MESOSCALE PRECIPITATION DISCUSSION 0583
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
223 PM EDT FRI JUL 28 2017

AREAS AFFECTED...SOUTHEAST VA...NORTHEAST NC

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

VALID 281820Z - 290000Z

SUMMARY...ADDITIONAL ROUNDS OF HEAVY SHOWERS AND THUNDERSTORMS ARE
EXPECTED THIS AFTERNOON. GIVEN EARLIER HEAVY RAINS AND SATURATING
SOIL CONDITIONS...SOME RUNOFF PROBLEMS AND/OR FLASH FLOODING IS
POSSIBLE.

DISCUSSION...RADAR IMAGERY IS SHOWING SOME UPTICK IN CONVECTION
OVER PARTS OF NORTHEAST NC AND ADJACENT AREAS OF SOUTHEAST
VA...WITH THE LATEST GOES-16 EXPERIMENTAL SATELLITE DATA SHOWING
COOLING CONVECTIVE TOPS. SURFACE OBSERVATIONS SHOW A FAIRLY
WELL-DEFINED A SMALL SCALE COLD POOL FROM CONVECTION EARLIER THIS
MORNING SITUATED OVER NORTHEAST NC...WITH AN EFFECTIVE
OUTFLOW/MESOSCALE BOUNDARY LAID DOWN ACROSS THE AREA AS A RESULT.
DIFFERENTIAL HEATING ACROSS THE AREA FROM THE EARLIER CLOUD COVER
HAS ONLY HELPED TO MAINTAIN THIS OVER THE LAST COUPLE OF HOURS.
THE AIRMASS OFF TO THE SOUTHWEST OF THE COLD POOL IS VERY MOIST
AND UNSTABLE...AND WITH A CONFLUENT LOW LEVEL FLOW REGIME OVER THE
COLD POOL AND RESULTING ISENTROPIC LIFT...CONVECTIVE REGENERATION
HAS BEEN OCCURRING AND SHOULD CONTINUE TO OCCUR OVER THE NEXT
SEVERAL HOURS.

PWATS ARE BETWEEN 2 AND 2.25 INCHES...AND WITH A RATHER EFFICIENT
COLUMN OF DEEP MOISTURE...RAINFALL RATES OF UP TO 2.5 TO 3
INCHES/HR WILL BE EXPECTED AS CONVECTION CONTINUES TO REORGANIZE
THIS AFTERNOON. THE LATEST HRRR ALONG WITH THE 12Z ARW/NSSL-WRF
GUIDANCE SUPPORTS POCKETS OF 3 TO 5 INCHES OF ADDITIONAL RAIN
THROUGH 00Z.

GIVEN THE NEARLY SATURATED SOIL CONDITIONS AT LEAST LOCALLY...SOME
RUNOFF PROBLEMS AND FLASH FLOODING WILL BE POSSIBLE.

ORRISON

ATTN...WFO...AKQ...MHX...RAH...

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

LAT...LON   37127662 36777571 35737571 35717677 36007742
            36437777 36977757