MESOSCALE PRECIPITATION DISCUSSION 0342
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1136 AM EDT MON JUN 19 2017

AREAS AFFECTED...NE PA...NJ...SE NY...VT...NH...E ME...W MA...NW
CT

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

VALID 191535Z - 192035Z

SUMMARY...INCREASING PRE-FRONTAL CONVECTION WITHIN A SATURATED LOW
LEVEL ENVIRONMENT AND FAIRLY DEEP UNIDIRECTIONAL FLOW SUPPORT
LOCALIZED TRAINING AND FLASH FLOODING POTENTIAL THIS AFTERNOON. 

DISCUSSION...COLD FRONT MOVING THROUGH THE EASTERN MIDWEST IS
PROGRESSING SLOWLY THROUGH THE APPALACHIANS UNDER INCREASINGLY
CONFLUENT MID TO UPPER LEVEL FLOW PER GOES-E WV LOOP.  BLENDED TPW
ANALYSIS SUGGESTS TROPICALLY CONNECTED STREAM ALONG THE EASTERN
SEABOARD IS MELDING WITH THE ENHANCED MOISTURE POOLED AHEAD OF THE
BOUNDARY THROUGH THE MID-ATLANTIC INTO THE NEW ENGLAND.  WV LOOP
ALSO DENOTES WILL SLIGHTLY CYCLONICALLY CURVED 110KT 3H JET OVER
SE CANADA WITH A WEAK INFLECTION NEAR SE OH ADVANCING NORTHEAST
PROVIDING EXCELLENT RIGHT ENTRANCE ASCENT DYNAMICS THROUGH THE
HUDSON VALLEY TOWARD THE MID-ATLANTIC.  WITHIN THE WARM SECTOR
SURFACE TDS IN EXCESS OF 70S ARE THE NORM WITH SOME LOCALS AS HIGH
AS 75F AND OVERALL TPWS NEAR 2.0" AND WITH FAIRLY CLEAR
SKIES...INSTABILITY HAS RISEN TO 1500-2000 J/KG OF MLCAPE FROM SE
NH TO THE DELAWARE RIVER VALLEY...SLIGHTLY OFFSET OF THE HIGHER
MOISTURE/BETTER FORCING TO THE EAST.

EXPERIMENTAL GOES-16 MESO VISIBLE LOOP SHOWS CONVECTIVE
DEVELOPMENT HAS BROKEN OUT FROM THE S CENTRAL PA TO S HUDSON
VALLEY IN ADVANCE OF THE CONVECTIVE LINE IN CENTRAL PA.  WEAK
CAPPING AND BROAD SCALE ASCENT HAS LEAD TO NARROWLY SPACED
CONVECTIVE DEVELOPMENT. DEEP UNIDIRECTIONAL FLOW IN THE STEERING
LEVELS WILL PROMOTE FAIRLY QUICK FORWARD PROGRESSION TOWARD THE
NORTHEAST AS WELL AS WEAK (LESS THAN 10KTS) PROPAGATION VECTORS
ALIGNING SUPPORTING NORTHEAST ADVANCEMENT AS WELL.  STILL GIVEN
THE OVERALL COVERAGE AND AMPLE MOISTURE/INSTABILITY SUPPORTING
RATES OF 2"/HR THERE IS POTENTIAL FOR THESE CONVECTIVE CELLS TO
NOT NECESSARILY TRAIN...BUT TRACK THROUGH SIMILAR LOCATIONS IN
SOME TIMES SHORT SUCCESSION.  IN ADDITION N-S CONVECTIVE LINE
ASSOCIATED WITH MAIN COLD FRONTAL FORCING/CONVERGENCE WILL ADVANCE
EASTWARD AS WELL PROVIDING AN ADDITIONAL BOUT OF HEAVY RAIN.  AS
SUCH FLASH FLOODING THREAT WILL BE MAINLY DRIVEN BY THESE
ACCIDENTAL REPEATS AND APPEAR MORE RANDOM IN NATURE...WITH POCKETS
OF 2-3" TOTALS POSSIBLE THROUGH THE EARLY EVENING LEADING TO
POSSIBLE FLASH FLOODING CONDITIONS PARTICULARLY IN URBAN CENTERS
AND LOW FFG VALUE AREAS OF S CENTRAL NY AND W VT. 

GALLINA

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

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

LAT...LON   44917164 44887066 43967035 42767181 41397307
            40477413 40497586 41067696 42017630 43167467
            44497285