MESOSCALE PRECIPITATION DISCUSSION 0094
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
151 PM EDT FRI JUN 07 2013
 
AREAS AFFECTED...NORTHERN VA/DISTRICT OF COLUMBIA/CENTRAL
MD/EASTERN PA/NORTHERN NJ/EASTERN NY... 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 071750Z - 072235Z
 
SUMMARY...A LONG DURATION HEAVY RAINFALL EVENT IS EXPECTED TO
CONTINUE FROM THE DELMARVA UP INTO SOUTHEASTERN NY. RAINFALL RATES
ARE EXPECTED TO INCREASE LATER THIS AFTERNOON/EVENING AS DEEPER
CONVECTION ACROSS NORTHERN NC/SOUTHERN VA LIFTS NORTHWARD.

DISCUSSION...A VERY MOIST AIR MASS IS PRESENT AS INDICATED BY THE
ABOVE 2 INCH PWATS ON THE 12Z SOUNDINGS AT APG/WAL. THIS EASILY
NEARS THE 99TH PERCENTILE FOR THE PWAT CLIMATOLOGY DURING THE
MONTH OF JUNE. TROPICAL MOISTURE CONTINUING TO LIFT NORTHWARD ON
THE EASTERN FLANK OF TROPICAL STORM ANDREA'S BROAD CIRCULATION
WILL KEEP SUCH AN AIR MASS IN PLACE ALONG MUCH OF THE I-95
CORRIDOR FROM THE WASHINGTON D.C. METRO AREA UP INTO COASTAL NEW
ENGLAND. ADDITIONALLY...A BAROCLINIC ZONE HAS SET UP FROM CENTRAL
NJ DOWN ALONG THE CHESAPEAKE RIVER WHICH SHOULD CONTINUE TO
PROVIDE ADEQUATE LOW-LEVEL LIFT FOR ADDITIONAL HEAVY PRECIPITATION.

THE CURRENT RADAR TRENDS SUGGEST ABOVE 1 INCH PER HOUR RAIN RATES
IN THE BANDS OF CONVECTION HAVE DEVELOPED ALONG THE NC/VA BORDER.
A MAJORITY OF THE HIGH-RESOLUTION MODELS INDICATE 2 TO 3 INCHES OF
ADDITIONAL RAINFALL MAY BE POSSIBLE BETWEEN 18-00Z OVER THE
AFFECTED REGION. THIS WILL FALL ON TOP OF THE NOCTURNAL HEAVY
RAINS FROM THE PREDECESSOR RAINFALL EVENT ALONG WITH OVERRUNNING
PRECIPITATION DURING MUCH OF THE MORNING. WHILE FLASH FLOODING IS
NOT IMMINENT...LOCALIZED AREAS OF DIMINISHED FFG MAY EXPERIENCE
SUCH CONDITIONS THIS AFTERNOON/EVENING.


RUBIN-OSTER

ATTN...WFO...OKX...ALY...PHI...BGM...AKQ...CTP...LWX...

ATTN...RFC...MARFC...NERFC...

LAT...LON   38347757 39137753 39717694 40207619 40887551 41817465
            41777385 41377342 40697365 40297425 39877537 39377608
            38207685 38347757