Quantitative Precipitation Forecast
Issued by NWS

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732
FOUS30 KWBC 120742
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
241 AM EST FRI JAN 12 2018

...VALID 12Z FRI JAN 12 2018 - 12Z SAT JAN 13 2018...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 ESE LNS 10 SW RDG 10 NNW CXY 10 WSW HGR 25 NW SHD 10 SW LWB
25 N I16 ZZV 20 NW YNG BUF 10 ESE CTCK 20 S CWJB 35 WNW PQI
15 NNW CWZF 25 ESE CWPE 25 WNW CYQI.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
45 E BLM 15 ESE BLM 10 N NEL 15 ENE TTN MMU 10 S SWF BAF ORH
OWD 10 S PYM 20 WSW MVY 20 SSE BID.


..EASTERN OHIO VALLEY / NORTHERN APPALACHIANS / NORTHEAST...

THE FULL-LATITUDE EASTERN U.S. MID-UPPER LEVEL TROUGH, WITH
DISTINCTIVE NORTHERN AND SOUTHERN STREAM COMPONENTS/SHORT WAVES,
WILL GRADUALLY PUSH EAST OF THE MISSISSIPPI VALLEY TODAY AND
TOWARD THE EASTERN SEABOARD DURING DAY 1. THE
STRENGTH/AMPLIFICATION OF THE SOUTHERN STREAM SYSTEM IS ALLOWING
FOR HIGHLY ANOMALOUS DEEP-LAYER MOISTURE FLUX DOWNSTREAM ACROSS
MUCH OF THE EASTERN SEABOARD FROM THE MID ATLANTIC THROUGH THE
NORTHEAST -- WITH THE ANOMALIES HIGHEST ACROSS THE NORTHERN
LATITUDES. PER THE OBSERVED 00 UTC AND FORECAST SOUNDINGS AHEAD OF
THE FRONT, RECORD OR NEAR RECORD PW VALUES ARE ANTICIPATED BASED
ON THE SPC SOUNDING CLIMATOLOGY DATABASE, AGAIN ESPECIALLY OVER
THE NORTHEAST WHERE PWs WILL PEAK BETWEEN 4-5+ STANDARD DEVIATIONS
ABOVE NORMAL. MOREOVER, THE ELONGATED WARM CONVEYOR BELT WITH
MOISTURE CONFLUENCE FROM BOTH THE GULF OF MEXICO AND WESTERN
ATLANTIC WILL LEAD TO OPTIMAL 850-700 MB MOISTURE TRANSPORT AND
FLUX ANOMALIES (ALSO +4 TO +5 OR MORE STANDARD DEVIATIONS PER THE
SREF AND GEFS MEAN), COINCIDING WITH THE ROBUST LOW-LEVEL
SOUTHERLY INFLOW ALONG AND AHEAD OF THE FRONT (850 MB WINDS OF
50-60+ KTS ACROSS THE MID ATLANTIC AND NORTHEAST).

ROBUST DYNAMICAL AND THERMODYNAMICAL FORCING WILL RESULT IN HIGHLY
EFFICIENT RAINFALL RATES FOR MID JANUARY, POSSIBLY AIDED BY WEAK
ELEVATED INSTABILITY (MUCAPES ~200-400 J/KG) INTO THE MID ATLANTIC
AND SOUTHERN NEW ENGLAND. PER THE HREF, HIGH PROBABILITIES OF >1
INCH RAINFALL AMOUNTS WITHIN A 3 HOUR PERIOD WILL COME CLOSE TO
(IF NOT EXCEED) THE CURRENT 3 HOURLY FFG VALUES WITHIN PORTIONS OF
THE BROAD DAY 1 EXCESSIVE RAINFALL OUTLOOK AREA FROM THE EASTERN
OH VALLEY AND APPALACHIANS INTO THE NORTHEAST. THIS ALONG WITH THE
MORE RAPID SNOWMELT WILL MAINTAIN A MARGINAL RISK OF EXCESSIVE
RAINFALL (ISOLATED FLASH FLOOD THREAT, AGAIN MITIGATED BY THE LACK
OF DEEP-LAYER CONVECTION AND MORE ROBUST RAINFALL RATES). WILL
ALSO KEEP THE SLIGHT RISK AREA FROM YESTERDAY`S DAY 2 ERO ACROSS
NORTHEAST NJ, NYC, LONG ISLAND, MUCH OF CT, RI, AND SOUTHERN MA
WHERE HIGHER RAINFALL TOTALS (2-4+ INCHES) ARE ANTICIPATED PER A
MULTI HIGH-RES MODEL BLEND.

THIS BROAD SYSTEM WILL GENERATE A LARGE AREA OF WINTRY
PRECIPITATION DURING THE DAY 1 PERIOD. FOR FURTHER DETAILS
REGARDING THE POTENTIAL FOR SNOW AND/OR ICE ACCUMULATIONS, PLEASE
REFER TO THE QPFHSD.

HURLEY
$$





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