Quantitative Precipitation Forecast
Issued by NWS

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FOUS30 KWBC 202352
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
752 PM EDT SUN AUG 20 2017

...VALID 01Z MON AUG 21 2017 - 12Z MON AUG 21 2017...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
40 N MMH 30 SSE BIH 30 NW IYK 30 SE PTV 30 NE VIS 45 ENE MCE
45 ESE MHR 10 W BLU 15 E TVL 40 N MMH.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
60 NNE MMHO 25 S OLS 45 ENE DMA 40 W SOW 25 NE SJN 35 SSE FMN
30 SW TEX 30 SW GUC 35 SSE MYP 30 E CCU 10 SW MNH 25 S PUB
35 NW CAO 25 NNW CAO 15 NNW DUX AMA 50 S LBB 20 S FST 115 S MRF
125 ESE MMCU.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
30 N IMT 25 NNE ISQ 20 NW PLN 20 NNE FKS 15 SSE PCZ 10 E OVS
10 SSE JVL GYY 10 SSE SBN 25 NNE LAF 20 NNW BMI 20 ESE EOK
40 NNW COU 15 E STJ 10 S FET 25 SE ONL 25 NE ONL 20 N OTG
10 SE LVN 20 N ONA 10 ENE AUW 30 N IMT.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
50 WNW MMH 55 S TVL 20 S TVL 30 SSE TVL 40 NW MMH 25 WNW MMH
20 SSW MMH 40 WSW MMH 50 WNW MMH.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
110 SW MMCS 40 WSW MMCS ALM 15 W 4CR 10 SSW 4MY 25 WSW LVS
20 E LVS 30 NNE TCC 40 NE TCC 35 W AMA 40 W LBB 20 NE INK
25 S MRF 70 E MMCU 60 ESE MMCU.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 E TQE 15 S SUX LRJ 20 WNW FOD 30 NNW MIW 20 NNW MXO
10 NNE AWG 15 NW OXV 10 ENE AIO 15 E TQE.


21/01Z UPDATE..

LOWER MO VALLEY INTO THE MID AND UPPER MS VALLEY AND UPPER GREAT
LAKES

BEHIND MORNING/AFTN MCS ACRS THE MIDWEST AND SUBSEQUENT INCREASE
IN CONVECTIVE INHIBITION...MODELS HAVE STRUGGLED WITH AXIS OF
STRONGER REDEVELOPMENT FOR THE REMAINDER OF THE OVERNIGHT ACROSS
THE MIDWEST/MO VALLEY..THOUGH HI RES GUIDANCE HAS GENLY BEEN
SIGNALING A HEAVIER RAIN FOCUS ACROSS PORTIONS OF CNTL AND NRN IA.
 THIS AS HIGHER MLCAPES ACRS SRN/ERN NEB ARE DIRECTED NEWD
OVERNIGHT WITH VEERING LOW LEVEL JET AHEAD OF FRONTAL BNDRY
DROPPING VERY SLOWLY SWD ACRS SRN MN. 18Z HRRR EXP GENLY ALIGNS
WELL WITH THE WRF ARW AND NSSL WRF WITH HEAVIER RAIN WITH POTNL
TRAINING ACRS CNTL IA WHILE THE 21Z HRRR HAS ITS AXIS ABOUT 50- 75
MILES FARTHER SOUTH..AND EXTENDS A BIT WWD INTO ERN NEB..WHILE
ALSO INDICATING SPOTTY HEAVIER RAINS FARTHER N ACROSS SRN MN..MORE
ALONG THE FRONT.  WITH THE CONSENSUS OF A MORE NRN FOCUS
OVERNIGHT...HAVE NARROWED THE SLIGHT RISK AREA WHILE SHIFTING MORE
TOWARD CNTL PORTIONS OF IA..GIVEN A SLIGHTLY BROADER CONSENSUS OF
THE HRRR EXP...NSSL WRF..AND WRF ARW.  THESE MODEL SUGGEST
POTENTIAL FOR SHORT TERM RAINS OF 1.5"+ WHICH COULD RESULT IN
LOCAL RUNOFF ISSUES.


SIERRA NEVADA / AZ-NM INTO SOUTHERN CO

ACROSS THIS REGION...AN EWD SHIFT TO THE SLIGHT RISK AREA WAS MADE
TO COINCIDE WITH THE MORE FAVORABLE INSTABILITY WHICH HAS SET UP
EAST OF THE DENSER OVERCAST ASSOCD WITH VORT/MCV LIFTING NEWD ACRS
PARTS OF CNTL/WRN NM THIS EVENING.  THE EWD SHIFT ALIGNS WELL WITH
CURRENT RADAR/SATL TRENDS AS WELL AS RECENT HRRR RUNS WHICH SHOW
NUMEROUS SHWRS/TSTMS OCCURRING FROM WRN TX THROUGH MUCH OF SE/ERN
NM AS OF 23Z.  SOME NRN AND WRN PROPAGATION OF CELLS WILL ALLOW
FOR CELL MERGERS WITH ACTIVITY FORMING AND MOVING EWD OFF
SACRAMENTO/GUADALUPE/AND SANGRE DE CHRISTO MTNS THIS
EVENING/OVERNIGHT WHILE OTHER STORMS DVLP AND MOVE NWD ACRS WRN TX
AND FROM THE MTNS OF NRN MEX IN PSBL REPEAT ACTION ACRS WRN TX.
AS A RESULT..LOCAL FLASH FLOOD ISSUES WILL BE PSBL ACRS THESE
AREAS FOR AT LEAST THE EARLY OVERNIGHT PD.  SEE MPD# 0708 VALID
UNTIL 0520Z FOR ADDITIONAL INFORMATION.

ACROSS THE SIERRA NEVADA...MODEST DEEP-LAYER INSTABILITY (MUCAPES
1000-1500 J/KG) ALONG WITH ANOMALOUS MOISTURE (PWAT VALUES ~2
STANDARD DEVIATIONS ABOVE NORMAL)...DIFLUENT UPPER FLOW/PERIODIC
DPVA...AND OROGRAPHIC ENHANCEMENT WILL FAVOR MORE WIDESPREAD
DIURNAL CONVECTION ALONG THE SIERRA...PARTICULARLY THE WESTERN
SLOPES. PER THE HIGH-RES GUIDANCE...LOCAL AMOUNTS BETWEEN 1-2+
INCHES ARE ANTICIPATED.

SULLIVAN/MUSHER/HURLEY

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