MESOSCALE PRECIPITATION DISCUSSION 0177
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
337 PM EDT FRI JUL 04 2014
 
AREAS AFFECTED...EASTERN LONG ISLAND AND SOUTHEAST NEW ENGLAND 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 041936Z - 050036Z
 
SUMMARY...THUNDERSTORMS WITH INCREASING RAINFALL RATES ARE
EXPECTED ACROSS EASTERN LONG ISLAND AND SOUTHEAST NEW ENGLAND,
WITH 3" AN HOUR RATES POSSIBLE.  CONSIDERING THE RAINFALL RECEIVED
SO FAR TODAY, NUMEROUS INSTANCES OF FLASH FLOODING ARE EXPECTED.

DISCUSSION...HURRICANE ARTHUR CONTINUES MOVING NORTHEAST TOWARDS
THE REGION.  WHILE A SYNOPTIC SCALE FRONTAL BOUNDARY LIES TO ITS
WEST AND NORTH, A COASTAL FRONT IS FOCUSING THUNDERSTORM ACTIVITY
WITH RAINFALL RATES OF 1" AN HOUR.  PRECIPITABLE WATER VALUES NEAR
2" CONTINUE ACROSS THE REGION, AND RECENT RADAR IMAGERY SHOWS
BANDS OF THUNDERSTORMS WITH INCREASING RAINFALL RATES JUST
OFFSHORE LONG ISLAND AND SOUTHERN NEW ENGLAND.

THE 12Z ARW INDICATES THAT CAPES SHOULD RISE ABOVE 1000 J/KG AS
THE RAP GUIDANCE INDICATES THAT 850 HPA INFLOW RAMPS UP OVER THE
NEXT SEVERAL HOURS TO GALE-FORCE.  THE CRITERIA FOR THE WET
MULTI-CELL ENVIRONMENT SHOULD BE REACHED AROUND 21Z.  THE SYNOPTIC
SCALE FRONT IS EXPECTED TO PHASE WITH THE COASTAL FRONT OVER THE
NEXT SEVERAL HOURS, WHICH SHOULD INCREASE SURFACE CONVERGENCE. 
RAINFALL RATES SHOULD APPROACH 3" AN HOUR IN STRONGER STORMS.  THE
CURRENT MESOSCALE GUIDANCE APPEARS TOO LIGHT WITH PRECIPITATION
TOTALS IN THIS REGION, ALL THINGS CONSIDERED.  LOCAL AMOUNTS OF
3-5" LOCALLY DURING THIS PERIOD SHOULD CAUSE NUMEROUS INSTANCES OF
FLASH FLOODING.

ROTH

ATTN...WFO...BOX...OKX...

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

LAT...LON   42177016 41876986 41556993 41547010 41607019 41487053
            41437044 41357038 41337016 41407003 41336990 41196994
            41197028 41297055 41257086 41417112 41347137 41107157
            40867225 41067240 41897172 42497112 42787075 42707053
            42507059 42367084 42177061 41937045 41967027 42127032
            42157027 42177016