Quantitative Precipitation Forecast
Issued by NWS

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000
FOUS30 KWBC 200027
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
827 PM EDT SAT AUG 19 2017

...VALID 01Z SUN AUG 20 2017 - 12Z SUN AUG 20 2017...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
45 ESE MTH 10 WSW MTH 35 WNW TMB 35 SW FPR FPR 15 NE PBI
35 E PMP.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
125 S GBN 60 ESE YUM 15 NNW GBN 20 SSW CGZ 20 N FHU 40 NNE DUG
65 NE SAD 45 SSW GNT 20 NE GNT 15 E SKX 40 N TCC 25 WSW CVS
20 E ATS 40 SSE GDP 50 W MRF 85 SW MRF.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 NNW BVN 20 N AUH OMA SDA 10 E BIE MHK 25 NE EWK 20 SE GBD
40 WSW HYS 45 SE GLD 30 NE GLD IML 20 S TIF 10 E VTN 35 NE ANW
20 NNW BVN.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
CGF 10 SW JHW 30 SSW ELM 30 W AVP 15 NNE UNV 10 ESE JST 2G4
20 W W22 15 NW PKB 45 SSE ILN 10 ENE LUK SGH CGF.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
85 SSE DUG 45 ENE DUG 20 NNW SVC 55 SSW ABQ 40 SE CQC 50 N ROW
ROW 25 W CNM 30 SSW GDP 85 WNW MRF 100 W MRF.


20/01Z UPDATE...

REMOVED MARGINAL RISK AREAS ACROSS THE OH VALLEY INTO PA WITH
CONTINUED PROGRESSION AND EXPECTED WEAKENING OF CONVECTIVE LINE
ACROSS THAT AREA OVERNIGHT.  ALSO REMOVED MARGINAL RISK ACRS THE
GULF COAST/SE STATES WHILE MAINTAINING MARGINAL RISK OVER EXTREME
SE FL GIVEN PROXIMITY OF ELY WAVE OVER THE WRN BAHAMAS WHICH COULD
SUPPORT SOME HEAVIER RAINS INTO SE FL OVERNIGHT AS AXIS OF GREATER
THAN 2.25 INCHES SHIFTS WWD ACRS SE FL WHICH WOULD LEAD TO SOME
VERY EFFICIENT RAINFALL MAKERS.  FINALLY...REDUCED SLIGHT/MARGINAL
RISK AREAS A TAD ACROSS THE SOUTHWEST WITH CONTINUED LOSS OF WIDER
SPREAD INSTABILITY TOWARD EVENING ACROSS THESE AREAS.  GREATER
RISK OF ORGANIZED ACTIVITY OVERNIGHT WILL REMAIN NEAR CONVECTIVELY
ENHANCED VORT THAT IS EXPECTED TO LIFT SLOWLY NWD INTO SRN/SW NM
OVERNIGHT.


...CENTRAL PLAINS...
SOME SLIGHT MODIFICATIONS WERE DONE TO THE PREVIOUS MARGINAL RISK
AREA WITH A SLIGHT EWD EXPANSION FROM NEBRASKA INTO WRN IA AS
EXPECTED OVERNIGHT CONVECTION AHEAD OF WEAK S/WV EMBDD IN WLYS
ACRS THE CNTL PLAINS IS EXPECTED TO STRENGTHEN ALONG THE LOW LEVEL
JET WHICH SHOULD SHIFT INTO WRN/CNTL IA BY MORNING.  PW VALUES ARE
FCST TO INCREASE TO NEAR 1.5" FROM SE NEB INTO SW/CNTL IA BY
MORNING UNDER 25 TO 30 KT SWLY FLOW.  WHILE OVERALL PATRN SUGGEST
RATHER MODEST FORWARD PROPAGATION OF EXPECTED CONVECTION ACRS NEB
INTO IA...A FEW HI RES MODEL RUNS SUGGEST POTNL FOR SPOTTY QUICK 1
TO 1.5 INCH RAINFALL AMOUNTS.   THOUGH THIS SHOULD NOT LEAD TO ANY
WIDESPREAD ORGANIZED FF THREAT...THESE AMOUNTS COULD PRODUCE SOME
ISOLD RUNOFF ISSUES IN TYPICAL AREAS OF SLOW/POOR DRAINAGE.


...SOUTHWEST STATES...

DEEP LAYERED MOISTURE SHOULD BEGIN MOVING NORTHWARD FROM OLD
MEXICO TONIGHT IN RESPONSE TO THE DEEPENING OF A TROUGH LOCATED
OFF CALIFORNIA.  THE MODELS DEPICT THE DEVELOPMENT OF A VORT MAX
SOUTH OF THE INTERNATIONAL BORDER WHICH EASES NORTHWARD...PERHAPS
THE RESULT OF CONVECTIVE FEEDBACK.  PRECIPITABLE WATER VALUES
INCREASE FROM AROUND 1.25 INCHES THIS MORNING TO OVER 1.5 INCHES
DURING THE OVERNIGHT HOURS ACROSS PARTS OF AZ.  WHILE THE PW
VALUES DO NOT CLIMB AS MUCH OVER AZ...THE MID AND UPPER LEVEL
DYNAMICS ARE STRONGER OVER NM.  WILL CONTINUE A SLIGHT RISK OVER
PORTIONS OF NM CLOSE TO THE DYNAMICS...AND EXTENDED THE MARGINAL
RISK BACK WESTWARD ALONG THE SOUTHERN AZ BORDER WHERE THE
PRECIPITABLE WATER PLUME IS BETTER DEFINED. THIS COULD BE THE
BEGINNING OF A MULTI DAY PERIOD OF POTNL FLASH FLOOD ISSUES.

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

SULLIVAN/MUSHER/BANN

$$




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