MESOSCALE PRECIPITATION DISCUSSION 0387
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1137 AM EDT TUE JUN 28 2016
 
AREAS AFFECTED...NORTHEAST NY & NORTHERN NEW ENGLAND 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 281536Z - 282136Z
 
SUMMARY...THUNDERSTORMS ARE EXPECTED TO INCREASE IN COVERAGE IN
ASSOCIATION WITH A COLD FRONT, THE TOPOGRAPHY, AND A POSSIBLE
DIFFERENTIAL HEATING BOUNDARY.  HOURLY RAIN RATES UP TO 2", WITH
LOCAL AMOUNTS OF 2-4", COULD LEAD TO FLASH FLOODING.

DISCUSSION...A SLOW-MOVING COLD FRONT IS EDGING ACROSS NY STATE,
WITH THE MAIN WAVE NEAR MONTREAL.  THUNDERSTORMS HAVE RECENTLY
BEGUN TO DEVELOP IN THIS REGION.  SOME SLIGHT WIND CONVERGENCE
APPEARS TO EXIST WITH THE SOUTHERN EDGE OF THE LOW CLOUD SHIELD
ACROSS NORTHERN ME.  PRECIPITABLE WATER VALUES OF ~1.25" EXIST IN
THE AREA, WHICH AT ELEVATION IN THE NORTHERN APPALACHIANS WOULD BE
EQUIVALENT TO 1.5-2" AT SEA LEVEL.  INFLOW AT 850 HPA IS 20 KNOTS
FROM THE SOUTHWEST PER VAD WIND PROFILES, SIMILAR TO THE MEAN
850-400 HPA WIND (UNIDIRECTIONAL WINDS WITH HEIGHT).  MLCAPE
VALUES ACROSS THE AREA ARE BUILDING AS SKIES ARE MOSTLY SUNNY, UP
TO 500-1000 J/KG AT 15Z.

THE EXPECTATION IS FOR LOW-LEVEL INFLOW TO BECOME MORE CONVERGENT
AND BACK SOMEWHAT MORE WITH TIME NEAR AND JUST SOUTH OF THE
INTERNATIONAL BORDER AS 850 HPA WINDS RISE TO 25-30 KTS.  MLCAPES
ARE LIKELY TO BUILD TO AT OR ABOVE 1500 J/KG.  THE CLOUD
EDGE/DIFFERENTIAL HEATING BOUNDARY ACROSS NORTHERN ME COULD BE A
PLAYER THUNDERSTORM-WISE DURING THE DAY TODAY.  THE MORE RELIABLE
GUIDANCE SHOWS CONVECTION INCREASING IN COVERAGE WITH TIME, WITH
LOCAL AMOUNTS OF 2-4" ANTICIPATED, WHICH COULD FALL QUICKLY. 
HOURLY RAIN RATES UP TO 2" ARE POSSIBLE WHERE CELLS MERGE OR
TRAIN.  THE 06Z SSEO NEIGHBORHOOD PROBABILITIES OF EXCEEDING THE
THREE HOURLY 10 AND 25 YEAR RECURRENCE INTERVALS WERE >=50% FROM
NORTHEAST NY THROUGH NORTHERN ME, WITH NORTHERN ME SHOWING >=50%
CHANCE OF EXCEEDING THEIR 100 YEAR RECURRENCE INTERVAL FOR THREE
HOURS BETWEEN 18-22Z.

ROTH

ATTN...WFO...ALY...BTV...CAR...GYX...

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

LAT...LON   47516912 46826774 45476927 44207147 43697441 
            44927392 45957226