MESOSCALE PRECIPITATION DISCUSSION 0141
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
602 PM EDT SUN JUN 30 2013
 
AREAS AFFECTED...CT...MA...EASTERN NY...SOUTHERN NH...SOUTHERN ME 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 302201Z - 010121Z
 
SUMMARY...CONDITIONS WHICH LED TO REPORTS OF SIGNIFICANT FLOODING
IN PA/NY/CT WILL PERSIST INTO EARLY EVENING AND MAY EXPAND TOWARD
MA/NH/ME.

DISCUSSION...NOTING REPORTS OF SOME HIGHER-END FLASH FLOODING LATE
THIS AFTERNOON FROM HAWLEY PA AND SHARON CT. WHILE MEAN CLOUD
LAYER WINDS WOULD SUGGEST MORE MOVEMENT...RADAR OBSERVATIONS
REVEALED THE PREFERRED MODE IS SMALLER SCALE MCS DEVELOPMENT WITH
ROTATING CELLS EMBEDDED ALONG THE SOUTHERN AND EASTERN FLANKS.
BUNKERS SUPERCELL MOTION IS ENE AT ONLY 10 KT WHILE CORFIDI
VECTORS PREDICT SOME BACKWARD PROPAGATION...SLOWING MCS MOTION TO
ENE AT 5 KT. THESE SLOW MOTIONS...COUPLED WITH THE RELATIVELY
LOW-TOPPED CONVECTION/LITTLE HAIL PRODUCTION/ AND AN ANOMALOUSLY
MOIST ENVIRONMENT...HAS YIELDED EFFICIENT RAINFALL WITH RADAR
ESTIMATES BELIEVABLE AT 3-4 INCHES LOCALLY.

THROUGH EARLY EVENING HEAVY RAIN MAY CONTINUE IN AREAS ALREADY
HARD HIT AT THE LEADING EDGE OF THE MCS IN NY/CT. THE RAP RUNS
HAVE BEEN CONSISTENT IN TAKING A WAVE OF MID LEVEL ASCENT
NORTHEAST INTO PARTS OF NORTHERN NEW ENGLAND THROUGH 02Z. THE RAP
IS ALSO MORE AGGRESSIVE THAN OTHER MODELS IN PRODUCING QPF OVER
NH/ME...WHICH MAKES SOME SENSE GIVEN THE PRESENCE OF SFC BASED
CAPE STILL 1000 J/KG OR MORE. POTENTIAL FOR HIGHER END FLASH
FLOODING SHOULD BE LESS IN NH/ME...WHERE STORM MOTIONS ARE
SLIGHTLY FASTER AND INSTABILITY WILL BE WANING. IN FACT...THE WARM
SECTOR WAS BEING NARROWED BY A SEA BREEZE NOTED TO HAVE PASSED
THROUGH KGYX RECENTLY. STILL...EFFICIENT RAIN PROCESS COULD YIELD
A QUICK 1.5 INCHES FROM THE HEAVIEST CELLS...WHICH WOULD MEET 1-HR
FLASH FLOOD GUIDANCE.

BURKE

ATTN...WFO...CAR...GYX...BOX...BTV...OKX...ALY...BGM...

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

LAT...LON   43677041 44786886 45106823 45386767 45676783 45536897
            44777064 43697268 42847383 41967490 41387453 41137359
            41467264 42547124 43677041