MESOSCALE PRECIPITATION DISCUSSION 0171
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
110 PM EDT WED JUL 02 2014
 
AREAS AFFECTED...CENTRAL/EASTERN PA...NORTHERN NJ...SOUTHEAST
NY...WESTERN MA...SOUTHERN VT 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 021700Z - 022200Z
 
SUMMARY...INCREASING SHOWER AND THUNDERSTORM ACTIVITY EXPECTED
THROUGH THE AFTERNOON. MERGING AND LOCALIZED TRAINING OF CELLS
WILL ENHANCE THE THREAT FOR FLASH FLOODING.


DISCUSSION...THE LATEST VIS IMAGERY SHOWS AN INCREASINGLY AGITATED
AND EXPANSIVE CU/TCU FIELD FROM SOUTHERN PA NORTHEAST INTO
SOUTHEAST NY ALONG AND AHEAD OF A COLD FRONT WHICH IS CROSSING THE
APPALACHIANS ATTM. THE AIRMASS OUT AHEAD OF THE FRONT IS BECOMING
VERY UNSTABLE...WITH SBCAPE VALUES OF 3000 TO 4000 J/KG ALONG AND
WEST OF THE I-95 CORRIDOR INCLUDING THE PIEDMONT AREAS OF NORTHERN
MD/SOUTHEAST PA AND INTO SOUTHEAST NY.

ALREADY THERE ARE SCT HEAVY SHOWERS AND THUNDERSTORMS IMPACTING
PORTIONS OF CENTRAL/NORTHEAST PA AND FAR SOUTHERN NY. OVER THE
NEXT COUPLE OF HOURS...THIS ACTIVITY SHOULD RAPIDLY EXPAND AND
BECOME ORGANIZED IN NATURE WITH MULTIPLE LINEAR SW/NE ORIENTED
BANDS OF STRONG CONVECTION. INCREASING DIURNAL HEATING/SFC-BASED
INSTABILITY COUPLED WITH AN ANOMALOUSLY MOIST AIR MASS EAST OF THE
APPALACHIANS WILL PROVIDE A VERY FAVORABLE THERMODYNAMIC
ENVIRONMENT FOR A SUSTAINABLE AND ORGANIZED CONVECTIVE THREAT
THROUGH THE AFTERNOON AHEAD OF THE FRONT AND ADVANCING GRADUALLY
EAST TWD THE I-95 CORRIDOR.

GIVEN PWATS AS PER LATEST GOES-SOUNDER OF 1.75 TO 2 INCHES EAST OF
THE APPALACHIANS...RAINFALL RATES WILL BE VERY INTENSE...AND
LIKELY ON THE ORDER OF 2 TO 3 INCHES/HR. THE SOUTHWESTERLY NATURE
TO THE LOW AND MID LVL FLOW AHEAD OF THE FRONT WILL TEND TO FAVOR
A THREAT FOR TRAINING CELLS...AND CELL MERGERS WILL BE LIKELY IN
THE SHORT TERM AS CONVECTION BECOMES BETTER ORGANIZED.
THEREFORE...THE THREAT FOR FLASH FLOODING WILL BE ELEVATED...AND
ESP OVER AREAS OF HIGHER TERRAIN. WILL CONTINUE TO MONITOR.

ORRISON

ATTN...WFO...BOX...OKX...ALY...PHI...BGM...CTP...

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

LAT...LON   42137262 40607433 39857571 39727686 39907767 40557766
            41347684 42297576 43107418 42987276 42137262 
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