MESOSCALE PRECIPITATION DISCUSSION 0626
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
730 AM EDT SAT AUG 05 2017

AREAS AFFECTED...E UPSTATE NY...E LONG
ISLAND...CT...RI...VT...NH...MA

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

VALID 051130Z - 051700Z

SUMMARY...FLASH FLOODING THREAT SHIFTS FROM SOUTHERN NEW ENGLAND
TO DEVELOPMENT ALONG COLD FRONT INTO N/CENT NEW ENGLAND BY
MID-MORNING

DISCUSSION... NEAR TERM....LI/CT/MA/RI... WARM CONVEYOR BELT IN
ADVANCE OF MAIN HEIGHT FALLS/COLD FRONT HAS PUMPED AMPLE MOISTURE
AND INSTABILITY NORTH ACROSS EASTERN LI INTO CT/RI WITH TEMPS/TDS
IN THE LOWER TO MID 70S SUPPORTING TPWS BETWEEN 1.75-2" AND CAPES
IN THE 500-1000 J/KG RANGE.  CONVECTIVE CLUSTER FROM OVERNIGHT HAS
PRESSES OUTFLOW BOUNDARY FURTHER EAST FURTHER ENHANCING MST
CONVERGENCE ALONG AND EAST OF IT...WHERE PRECURSORY SHALLOW
CONVECTION HAS BROKEN OUT ACROSS CENTRAL MA/CT AND E LI WITH
MODEST WARM CLOUD RAINFALL PROCESSES BEFORE THE STRONGER DOWNPOURS
WITH CONVECTION ALONG THE OUTFLOW.

HI-RES CAMS HAVE BEEN STRUGGLING WITH TIMING OF THIS EVOLUTION
GENERALLY ABOUT 1-1.5 HOURS TOO SLOW...YET THERE IS SOME
SUGGESTION WITH SOME CLEARING IN
MID-MORNING...INSTABILITY/MOISTURE MAY RECHARGE SUFFICIENTLY FOR
AN ADDITIONAL ROUND OF DEVELOPMENT PARTICULARITY ACROSS E MA/CT. 
THIS WOULD BE ASSOCIATED WITH A SUBTLE SHORTWAVE WITHIN THE WARM
CONVEYOR (PER GOES-WV) LIFTING NORTH OUT OF EASTERN PA/S NJ AT
THIS TIME.  THE ORIENTATION OF THIS WAVE WITH THE APPROACH OF THE
SURFACE COLD FRONT MAY ACT AS A ANCHOR/PIVOT POINT THAT MAY SLOW
FORWARD PROPAGATION AND ALLOW FOR A LOCALIZED AREA OF INCREASED
TOTALS IN CENTRAL MA/CT BY MID-MORNING...WITH RAIN RATES OF
1.75-2"/HR THERE IS A THREAT FOR LOCALIZED TOTALS AOA 2-3" POSING
FLASH FLOOD RISK.

FURTHER NORTH...E NY/VT/E NH...
GOES-WV LOOP INDICATES STRONGLY CURVED MID-LEVEL TROF CROSSING LK
ONTARIO/S QUEBEC WITH NE-SW ORIENTATION TO THE MEAN MID-LEVEL FLOW
TO BECOME ORIENTED FAIRLY CLOSE TO THE COLD FRONT...SLOWING
EASTWARD PROGRESS AND SUPPORTING INCREASED TRAINING ENVIRONMENT. 
CURRENTLY WEAK SHOWERS ARE DEVELOPING ALONG THE FRONT IN E NY...ON
LIMITED ELEVATED INSTABILITY.  GUIDANCE SUGGESTS A BIT OF
CLEARING/INCREASED INSTABILITY DEVELOPING TOWARD LATE
MORNING/LOCAL NOON...THOUGH WEAK SHORTWAVE RIDGING IS APPROACHING
WITH WEAK BAROCLINIC LEAF SEGMENT THAT MAY DELAY THIS CLEARING.

STILL STRONG FORCING/AMPLE MOISTURE AND THE TRAINING PROFILE ALONG
WITH LOCALIZED WET GROUND CONDITIONS FROM RECENT LATE WEEK'S WORTH
OF SLOW MOVING CONVECTION MAY STILL POSE SOME LOCALIZED EARLY
MORNING FF THREAT ACROSS E NY INTO VT BEFORE BREAKING OUT A BIT
GREATER IN INTENSITY/COVERAGE TOWARD EARLY AFTERNOON.  WILL
CONTINUE TO MONITOR AND REASSESS AS THAT TIME APPROACHES. 

GALLINA

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

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

LAT...LON   45357147 45327107 43927136 42967140 42397084
            41437117 40927171 40767212 40597331 41417335
            41987352 42937421 44637354 45077305 45147224