Quantitative Precipitation Forecast
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061
FOUS30 KWBC 220817
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
416 AM EDT TUE AUG 22 2017

...VALID 12Z TUE AUG 22 2017 - 12Z WED AUG 23 2017...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 N BGR 15 SSW PWM 10 ENE ORH 10 NE TTN 20 ESE UNV 20 SE EKN
10 NW BLF 40 SW CSV 30 NNE ELD 15 N MWL 35 E HOB 35 NNW ROW
20 SSW SKX 15 NE RTN 30 SSW DHT 30 S GAG 30 ESE PNC 20 NNE AIZ
10 NNE LWV 15 SSE CTZR CMHB 60 ENE CWHV 15 N BGR.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
10 SE SRC 25 E M89 15 NNE GLE 15 NNE LBB 40 SSW AMA 25 NE CSM
20 NW MKO 35 S FLP 10 SE SRC.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 NE LEX 15 SSE ZZV 15 NW ERI 30 NNW ROC 10 ESE CTWN 40 E CYSC
25 N WVL 10 E CON 30 S PSF 25 SSW MSV 30 SE ELM 40 NE FIG
15 S MGW 25 ESE JKL 30 NNE SME 25 NE LEX.


...EASTERN OHIO VALLEY AND LOWER GREAT LAKES INTO THE NORTHEAST...


VIGOROUS NORTHERN STREAM SHORTWAVE PIVOTING ACROSS THE UPPER MS
VALLEY AND GREAT LAKES THIS PERIOD WILL ALLOW FOR TROUGH
AMPLIFICATION/HEIGHT FALLS ACROSS THE NORTHEAST
SECTOR...ULTIMATELY LEADING TOWARD A CUTOFF MID/UPPER LOW INTO
SOUTHERN QUEBEC BY THE END OF THE PERIOD (12Z WED). GIVEN THE
DEGREE/DEPTH OF SYNOPTIC SCALE FORCING...THE MODELS ARE FAIRLY
WELL CLUSTERED WITH THE SURFACE LOW TRACK INTO SOUTHEAST
ONTARIO-SOUTHERN QUEBEC ALONG WITH THE ASSOCIATED ELONGATED COLD
FRONT...THOUGH SLIGHT TIMING DIFFERENCES REMAIN WITH THE
PROGRESSION OF PRE-FRONTAL CONVECTION. BASED ON THE LATEST MODEL
TRENDS...PARTICULARLY WITH THE ENSEMBLE OF HIGH-RES CAMS AND
PARALLEL VERSIONS...WPC INCREASED QPF TOTALS ACROSS PORTIONS OF
THE LOWER AND EASTERN OH VALLEY INTO THE NORTHEAST...ESPECIALLY
FROM EASTERN KY...WESTERN PA...AND MUCH OF NY INTO NORTHERN NEW
ENGLAND. LOW-LEVEL FRONTOGENESIS AHEAD OF THE TROUGH WILL BE MOST
FAVORABLE OVER THESE AREAS...WHILE COUPLING WITH AN IMPRESSIVE
PRE-FRONTAL THERMODYNAMIC ENVIRONMENT AS MIXED LAYER CAPES PEAK
BETWEEN 1000-2000 J/KG ALONG WITH PWs OF 1.75-2.00 INCHES. THE
HEAVY RAINFALL SIGNAL IS FURTHER SUPPORTED BY THE UPTICK IN
LOW-LEVEL MOISTURE POOLING (850 MB SOUTHWESTERLY FLOW 45-55+ KTS
PER THE MODELS) AND ATTENDANT NOTEWORTHY MOISTURE FLUX ANOMALIES
(4-5 STANDARD DEVIATIONS ABOVE NORMAL).

THE PROGRESSIVE NATURE OF THE FRONT REMAINS THE MAIN INHIBITOR TO
THE EXCESSIVE RAINFALL POTENTIAL. HOWEVER...THE AFOREMENTIONED
UPTICK IN SOUTHWESTERLY INFLOW LATER THIS AFTERNOON-EVENING
(UPWIND PROPAGATION) MAY ALLOW FOR SOME CELL
TRAINING...PARTICULARLY OVER WESTERN PA INTO WESTERN-UPSTATE NY
AND NORTHERN VT-NH. A "SLIGHT" RISK WILL BE NOTED ACROSS THESE
AREAS AND INTO EASTERN PORTIONS OF THE OH VALLEY (WITH THE HIGHER
ANTECEDENT SOIL MOISTURE/LOWER FFG) IN THE NEW DAY 1 EXCESSIVE
RAINFALL OUTLOOK (ERO).


...PORTIONS OF THE SOUTHERN PLAINS AND LOWER MISSISSIPPI VALLEY...

ACROSS THE SOUTHERN PLAINS (PARTICULARLY ALONG AND JUST NORTH OF
THE RED RIVER) INTO CENTRAL AR...THE MODELS CONTINUE TO DEPICT A
SIGNAL FOR HEAVY RAINFALL ALONG AND SOUTH OF THE FRONT WHICH WILL
BECOME DRAPED MORE OR LESS IN A W-E FASHION. GIVEN THE FRONTAL
ORIENTATION AND ANTICIPATED LOW-LEVEL AND MEAN LAYER
FLOW...CHANCES FOR CELL TRAINING ARE HEIGHTENED OVER THIS REGION
AS NOTED BY THE WEAK MBEs/CORFIDI VECTORS LATE TUE INTO EARLY WED
(5 KTS OR LESS). WPC WILL INCLUDE A "SLIGHT" RISK OVER THIS REGION
AS WELL IN THE DAY 1 ERO.

HURLEY
$$





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