Quantitative Precipitation Forecast
Issued by NWS

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000
FOUS30 KWBC 170101
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
900 PM EDT WED AUG 16 2017

...VALID 01Z THU AUG 17 2017 - 12Z THU AUG 17 2017...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
GZH 35 SW GZH 35 ENE HBG 20 SSE JAN 35 N HKS 40 SE GWO 20 N NMM
50 W MGM GZH.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
30 SE POF 25 SE FLP 30 E DEQ 10 N PRX 20 W DUA 15 ENE SPS
40 SE MAF 25 N BPG 55 E LBB 15 N CSM 15 NNE PNC 50 SSE OJC
45 N DMO 25 S MXO 10 ENE DEH 15 SSE MKT 25 NW FSD 35 NW ATY FSE
10 NNW INL 40 NW CKC IWD EGV 25 S P75 15 SW HTL 30 NNW GRR RAC
RPJ 15 SSE PNT 15 NNE TAZ 20 SE DEC 10 W EYE 15 WSW BMG 10 N M30
30 SE POF.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 SSE DMO 10 SSE JEF 25 E TBN 20 WNW CGI 10 SSE UNO 35 NE ROG
15 NNW TQH 15 SE SNL 15 SE CHK 30 WNW CHK 10 SSE JWG 25 E PNC
30 E PPF 20 SSE DMO.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 SSE HIB 10 NNW MZH 15 NNW ANE 20 SW LUM 15 S RGK 20 N ULM
15 N PQN 15 NW BKX 8D3 10 SE DTL 20 S FOZ 15 SSE HIB.


0100 UTC UPDATE

MADE SOME FURTHER ADJUSTMENTS TO THE PREVIOUS OUTLOOK BASED ON
RADAR/SATELLITE TRENDS...AS WELL AS RECENT RUNS OF THE HRRR AND
THE ENSEMBLE GUIDANCE...INCLUDING THE NBM.

ACROSS THE UPPER MIDWEST...THIS INCLUDED REMOVING IA FROM THE
OUTLOOK WHILE EXTENDING THE MARGINAL RISK FURTHER EAST ACROSS WI
INTO MI.  WARM ADVECTION PRECIPITATION IS EXPECTED TO LIFT
PROGRESSIVELY ACROSS THE REGION...HOWEVER ANOMALOUS MOISTURE
LIFTING NORTH MAY SUPPORT EFFICIENT RAIN PROCESSES AND HEAVY
RAINFALL RATES...RESULTING IN LOCALLY HEAVY TOTALS.
MEANWHILE...MODEL CONSENSUS CONTINUES TO SHOW ADDITIONAL HEAVY
AMOUNTS WITHIN COMMAHEAD CENTERING TO THE WEST OVER SOUTHWESTERN
MN.  REFER TO WPC MESOSCALE PRECIPITATION DISCUSSION #703 (VALID
THROUGH 0530 UTC) FOR FURTHER DISCUSSION ON THE SHORT-TERM HEAVY
RAINFALL/FLASH FLOODING THREAT ACROSS PORTIONS OF THE REGION.

FURTHER SOUTH...CONVECTION ACROSS WESTERN MO...EASTERN KS AND OK
IS STARTING TO NARROW AND BECOME MORE OUTFLOW DOMINATED.
HOWEVER...LOCALLY HEAVY AMOUNTS ARE STILL POSSIBLE...ESPECIALLY
SHOULD ANY WAVES FORM ALONG THE CONVECTIVE LINE.

PEREIRA

1500 UTC UPDATE

ONLY SOME MINOR CHANGES MADE TO THE PREVIOUS EXCESSIVE RAINFALL
POTENTIAL OUTLOOK.  THE SLIGHT RISK AREA WAS EXTENDED SLIGHTLY
SOUTHWARD INTO NORTHWEST IA TO COVER THE LOWER FFG AREAS AHEAD OF
THE ONGOING CONVECTION MOVING NORTHWARD ACROSS THIS AREA.

ORAVEC


INITIAL DISCUSSION


...ERN PLAINS/MS VALLEY STATES...

MID-UPPER LEVEL TROUGH ENERGY/HEIGHT FALLS IN SEVERAL STREAMS WILL
BE EJECTING EAST NORTHEASTWARD OVER THE CENTRAL AND NRN PLAINS AND
INTO THE MID-UPPER MS VALLEY DAY1. INSTABILITY/THETAE ADVECTION
INCREASES WITH PW VALUES AHEAD OF THESE HEIGHT FALLS POOL UPWARDS
TO 2 STANDARD DEVIATIONS ABOVE THE MEAN ALONG/AROUND A DEVELOPING
SURFACE LOW AND ASSOCIATED FRONTAL SYSTEM. THIS COMBINED WITH WELL
DEFINED UPPER DIFFLUENCE AHEAD OF THE EJECTING HEIGHT FALLS WILL
SUPPORT POTENTIAL FOR CONVECTIVE FOCUS WITH WIDESPREAD MODERATE TO
HEAVY PRECIP TOTALS/MAXIMA SPREAD WITH FRONTAL SYSTEM PROGRESSION
DOWN TROUGH THE SRN PLAINS/MID-UPPER MS VALLEY...AS WELL IN ERNEST
BACK AROUND THE LOW WRAPPING FURTHER UP ACROSS THE UPPER MIDWEST
WITH MAX POTENTIAL PIVOT POINT CENTERED OVER MN. THERE REMAINS A
TYPICAL AMOUNT OF SPREAD WITH CONVECTIVE PRECIP DETAILS LEADING TO
AVERAGE (LOW) CONFIDENCE WITH THE DETAILS. HOWEVER...MODEL
CONSENSUS IS QUITE SUPPORTIVE OVERALL FOR WIDESPREAD MODERATE TO
HEAVY TOTALS STRETCHING ACROSS LARGE PORTIONS OF THE ERN PLAINS
AND ACROSS THE MID AND UPPER MS VALLEY WITH THE ARW AND TO A
LESSER EXTENT THE LIGHTER NBM PROBABLY MORE IN LINE WITH ONGOING
ACTIVITY AND WPC CONTINUITY.

ACCORDINGLY...ISSUED SLIGHT EXCESSIVE RAINFALL THREAT AREAS OVER
THE COMMA HEAD CENTERED OVER MN/NRN IA/WRN WI WITH CONSOLIDATED
ACTIVITY AND FROM E-CENTRAL OK/SE KS TO NW AR/SW-CENTRAL MO WHERE
THERE IS A THREAT FOR TRAILING/TRAINING HEAVY CONVECTION. THESE
BOTH ARE WITHIN A BROADER MARGINAL AREA.

...LOWER MS/CENTRAL COAST STATES...

PW VALUES REMAIN UPWARDS OF 2"+ FOR THE UPCOMING DAY 1 TIME PERIOD
AND THIS MAY SUPPORT ANOTHER ROUND OF WIDESPREAD SCATTERED SLOW
MOVING CONVECTION ACROSS THESE AREAS. LOW CONFIDENCE ON QPF
DETAILS...BUT AVAILABLE MOISTURE WOULD FUEL POTENTIAL FOR LOCALLY
HEAVY DOWNPOURS. THE LOWER MS VALLEY/CENTRAL GULF COAST MAY OFFER
THE MOST POTENTIAL WITHIN THIS BROAD AREA AS PER INCREASED GULF
INFLOW/INSTABILITY SO ISSUED A MARGINAL RISK AREA THERE.

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

SCHICHTEL
$$





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