MESOSCALE PRECIPITATION DISCUSSION 0922
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
114 AM EDT MON OCT 30 2017

AREAS AFFECTED...RI...EASTERN MA...NH...WESTERN ME...SOUTHERN VT

CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY

VALID 300515Z - 301115Z

SUMMARY...EXTREME MOISTURE FLUX/OROGRAPHIC ASCENT ALONG S
GREEN/WHITE/BLUE MTN RANGES MAY LEAD TO HOURLY RAIN RATES IN
EXCESS OF 1.0" FOR 2-3 HOURS LEADING TO FLOODING WITH POSSIBLE
FLASH FLOODING CONDITIONS THROUGH 12Z. 

DISCUSSION...GOES-16 IR/WV SUITE DEPICTS HIGHLY DYNAMIC AND
RAPIDLY DEEPENING CYCLONE ACROSS THE LOWER HUDSON RIVER VALLEY
WITH IDEAL DUAL JET STRUCTURES AND STRONG BRIGHTNESS TEMPERATURE
GRADIENTS IN WV TO INDICATE SUCH.  BLENDED TPW ANALYSIS ALSO SHOWS
A 225-250 NMI WIDE PLUME OF 1.5" WITHIN THE WARM CONVEYOR BELT
CENTERED ROUGHLY ALONG 70W.  DUE TO STRONG PRESSURE FALLS LOCAL
ISALLOBARIC ACCELERATION OF 925MB WINDS TO 50KTS GENERALLY FROM
THE SOUTHEAST AND PERPENDICULAR TO THE TERRAIN (BEST ALONG THE
WHITES/BLUES) WILL BE STEADILY INCREASING WITH THE APPROACH OF THE
INFLECTION ALONG THE WARM CONVEYOR BELT.

THE 3.9UM SWIR DEPICTS THIS INFLECTION NEAR 37.6N 71.1W PROVIDING
ADDITIONAL STRENGTHENING AND TIGHTENING OF CONVERGENCE MAINLY
NORTHEAST OF THE CIRCULATION.  THIS RESPONSE IS ALREADY
MANIFESTING WITH GROWING COOLING 10.3UM IR TOPS TO -65C WITH
OCCASIONAL OVERSHOOTING TOPS NEAR -70C.
SOME INSTABILITY IS AVAILABLE OVER THE OCEAN WITH MUCAPES TO
100-250 J/KG MAXIMIZING NEAR THE SFC INFLECTION AROUND 500-750
J/KG TO SUPPORT SHALLOW WARM CLOUD PROCESS CONVECTION.  CELL
MOTIONS ARE  PROGRESSIVE ENOUGH TO REDUCE DURATION FOR SIGNIFICANT
TOTALS THOUGH THERE IS A POSSIBILITY OF THE QUICK BURST RATES UP
TO 1.75"/HR TO ALLOW FOR A STRIPE OF 1-2" TOTALS ACROSS RI/EASTERN
MA BEFORE MOVING TOO FAR AWAY FROM THE INSTABILITY SOURCE OF THE
OCEAN.  THIS QUICK BURST MAY POSE AT LEAST A LOCALIZED THREAT FOR
URBAN FLOODING THROUGH 09Z. 

WITHIN THE HIGHER TERRAIN WITH THE APPROACH OF THE WAVE...OVERALL
FLOW WILL BACK SLIGHTLY THROUGH 09-10Z (INTO SE MA/GULF OF ME PER
CURRENT EXTRAPOLATION) AND INCREASE TO 60-75KTS AT 925MB INTO
TOPOGRAPHY WITH 1.25-1.5" AVAILABLE MOISTURE. THIS IS WELL OVER
3-4 STANDARD DEVIATIONS FROM THE MEAN AND SHOULD ALLOW FOR RATES
FROM .75"/HR INCREASE TO MAXIMA NEAR 1.25" FROM
08-12Z...SUPPORTING TOTALS (ALONG THE SOUTHEAST/EASTERN FLANKS OF
THE PRESIDENTIAL PEAKS UP TO 3-4" THROUGH 12Z WITH 2-3" POSSIBLE
FROM THE WESTERN WHITES TO THE CENTRAL BLUE MTN RANGE IN MAINE. 
THESE RATES AND COMPLEX NARROW FUNNELING CHANNELS WILL SUPPORT
FLOODING WITH FLASHY CONDITIONS LIKELY AT TIMES THROUGH 12Z. 

GALLINA

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

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

LAT...LON   46226935 45946865 45206921 44217014 43327056
            42367050 41806993 41217000 41097139 41127167
            42257193 42697285 43517289 44597176 45467077
            45987019