MESOSCALE PRECIPITATION DISCUSSION 0708
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
425 PM EDT WED SEP 28 2016
 
AREAS AFFECTED...VA/MD 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 282025Z - 290125Z
 
SUMMARY...INCREASING CONVECTIVE COVERAGE WILL LIKELY RESULT IN
SOME FLASH FLOOD POTENTIAL OVER THE NEXT SEVERAL HOURS.

DISCUSSION...CONVECTION CONTINUES TO INCREASE IN COVERAGE ACROSS
EASTERN VA INTO SOUTHERN MD. THE BEST SYNOPTIC FORCING REMAINS TO
THE WEST OF THE AREA. HOWEVER INCREASING SOUTHERLY LOW LEVEL FLOW
IS ENHANCING MOISTURE TRANSPORT UP AND OVER THE STALLED OUT
BOUNDARY SITUATED ACROSS SOUTHERN VA. AS WE GO TROUGH THE NEXT
SEVERAL HOURS SYNOPTIC FORCING WILL ONLY CONTINUE TO
INCREASE...WITH THE REGION BEGINNING TO FEEL THE IMPACT FROM A
SUBTLE FEATURE NOTED ON WATER VAPOR IMAGERY MOVING UP THE NC
COAST...AND A MORE WELL DEFINED FEATURE TRACKING EAST ACROSS THE
OHIO VALLEY. LOW LEVEL FLOW IS FORECAST TO INCREASE AS WELL. THUS
SEEMS LIKELY THAT CONVECTION WILL CONTINUE TO REGENERATE
NEAR/NORTH OF THE BOUNDARY AND PUSH NORTHEASTWARD. THE ENVIRONMENT
IS ALSO FAVORABLE FOR SOME RIGHT MOVING SUPERCELLS...WHICH WILL
LIKELY LOCALLY ENHANCE CELL MERGERS. 

RECENT RUNS OF THE HRRR AND EXPERIMENTAL HRRR SUGGEST LOCALIZED
RAINFALL TOTALS OF 3-5" ARE POSSIBLE THROUGH 02Z ACROSS PORTIONS
OF SOUTHEAST VA WITH THIS ACTIVITY. THIS SEEMS
REASONABLE...ALTHOUGH BASED ON RECENT RADAR TRENDS THE 17Z AND 18Z
HRRR AND EXPERIMENTAL HRRR MAY BE SLIGHTLY TOO FAR SOUTH. AMOUNTS
WILL PROBABLY BE LESS FURTHER NORTH INTO SOUTEHRN MD...HOWEVER
PORTIONS OF THIS AREA RECEIVED UPWARDS OF 4" OF RAIN THIS MORNING.
THUS THIS ADDITIONAL RAINFALL MAY STILL BE ENOUGH TO BEGIN TO
CAUSE SOME FLASH FLOOD ISSUES.

FOR NOW THE FOCUS WILL LIKELY REMAIN ACROSS SOUTHEAST VA INTO
SOUTEHRN MD WHERE THE INCREASING LOW LEVEL FLOW IS PERPENDICULAR
TO THE STALLED OUT WEST TO EAST BOUNDARY. THE FLASH FLOOD THREAT
WILL LIKELY EXPAND WEST AND NORTH INTO THE REST OF NORTHERN VA/MD
THIS EVENING INTO TONIGHT AS THE JET/SHORTWAVE ENERGY CURRENTLY
OVER KY/TN MOVES EAST RESULTING IN CONTINUED INCREASED CONVECTIVE
COVERAGE OVER VA. FUTURE MPD ISSUANCES ARE LIKELY TO ADDRESS THIS
CONCERN AS WELL FOR THE CURRENT LINES OF CONVECTION ACROSS NC AND
SOUTHWEST VA.

CHENARD

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

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

LAT...LON   38797633 38267584 36907626 36767665 36957751 
            37347819 38327764 38747659 
!