MESOSCALE PRECIPITATION DISCUSSION 0280
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
528 PM EDT SAT JUN 27 2015
 
AREAS AFFECTED...SOUTHEAST PA...CENTRAL AND SOUTHERN
NJ...DE...EASTERN MD...EASTERN VIRGINIA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 272125Z - 280300Z
 
SUMMARY...INTENSE SHOWERS AND THUNDERSTORMS ARE EXPECTED THIS
EVENING...WITH FLASH FLOODING POSSIBLE.

DISCUSSION...A BAND OF INTENSE SHOWERS AND THUNDERSTORMS WILL
GRADUALLY MOVE EAST THIS EVENING AWAY FROM THE I-95 URBAN CORRIDOR
AND PUSH TOWARD THE ATLANTIC COAST. THE CONVECTION IS WELL OUT
AHEAD OF AN APPROACHING COLD FRONT THAT IS PUSHING THROUGH THE OH
VALLEY CURRENTLY...BUT STRONG ASCENT ASSOCIATED WITH THE ARRIVAL
OF A SHORTWAVE TROUGH COUPLED WITH A VERY MOIST AND UNSTABLE
AIRMASS LIFTING UP ACROSS THE MID-ATLANTIC COASTAL PLAIN IS
FOCUSING ORGANIZED CONVECTION. THE CONVECTION IS BEING ENHANCED BY
STRONG LOW LEVEL MOISTURE CONVERGENCE AND PROXIMITY OF A WARM
FRONT THAT CONTINUES TO GRADUALLY LIFT NORTH.

THE HIRES MODELS HAVE BEEN IN REMARKABLY GOOD AGREEMENT IN
DEPICTING THIS AXIS OF CONVECTION THIS AFTERNOON AND EVENING...AND
THE GUIDANCE FAVORS ADDITIONAL FOCUS OF LOCALLY VERY HEAVY
RAINFALL THIS EVENING ACROSS THE MID-ATLANTIC COASTAL PLAIN.
RAINFALL RATES WITHIN THE STRONGEST CORES HAVE BEEN BETWEEN 2 TO
2.5 INCHES/HR...AND THESE RATES ARE EXPECTED TO CONTINUE THROUGH
00Z. AFTER 00Z...THE LATEST HRRR SUGGESTS CONVECTION SHOULD TEND
TO WEAKEN IN RESPONSE TO A LOSS OF DIURNAL HEATING/INSTABILITY. 

RAINFALL AMOUNTS OF 3 TO 5 INCHES WITH LOCALLY HEAVIER AMOUNTS ARE
POSSIBLE...AND GIVEN SUCH INTENSE SHORT-TERM RATES...SOME FLASH
FLOODING WILL BE POSSIBLE.

ORRISON

ATTN...WFO...AKQ...CTP...LWX...PHI...

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

LAT...LON   40447556 40427469 40107392 39517407 38777479 
            38167518 37527544 36757595 36567654 36577714 
            36937735 38047691 39237674 39927642