13Z FURTHER NORTH NEAR
WEST CENTRAL MD AND PA (LIMITING GREATEST MAGNITUDES OF HEAVY
RAINFALL AND THEREFORE FLASH FLOODING THREAT THERE).

AS SUCH .25-.5"/HR RAINS IN THE BROAD OROGRAPHIC ASCENT ALONG WITH
THE 1-1.25"/HR (FOR ABOUT AN HOUR) DEEPER CELLS ALONG THE
CONFLUENT TROF SUPPORTS AN ADDITIONAL 1.5-2.5" TOTALS OVER THE
NEXT FEW HOURS...POTENTIALLY LEADING TO AS MUCH AS 4-4.5" IN MOST
FAVORED TOPOGRAPHY THROUGH THE EVENT.  THIS MAY POSE AT LEAST A
SHORT TERM FLASH FLOODING CONCERN IN THE EARLY HOURS...THOUGH THE
THREAT DRAMATICALLY REDUCES AS THE PRE-FRONTAL TROF SHIFTS EAST OF
THE TERRAIN (WITH ONLY URBAN CONCERNS OVER DC METRO TOWARD 13-14Z.


GALLINA

ATTN...WFO...CTP...LWX...RNK...

ATTN...RFC...MARFC...SERFC...

LAT...LON   40237754 39907724 39407745 38837783 38267814
            37927844 37537875 37297897 37057934 37387984
            37957996 38777938 39737867 40127824


Last Updated: 354 AM EDT FRI MAY 05 2017