MESOSCALE PRECIPITATION DISCUSSION 0302
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
313 PM EDT FRI JUN 03 2016
 
AREAS AFFECTED...PORTIONS OF THE MID-ATLANTIC STATES 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 031912Z - 040112Z
 
SUMMARY...THUNDERSTORMS ARE BEGINNING TO EXPAND IN COVERAGE WHILE
MOVING MINIMALLY.  WITH HOURLY RAIN RATES UP TO 2", FLASH FLOODING
IS POSSIBLE, PARTICULARLY IN URBAN AREAS.

DISCUSSION...IN THE MESOSCALE, THERE IS A WEAK 1014 HPA WAVE
ACROSS NORTHERN VA NEAR THE APEX OF AN INSTABILITY AXIS ALONG THE
FALL LINE/I-95.  TO THE NORTHEAST OF THIS LOW, THUNDERSTORMS ARE
BEGINNING TO EXPAND IN COVERAGE AND INTENSITY.  MLCAPES OF
500-1500 J/KG LIE ACROSS THE REGION PER SPC MESOANALYSES. 
PRECIPITABLE WATER VALUES OF 1.8-1.9" EXIST IN THE REGION PER GPS
VALUES.  LOW LEVEL INFLOW IS WEAK, ON THE ORDER OF 10 KTS, THOUGH
0-6 KM BULK SHEAR VALUES ARE SUFFICIENT TO HELP ORGANIZE
CONVECTION.

THE CAM GUIDANCE SUGGESTS LOCAL AMOUNTS IN THE 2-4" RANGE, WHICH
COULD FALL QUICKLY.  HOURLY RAIN RATES UP TO 2" ARE POSSIBLE WHERE
SHORT PERIODS OF CELL TRAINING OCCUR.  THE FLOW, OUTSIDE OF THE
LOW-LEVELS IN CENTRAL AND SOUTHERN VA, IS FAIRLY UNIDIRECTIONAL
OUT OF THE WEST IN THIS REGION, WITH SOME AREAS SHOWING 180
DEGREES OF VERTICAL WIND SHEAR.   THE 12Z SSEO NEIGHBORHOOD
PROBABILITIES OF EXCEEDING THE THREE HOUR FLASH FLOOD GUIDANCE
VALUES TRAIL OFF AFTER 01Z, WHICH SHOULD BE THE HORIZON FOR HEAVY
RAIN ISSUES AS INSTABILITY BECOMES EXHAUSTED.  CONSIDERING POCKETS
OF LOWER FLASH FLOOD GUIDANCE VALUES ACROSS PORTIONS OF THE BLUE
RIDGE AS WELL AS URBAN AREAS SUCH AS RICHMOND, WASHINGTON D.C.,
AND BALTIMORE, FLASH FLOODING IS CONSIDERED POSSIBLE.

ROTH

ATTN...WFO...AKQ...CTP...LWX...PBZ...PHI...RLX...RNK...

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

LAT...LON   40167786 39887628 39487486 37377695 36707983 
            37248079 39437908 39717886