MESOSCALE PRECIPITATION DISCUSSION 0425
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1039 AM EDT THU OCT 16 2014
 
AREAS AFFECTED...EXTREME SOUTHEAST NY...SOUTHERN VT...SOUTHERN
NH...CT...RI...MA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 161430Z - 162030Z
 
SUMMARY...SIGNIFICANT RAINS ARE EXPECTED THE NEXT SEVERAL HOURS
OVER SOUTHERN NEW ENGLAND...WITH POTENTIAL FOR FLASH FLOODING.

DISCUSSION...THE LATEST IR/WV SAT IMAGERY SHOWS A DEEP PLUME OF
MOISTURE WITH A TROPICAL CONNECTION ORIENTED NW/SE THAT EXTENDS
FROM SOUTHERN NEW ENGLAND AND WELL OFFSHORE IN BETWEEN THE EAST
COAST AND BERMUDA. NUMEROUS CLUSTERS OF COLD-TOPPED CONVECTION ARE
IN EMBEDDED WITHIN THE PLUME ITSELF...AND ALL OF THIS IS ALONG AND
JUST AHEAD OF A STRONG COLD FRONT AND DEEP LAYER TROUGH MOVING
THROUGH THE EASTERN U.S. ATTM.

THIS ATMOSPHERIC RIVER OF MOISTURE CONTAINS PWAT VALUES OF 1.8 TO
2.0 INCHES BASED ON THE LATEST GOES-SOUNDER IMAGERY AND IT IS
EXPECTED THAT DEEP MOISTURE/CONVECTIVE PLUME WILL AIM AND ORIENT
ITSELF FOR A NUMBER OF HOURS INTO SOUTHERN NEW ENGLAND...WHILE
GRADUALLY PIVOTING NORTHEAST UP INTO PORTIONS OF NORTHERN AND
EASTERN NEW ENGLAND THIS AFTERNOON. THE MOISTURE TRANSPORT WILL BE
AIDED BY A ROBUST LOW LVL JET OF 40 TO 50 KTS.

RADAR IMAGERY SHOWS IMPRESSIVE CLUSTERS OF VERY HEAVY SHWRS/TSTMS
NOW COMING ACROSS LONG ISLAND AND MOVING INTO MUCH OF CT AND THIS
ACTIVITY WILL EXPAND NWD INTO MUCH OF MA AND RH OVER THE NEXT
COUPLE OF HOURS. DEEP LAYER UNIDIRECTIONAL FLOW WILL FOSTER A
SIGNIFICANT RISK OF HEAVY RAIN THAT WILL TRAIN OVER THE SAME AREA.
RAINFALL RATES OF 1 TO 2 INCHES/HR ARE EXPECTED...AND WITH THE
PERSISTENT ATLANTIC FETCH...VERY HVY RAINFALL TOTALS CANNOT BE
RULED OUT. OROGRAPHICS WILL PLAY A ROLE IN LOCALLY ENHANCING
RAINFALL RATES.

THE 12Z HRRR SEEMS TO HAVE A REASONABLE HANDLE ON THE CONVECTIVE
AXIS AND DEEP MOISTURE FEED...AND IT FAVORS THE IDEA OF TRAINING
CONVECTION. EXPECT RAINFALL AMTS OF 2 TO 4 INCHES AT LEAST
LOCALLY...WITH ISOLD HEAVIER TOTALS. THIS MAY RESULT IN AREAS OF
FLASH FLOODING.

ORRISON

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

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

LAT...LON   43277312 43277134 41427102 40617167 40677289 
            41747335