MESOSCALE PRECIPITATION DISCUSSION 0748...CORRECTED
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
522 PM EDT THU OCT 20 2016
 
CORRECTED FOR AREAS AFFECTED

AREAS AFFECTED...WESTERN & CENTRAL PA...CENTRAL NY 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 202115Z - 210315Z
 
SUMMARY...INCREASING THREAT FOR FLASH FLOODING THROUGH EVENING
HOURS ACROSS RUGGED TERRAIN.

DISCUSSION...21Z SFC ANALYSIS INDICATES A WEAK SURFACE WAVE AT THE
NORTHERN END OF PERSISTENT SW-NE STATIONARY FRONT JUST NORTH OF
KDUJ...A WARM FRONT BULGES NORTHWARD ACROSS CENTRAL PA BEFORE
EXTENDING SE TOWARD THE MOUTH OF THE DELAWARE RIVER.  GOES-EAST WV
LOOP DENOTES NICELY ANTI-CYCLONICALLY CURVED 140KT JET ACROSS
SOUTHERN CANADA WITH A LARGE BROAD JET ENTRANCE REGION EXTENDING
SOUTHWARD TOWARD THE BASE OF THE TROF IN THE TN VALLEY.  THIS
PROVIDES AN EXCELLENT ENVIRONMENT FOR ASCENT ACROSS THE DISCUSSION
REGION WITH FAVORABLE RIGHT ENTRANCE DYNAMICS ACROSS THE REGION
CURRENTLY THAT WILL STEADILY INCREASE THROUGHOUT THE EVENING AS
THE TROF SLIDES FROM POSITIVE TO MORE NEUTRAL ORIENTATION. 

THE LOWER LEVEL ENVIRONMENT WILL ALSO RESPOND WITH INCREASING 850
LLJ FROM 20 KTS TOWARD 45-50 KTS BY 02Z THOUGH FROM TWO STREAMS. 
CIRA LAYERED TPW DENOTED DEEP UNIDIRECTIONAL SWLY PLUME OF MST
AT/ALONG THE FRONTAL BOUNDARY WITH THE NOSE OF INCREASED MST
POINTED TO CENTRAL PA...CONCURRENTLY SOUTHERLY/SELY FLOW ALONG THE
WARM FRONT ALSO IS PROVIDING FLUX OF WARMER AIR/MOISTURE OFF THE
NORTH ATLANTIC.  THIS CONFLUENCE IN THE WARM SECTOR ACROSS CENTRAL
PA WILL INCREASE TPWS TOWARD THE 1.5" RANGE GIVEN THE WESTERLY
PLUME WILL MOISTEN PROFILES FROM 7H-4H AND INSTABILITY (1500 J/KG
MLCAPES) BUILT UP ACROSS MD/N VA WILL ADVECT TO SUPPORT INCREASED
CONVECTIVE VIGOR BY 22-23Z RANGE.  GIVEN THE CONFLUENCE AND
ISENTROPIC ASCENT OVER THE WARM FRONT THIS WILL EXTEND INTO
CENTRAL NY WITH TRAINING OF INCREASINGLY EFFICIENT RAINFALL
PRODUCING CONVECTION THROUGH 00Z-03Z.  HI-RES CAMS HAVE BEEN
FAIRLY CONSISTENT PROVIDING CONFIDENCE IN RAINFALL TOTALS ACROSS
NORTH CENTRAL PA/S CENTRAL NY TOWARD THE 2-4" RANGE.  GIVEN THE
TERRAIN AND LOWERED FFG FROM THIS AND SOME RAINFALL THIS
MORNING...FLASH FLOODING CONDITIONS ARE POSSIBLE PARTICULARLY
AFTER 00Z AS CELL MOTION PROFILES SUPPORT INCREASED TRAINING. 

GALLINA

ATTN...WFO...BGM...BUF...CTP...PBZ...

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

LAT...LON   43467605 43137525 42277578 40997718 39987866 
            39918045 41657890 42597761