MESOSCALE PRECIPITATION DISCUSSION 0493
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
154 AM EDT SAT JUL 15 2017

AREAS AFFECTED...SOUTHEASTERN VA...EXT NORTHEASTERN NC

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

VALID 150555Z - 150930Z

SUMMARY...TRAINING HIGHLY EFFICIENT RAINFALL EXPECTED OVER NEXT
FEW HOURS POTENTIALLY LEADING TO FLASH FLOODING CONCERNS
PARTICULARLY IN URBAN LOCALS. 

DISCUSSION...CIRA LAYERED PW DENOTES A NARROW BAND OF ELEVATED
MOISTURE IN THE 7-3H LAYERS ACROSS S VA WITH A GRADIENT JUST SOUTH
OF THE VA/NC BORDER IN TANDEM WITH RAP 850MB FLOW BECOMING
INCREASINGLY CONFLUENT ALONG THE BORDER...LEADING TO TOTAL PWS IN
THE 2.25-2.4" RANGE.  ADDITIONALLY...WV SHOWS A SHEARING WAVE
APPROACHING ALONG THE MOISTURE GRADIENT ACROSS NW VA WITH SOME
ADDITIONAL RIDGING FROM SUGGESTIVE OF MID TO UPPER LEVEL JET
ENTRANCE REGION ACROSS SE VA/NE NC FURTHER SUPPORTING EVACUATION
ALOFT FOR STRONGER UPDRAFTS.  RECENT IR/RADAR MOSAIC ALSO DEPICTS
THE LARGER SCALE ASCENT REGION TO BE EXPANSIVE ENOUGH FOR UPSTREAM
DEVELOPMENT SOUTH OF THE PETERSBURG REGION.

ALL FACTORS CONSIDERED...CONVECTION WILL BE INCREASINGLY EFFICIENT
WITH RAIN RATES OVER 2.5"/HR...AND RECENT 15 MINUTE .8" TOTAL AT
KNGU IS SUGGESTIVE OF HIGHER RATES POSSIBLE.  COMBINED WITH NEARLY
UNIDIRECTIONAL CLOUD STEERING FLOW TO SUPPORT SOME TRAINING...ONLY
REAL STICKING POINT WILL BE SOME MODEST SOUTHWARD PROPAGATION. 
STILL THERE IS LIKELY SUFFICIENT TIMING/REPEATING CONVECTION FOR
2-4" TOTALS TO OCCUR OVER THE NEXT 3-4 HOURS...WHICH MATCHES WELL
WITH 03Z ESRL EXP. HRRR (BEST INITIALIZED COMPARED TO CURRENT
SETUP) AND ACROSS AN URBAN CENTER ONLY INCREASES THE FLASH FLOOD
THREAT.     

GALLINA

ATTN...WFO...AKQ...

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

LAT...LON   37087656 37067609 36927590 36577580 36397577
            36317597 36377676 36607720 36977707