Quantitative Precipitation Forecast
Issued by NWS

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FOUS30 KWBC 221907
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
306 PM EDT FRI AUG 22 2014

...VALID 18Z FRI AUG 22 2014 - 00Z SUN AUG 24 2014...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 SSW C09 VPZ 15 WNW ASW ASW 15 NW FWA 25 ESE FWA 20 W AOH
20 SW AOH 25 NNW DAY 35 WNW DAY 25 ESE MIE 25 SSE MIE 25 E GEZ
15 NE BAK 20 ENE BMG 20 SE HUF 25 SSW PRG 15 SE DEC SPI
10 ENE UIN 20 SW EOK 30 ESE LWD 20 E ICL 15 NW RDK 15 NE CBF
15 SW DNS 15 NNE DNS 15 NNE CIN 15 NNE BNW 35 E TNU 15 SSE IOW
15 E MLI 15 SSW C09.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 NW CWVN 10 ENE CWAQ 30 WSW KD50 25 N ISN 10 SSW K08D
10 NNE N60 35 SW K46D 35 SW JMS 45 NW ABR 30 SW ABR 15 WNW HON
30 ENE 9V9 20 S 9V9 15 W ICR 50 SSE PHP 40 NNE IEN 15 E RAP
40 NNW RCA 55 W 2WX 65 NNE SHR 15 E BIL 45 W BIL 25 E LVM
25 SW LVM 40 SSW BZN DLN 30 WNW BTM 35 N 3DU 35 SE GPI
30 WSW 8S0 10 ENE CXDB 10 N CWOE 25 WSW CWEH 25 NW CWVN.


NORTHERN ROCKIES/NORTHERN HIGH PLAINS

A BROAD SLIGHT RISK AREA MAINTAINED FROM THE NORTHERN ROCKIES INTO
THE NORTHERN HIGH PLAINS THIS PERIOD.  THERE IS GOOD MASS FIELD
AGREEMENT IN THE MODELS WITH THE UNSEASONABLY STRONG PACIFIC
NORTHWEST CLOSED LOW PUSHING INTO THE NORTHERN ROCKIES TONIGHT AND
THE NORTHERN HIGH PLAINS DURING SAT.  ANOMALOUSLY STRONG EASTERLY
LOW LEVEL EASTERLY FLOW AND VERY WELL DEFINED UPPER DIFFLUENCE
EXPECTED FROM THE NORTHERN TO CENTRAL HIGH PLAINS INTO THE
NORTHERN ROCKIES.  THIS WILL SUPPORT WIDESPREAD HEAVY
PRECIPITATION TOTALS FROM THE NORTHERN ROCKIES---EASTWARD INTO THE
NORTHERN HIGH PLAINS--ALONG WITH THE THREAT OF RUNOFF
ISSUES---ESPECIALLY IN THE UPSLOPE REGIONS OF THE NORTHERN ROCKIES
AND WITH ANY CONVECTIVE ELEMENTS FIRING FARTHER EASTWARD INTO THE
NORTHERN HIGH PLAINS.  THERE IS VERY GOOD MODEL AGREEMENT ON THIS
PORTION OF THE HEAVY PRECIPITATION AREA AHEAD OF THE CLOSED LOW
IN THE LATEST GUIDANCE--LEADING TO A HIGH CONFIDENCE FORECAST
ACROSS THESE AREAS.

NORTHERN TO CENTRAL HIGH PLAINS---EASTWARD INTO THE MID MS
VALLEY/MID WEST

THERE ARE BIGGER QPF DIFFERENCES FARTHER EASTWARD INTO PORTIONS OF
THE NORTHERN TO CENTRAL PLAINS TOWARD THE UPPER MS VALLEY AND MID
WEST.  ONE ASPECT IS HOW CONVECTION WILL DEVELOP TONIGHT OVER THE
CENTRAL HIGH PLAINS AND WHETHER IT DOES MOVE ON A MORE NORTHERLY
TRACK AS PER THE ECMWF---SREF MEAN AND UKMET OR TAKES A MORE
EASTERLY TRACK AS PER THE HI RES ARW---NMM--NAM CONEST AND GFS.
THIS MORE EASTERLY TRACK IS FOR CONVECTIVE DEVELOPMENT ALONG THE
WARM FRONT EXTENDING WEST TO EAST WHERE LOW LEVEL SOUTHERLY TO
SOUTH SOUTHWESTERLY FLOW WILL IMPACT TONIGHT.    THERE IS A LOT OF
RUN TO RUN DIFFERENCES HERE ALSO IN THE HI RES GUIDANCE---LEADING
TO OVERALL LOW CONFIDENCE IN HOW THE CONVECTION WILL EVOLVE.  AT
THE MOMENT---WPC QPF LEANED TOWARD THE IDEA OF CONVECTION PUSHING
FARTHER TO THE EAST AS PER THE LATEST HI RES GUIDANCE AND GFS
THROUGH TONIGHT AND THEN RE-DEVELOPING FARTHER TO THE WEST DURING
THE DAY ON SATURDAY CLOSER TO THE UPPER CENTER ACROSS THE WESTERN
PORTIONS OF THE NORTHERN PLAINS.  THIS IS FOR OUR OVERALL HIGHER
CONFIDENCE IN THE HI RES GUIDANCE WITH ORGANIZED CONVECTIVE
DEVELOPMENT--ALTHOUGH NOT VERY CONFIDENT OVERALL WITH THIS
EVOLUTION.  WITH RECENT HEAVY RAINS OVER PORTIONS OF THE MID MS
VALLEY AND MID WEST---ANY ADDITIONAL CONVECTION THAT DOES PUSH
EASTWARD MAY MOVE OVER AREAS THAT RECEIVED HEAVY PRECIPITATION
EARLIER TODAY AND MAY RESULT IN ADDITIONAL RUNOFF ISSUES.  FOR
THAT REASON A SLIGHT RISK AREA WAS DEPICTED ACROSS THESE
AREAS---BUT ALSO FOR AREAS FARTHER TO THE WEST FROM CENTRAL SD
INTO ND WHERE THERE IS MORE MODEL SPREAD,

NORTHEAST CO

NO CHANGES MADE TO THE PREVIOUS SLIGHT RISK AREA OVER NORTHEAST
CO.  CONVECTION CONTINUES TO ENHANCE THIS AFTERNOON AS SHORTWAVE
ENERGY PUSHES NORTHEASTWARD OUT OF THE SOUTHWESTERN U.S. UPPER
TROF.  FAVORABLE UPPER DIFFLUENCE AHEAD OF THESE VORTS AND IN THE
RIGHT ENTRANCE REGION
OF THE UPPER JET FARTHER TO THE NORTHEAST OVER THE CENTRAL AND
NORTHERN PLAINS WILL SUPPORT CONTINUED ORGANIZED CONVECTION AND
HEAVY RAINS IN AN AXIS OF MUCH ABOVE AVERAGE PW VALUES--- 2 TO
2.5+ STANDARD DEVIATIONS ABOVE THE MEAN--FORECAST ACROSS THIS
REGION. ISOLATED SHORT TERM PRECIP TOTALS OF 1-2"+ POSSIBLE.

CENTRAL APPALACHIANS

A SLIGHT RISK AREA WAS MAINTAINED OVER PORTIONS OF THE CENTRAL
APPALACHIANS WHERE FFG VALUES ARE RELATIVELY LOW. THE EASTERN
EXTENT OF THE FRONTAL BOUNDARY AFFECTING THE CENTRAL PORTION OF
THE NATION WILL STRETCH EASTWARD FROM THE MID MS VALLEY---THROUGH
THE OH VALLEY AND INTO THE MID ATLANTIC THIS PERIOD.  WITH THE
AXIS OF ABOVE AVERAGE PW VALUES PERSISTING IN THE VICINITY OF THIS
BOUNDARY THROUGH THIS PERIOD---THE CURRENT SHOWERY PATTERN WILL
CONTINUE.  NOT A LOT OF CONFIDENCE WITH QPF DETAILS IN THIS
PATTERN---BUT GIVEN THE LOW FFG VALUES AND HIGH PW
VALUES--ISOLATED RUNOFF ISSUES WILL PERSIST OVER PORTIONS OF THE
CENTRAL APPALACHIANS.

ORAVEC
$$




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