Quantitative Precipitation Forecast
Issued by NWS

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FOUS30 KWBC 181406
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1004 AM EDT SUN SEP 18 2016

...VALID 15Z SUN SEP 18 2016 - 12Z MON SEP 19 2016...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 SSE JFK MFV JGG RMN 25 NW FVX 20 SW EHO 15 NNW AHN 10 E VPC
15 NNW 4A9 40 NNE MDQ 35 NW CSV 15 SE SME 10 WNW 3I2 DUJ
20 NE RME 10 N 1P1 25 SW CAFC 25 W CWKG 50 NNE PVC 25 SSE JFK.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
CRW 10 NNW MGW 30 NNW IPT 15 W BGM 10 ENE BGM 35 E BGM
10 WNW MSV 25 SSW MSV 10 S MPO 10 ENE RDG 10 SE THV 10 SW JYO
30 WNW CJR 20 NNE HSP 25 SW LWB 15 SSE 6V3 VJI 15 NW LNP CRW.


15Z UPDATE...

A SLIGHT WWD ADJUSTMENT TO THE MARGINAL RISK AREA WAS MADE TO
PREVIOUS OUTLOOK AREA BASED ON ONGOING RADAR TRENDS INDICATING
SLOW MOVING NE/SW ORIENTED BAND ACRS CNTL TN.
OTHERWISE..CONSECTUTIVE HRRR SIMULATED REFLECTIVITY RUNS SHOW
POTNL FOR ORGANIZED CONVECTIVE BANDING DVLPG ACRS MUCH OF THE
SRN/CNTL APLCNS INTO ERN NY STATE/SRN NEW ENGLAND BY LATER THIS
AFTN/EVENG WHICH WILL LIKELY BE SLOW MOVING LEADING TO POTNL FOR
LOCALIZED RUNOFF ISSUES.

SOUTHERN TO CENTRAL APPALACHIANS---MID ATLANTIC--EASTERN NY STATE
INTO CENTRAL TO SOUTHERN NEW ENGLAND

THE SURFACE FRONTAL BOUNDARY CURRENTLY STRETCHING FROM THE EASTERN
LAKES INTO THE LOWER OH VALLEY AND LOWER MS VALLEY WILL BE
PRESSING SLOWLY EASTWARD THROUGH THE OH VALLEY---TN
VALLEY---SOUTHERN TO CENTRAL APPALACHIANS AND MID ATLANTIC.  PW
VALUES AHEAD OF THIS FRONT EXPECTED TO REMAIN ABOVE AVERAGE---1.5
TO 2+ STANDARD DEVIATIONS ABOVE THE MEAN.  THIS AND FAVORABLE
RIGHT ENTRANCE REGION JET DYNAMICS WILL SUPPORT A BROAD REGION OF
POTENTIALLY HEAVY RAINFALL TOTALS STRETCHING FROM THE SOUTHERN TO
CENTRAL APPALACHIANS---MID ATLANTIC AND INTO EASTERN NY STATE AND
CENTRAL TO SOUTHERN NEW ENGLAND.  THERE IS A VARIETY OF MODEL QPF
SOLUTIONS WITH RESPECT TO THE MAX AXES---LEADING TO LOW CONFIDENCE
WITH THE EXACT DETAILS---BUT HIGHER THAT THERE WILL BE HEAVY
RAINFALL POTENTIAL.  TRAINING OF CELLS IN A SOUTH SOUTHWEST TO
NORTH NORTHEASTERLY DIRECTION POSSIBLE---ESPECIALLY FROM THE
SOUTHERN TO CENTRAL APPALACHIANS INTO THE MID ATLANTIC.  THIS MAY
RESULT IN LOCALIZED RUNOFF ISSUES---EVEN THOUGH FFG VALUES ARE
HIGH FROM THE RECENT DRY WEATHER ACROSS THESE AREAS.  THE WPC QPF
LEANED MORE TOWARD THE IN HOUSE PSEUDO BIAS CORRECTED MEAN TO
MITIGATE THE DIFFERENCES WITH THE QPF AXIS.

ORAVEC/SULLIVAN
$$





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