Quantitative Precipitation Forecast
Issued by NWS

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000
FOUS30 KWBC 190101
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
900 PM EDT FRI AUG 18 2017

...VALID 01Z SAT AUG 19 2017 - 12Z SAT AUG 19 2017...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 SW MMCS 30 E MMCS 30 WNW GDP 25 S CNM 10 N INK 25 SE INK
20 NW FST 45 ESE E38 75 SW 6R6 105 S E38 90 E MMCU.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
100 ENE DAB 35 E DAB 30 SSE ISM 35 E APF 20 SW APF 15 SW SRQ
70 SSW CTY 25 SE AAF 30 SSE DTS 30 NNW KMIS 30 WNW MSY
30 NNE LFT 20 NNW ACP 20 WNW IER 25 W SHV DUA 20 ESE HBR
25 SSE PPA 25 S GUY 35 NE LBL 15 NE EWK 30 SSE BIE 20 ENE LNK
10 NW RDK 35 ENE MCI 15 SE JEF 35 S UNO 10 ENE SGT 30 NNE GLH
45 WNW MEI 15 NW GZH 10 E DHN 20 NNW MGR 10 S SSI 45 E CHS
15 W SUT 15 SSE CTZ 45J HBI 15 ENE DAN 25 ESE HSP 20 S OKV
20 ENE W99 15 NNW MKJ 35 N LNP 30 E PKB 15 ENE FIG 15 ESE BGM
10 NNE RME SLK CWIZ 10 NNE CYSC 25 SE GNR 30 NNW CWSS
25 ESE CWPE 20 SW CYQI.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
35 SSE WWD 10 SSW OXB MFV 10 NE RIC 15 E LKU 10 NE IAD
25 NNW ILG 15 ENE FWN DDH 10 WSW IZG 20 NW RKD 70 SE RKD OWD
10 SW HTO.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 E GMJ 20 NE JSV 15 SW MKO 20 W RVS 20 W BVO 15 NW CNU
45 SSE OJC 45 NW SGF 20 E GMJ.


01Z UPDATE...

FURTHER ADJUSTMENTS WERE MADE TO THE PREVIOUS OUTLOOK BASED UPON
CURRENT/RADAR SATELLITE TRENDS AND RECENT RUNS OF THE HRRR AND
ENSEMBLE GUIDANCE...INCLUDING THE NBM.  AS CONVECTION CONTINUES TO
DIMINISH WITH THE LOSS OF AFTERNOON HEATING...REMOVED FL AND THE
CENTRAL GULF COAST REGION FROM THE MARGINAL RISK.  ACROSS THE MID
ATLANTIC...REMOVED MUCH OF THE WESTERN EXTENT OF THE PREVIOUS
OUTLOOK.  HEAVY RAIN/FLASH FLOODING THREAT IS EXPECTED TO BE
MAINLY SHORT-LIVED AND CONFINED TO THE IMMEDIATE COASTAL REGIONS
AS THE ONGOING LINE OF CONVECTION PUSHES THROUGH OVER THE NEXT
COUPLE OF HOURS.  ALONG THE MS VALLEY...EXTENDED THE MARGINAL RISK
FURTHER TO THE NORTH INTO THE UPPER MS VALLEY...COVERING PORTIONS
OF SOUTHERN MN...IA AND WESTERN IL.  LIMITED MOISTURE AND THE
PROGRESSIVE NATURE OF STORMS DEVELOPING ACROSS THE REGION IS
EXPECTED TO HAMPER THE THREAT FOR WIDESPREAD RUNOFF
CONCERNS...HOWEVER BRIEF HEAVY RAINFALL RATES AND/OR CELL TRAINING
MAY POSE A LOCALIZED THREAT.  FURTHER TO THE SOUTH...MAINTAINED
AND SHIFTED SOUTHEAST THE SLIGHT RISK CENTERED ACROSS OZARK
REGION.  SLOW MOVING/BACK-BUILDING STORMS HAVE CONTINUED INTO THE
EVENING HOURS ACROSS THE REGION...RESULTING IN SOME LOCALLY HEAVY
TOTALS.  HOWEVER RECENT RADAR RETURNS SHOW RAINFALL RATES
BEGINNING DIMINISH AND SATELLITE SHOWS WARMING CLOUD
TOPS...SUGGESTING ANY ADDITIONAL EXCESSIVE RAINFALL THREAT MAY BE
SHORT-LIVED.

PEREIRA

15Z UPDATE...

WPC MADE VERY MINOR ADJUSTMENTS TO THE PREVIOUS EXCESSIVE RAINFALL
FORECAST. THIS INCLUDES PULLING BACK THE SLIGHT THREAT FARTHER
WEST INTO THE DC METRO AREA AND THE MARGINAL BACK WEST INTO THE
MID-ATL TO WV. ALSO EXTENDED THE MARGINAL THREAT A BIT FURTHER
NORTH INTO THE CENTRAL PLAINS BASED ON LATEST GUIDANCE. OVERALL
WPC DID NOT WANT TO MAKE LARGE ADJUSTMENTS WITH DIURNAL HEATING
EXPECTED AND INCREASE INSTABILITY.

MUSHER


...MID ATLANTIC TO THE NORTHEAST STATES...

MAINTAINED THE SLIGHT RISK PRETTY MUCH IN PLACE WHERE IT WAS AS A
DAY 2 FORECAST.  THE AREA AHEAD OF AN APPROACHING COLD FRONT HAS
AN ANOMALOUS AMOUNT OF LOW LEVEL MOISTURE...ALREADY IN POSITION AS
AN AREA OF HEIGHT FALLS APPROACHES FROM THE GREAT LAKES REGION.
IN ADDITION...THE APPROACH OF A SURFACE COLD FRONT WILL ALSO FOCUS
THE ACTIVITY.  WITH NEARLY 2 INCHES OF PRECIPITABLE WATER IN
PLACE...ABOUT 2 STANDARDIZED ANOMALIES ABOVE
CLIMATOLOGY...CONVECTION SHOULD BE EFFICIENT PRODUCERS.  THINKING
IS THAT THE BEST CHANCES FOR HEAVY RAINFALL ACROSS THE MID
ATLANTIC WILL BE EAST OF THE I 95 CORRIDOR...WHILE IN THE
NORTHEAST SOME MODELS ARE HINTING THAT THE HEAVY RAIN MAY FORM OFF
SHORE AND NOT GET DRAWN INLAND.  THE SLIGHT RISK CONVEYS THE IDEA
THAT HEAVY RAINFALL IS POSSIBLE IN
THIS AREA WHILE SOME QUESTIONS REMAIN...ESPECIALLY WITH RESPECT TO
PLACEMENT.

...CENTRAL PLAINS...

MODELS STILL DEPICT CONVECTION DEVELOPING OVER PARTS OF THE
CENTRAL PLAIN THIS AFTERNOON ALONG AN AXIS OF HIGH PRECIPITABLE
WATER VALUES.  THE MODELS HAVE BACKED OFF THEIR PRESENTATION OF
RAINFALL AMOUNTS...BUT WITH THE ATMOSPHERE BEING SOME 2.5
STANDARDIZED ANOMALIES ABOVE NORMAL...AND THE RIGHT ENTRANCE
REGION OF AN UPPER LEVEL JET SWEEPING OVER THE AREA AT THE RIGHT
TIME OF DAY...WE MAINTAINED A SLIGHT RISK OVER PARTS OF OK WITH A
FAIRLY WIDE MARGINAL RISK AREA SURROUNDING THAT.  ALSO PULLED THE
MARGINAL RISK BACK WEST IN RESPONSE TO LOCATION OF CONVECTION
WHICH FIRED UP OVER NIGHT ACROSS PARTS OF WESTERN OK.  THAT SHOULD
BE A SHORT TERM CONCERN.

GRAPHICS AVAILABLE ON THE WEB AT WWW.WPC.NCEP.NOAA.GOV

BANN

$$





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