Quantitative Precipitation Forecast
Issued by NWS

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000
FOUS30 KWBC 200829
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
428 AM EDT SAT AUG 20 2016

...VALID 12Z SAT AUG 20 2016 - 12Z SUN AUG 21 2016...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
45 S CYLD 45 NE ANJ 10 NE ANJ 20 E ISQ 20 NNW MNM 25 NNW MNM
30 NW MNM 15 E RHI 15 ESE PBH 10 ENE RCX 15 WNW RCX 15 N RPD
15 ENE RZN 20 ESE CDD 15 ENE CDD 10 SW SUW SUW 25 ENE BFW CWEC
15 NE CWEC 25 ENE CXCA 10 SSE CYGQ 60 ESE CYGQ.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
90 SW 6R6 40 ENE 6R6 30 NNE SJT 30 S DYS DYS 40 N DYS
60 SSW F05 35 SW SPS 25 SSE SPS 10 SW GYI 30 N PRX 25 E FLP
20 SSW CGI 20 NNE HOP 15 WSW BWG 15 ESE BWG 20 E GLW 20 WNW SME
20 S LEX 25 NNE LEX 10 WNW HAO 20 W DAY 15 SSE AOH 10 NNW 4I3
20 E 4I3 15 SSW PHD PIT 15 E AGC 2G4 30 SSE EKN 15 WSW PSK
15 W TNB 30 SSW RHP 20 SSW GAD 45 SW GWO 30 E BAD 20 S 11R
30 W ALI 25 S MMIO.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
80 SW DRT 50 WSW DRT 20 SSE E29 25 WNW JCT 35 NW 6R9 25 SSW GDJ
20 ENE AUS 25 SE RND 25 NNE LRD 45 W MMNL 45 ENE MMMV.


UPPER LAKES

THE STRONG VORT ROTATING THRU THE AMPLIFYING UPPER TROF OVER THE
UPPER MS VALLEY/UPPER LAKES REGION WILL SUPPORT AN ENHANCING COMMA
HEAD/DEFORMATION PRECIPITATION AREA FROM PORTIONS OF THE UPPER MS
VALLEY---NORTHEASTWARD INTO THE UPPER LAKES.  WITH FAIRLY GOOD
MASS FIELD EVOLUTION AMONG THE LATEST MODELS---THERE IS SIMILAR
QPF DISTRIBUTIONS.  HEAVY RAINS LIKELY IN THIS COMMA HEAD
REGION---WITH AREAL AVERAGE 1-2"+ TOTALS FROM NORTHERN WI INTO
LARGE PORTIONS OF THE U.P. OF MI--- WITH ISOLATED TOTALS GREATER
THAN 3" POSSIBLE---ESPECIALLY OVER THE WESTERN TO CENTRAL U.P. AND
FAR NORTHERN WI WHERE LAKE ENHANCEMENT TO THE PRECIPITATION
POSSIBLE FROM STRONG NORTHERLY TO NORTHWESTERLY FLOW OFF OF LAKE
SUPERIOR.  A MARGINAL RISK OF EXCESSIVE RAINFALL AMOUNTS DEPICTED
ACROSS THESE AREAS.

CENTRAL APPALACHIANS/UPPER OH VALLEY---TN VALLEY

THE FRONTAL BOUNDARY FROM THE AMPLIFYING TROF OVER THE UPPER MS
VALLEY/UPPER LAKES IS EXPECTED TO BE VERY PROGRESSIVE TO THE EAST
AND SOUTHEAST THROUGH THE LOWER LAKES---OH VALLEY AND TN VALLEY.
WHILE PW VALUES WILL BE ABOVE AVERAGE IN A NARROW BAND ALONG AND
AHEAD OF THE FRONT---2 TO 2.5 STANDARD DEVIATIONS ABOVE THE
MEAN---THE PROGRESSIVE NATURE OF THE BOUNDARY WILL LIMIT POTENTIAL
FOR VERY HEAVY TOTALS.  STILL---WELL DEFINED FRONTAL CONVERGENCE
IN THIS HI PW AXIS WILL SUPPORT LOCALLY HEAVY PRECIP TOTALS ALONG
AND AHEAD OF THIS FRONT.  A MARGINAL RISK AREA WAS DEPICTED FROM
THE CENTRAL APPALACHIANS/UPPER OH VALLEY REGION INTO THE TN VALLEY
WHERE THERE ARE POCKETS OF RELATIVELY LOWER FFG VALUES IN 1-1.5"
RANGE IN AN HOUR.

SOUTHERN PLAINS INTO THE LOWER MS VALLEY

THE WESTERN PORTION OF THE FRONT ASSOCIATED WITH THE AMPLIFYING
MID U.S. TROF CURRENTLY PRESSING SOUTHWARD INTO THE SOUTHERN
PLAINS IS EXPECTED TO SLOW SATURDAY AS IT PRESSES FARTHER SOUTH
INTO THE SOUTHERN PLAINS AND LOWER MS VALLEY.  THIS WILL ALLOW THE
AXIS OF ABOVE AVERAGE PW VALUES TO PERSIST LONGER IN THE VICINITY
OF THE FRONT ACROSS THE SOUTHERN PLAINS INTO THE LOWER MS
VALLEY--SUPPORTING POTENTIAL FOR LOCALLY  HEAVY PRECIP TOTALS
ACROSS NORTHEAST TX INTO THE LOWER MS VALLEY.  ISOLATED RUNOFF
ISSUES POSSIBLE---ESPECIALLY ACROSS NORTH CENTRAL TX EARLY IN
PERIOD WHERE SOUTHEASTWARD MOVING CONVECTION MAY MOVE ACROSS AREAS
OF LOWERED FFG VALUES.

SOUTH CENTRAL TO NORTHEAST TX

TO THE SOUTH OF THE FRONT MOVING INTO THE SOUTHERN PLAINS---THERE
IS A STRONG MODEL SIGNAL FOR HEAVIER RAINFALL AMOUNTS IN THE
VICINITY OF 100W FROM THE U.S./MEXICAN BORDER---NORTHEASTWARD
ACROSS SOUTH CENTRAL TX IN THE VICINITY OF SAN
ANTONIO..AUSTIN---WACO.  THIS IS IN ASSOCIATION WITH VORTS
EXPECTED TO LIFT NORTHEASTWARD FROM NORTHEAST MEXICO INTO CENTRAL
TO NORTHEAST TX.  THERE ARE A VARIETY OF MODEL SOLUTIONS WITH
RESPECT TO THE DETAILS OF THESE VORTS---BUT GENERAL AGREEMENT ON
POTENTIAL FOR HEAVY TO ISOLATED EXCESSIVE RAINFALL AMOUNTS IN THIS
AXIS.   GIVEN THE BETTER OVERALL AGREEMENT ON HEAVY RAIN
PLACEMENT---A SLIGHT RISK AREA WAS DRAWN ACROSS THESE AREAS.

ORAVEC
$$





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