Quantitative Precipitation Forecast
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000
FOUS30 KWBC 190146
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
936 PM EDT MON AUG 18 2014

...VALID 03Z TUE AUG 19 2014 - 00Z WED AUG 20 2014...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
10 ENE EFT 10 SSE MRJ 10 SE DEH 20 S FKA 20 ESE AUM 10 WNW RST
20 NE RST 25 N LSE 20 SW ISW 10 SSW PCZ 20 ENE OSH 20 ESE SBM
30 ENE MKE 15 E RAC 10 NNW ENW 10 ENE EFT.

MODELS ARE IN FAIRLY GOOD AGREEMENT WITH THE EAST SOUTHEASTWARD
PUSH OF NORTHERN STREAM HEIGHT FALLS FROM THE UPPER MS VALLEY INTO
THE UPPER LAKES REGION INTO TUESDAY.  DIFFLUENT UPPER FLOW AHEAD
OF THESE HEIGHT FALLS IN AN AXIS OF ABOVE AVERAGE PW VALUES..1 TO
1.5+ STANDARD DEVIATIONS ABOVE THE MEAN..WILL SUPPORT WIDESPREAD
SCATTERED CONVECTION FROM THE UPPER MS VALLEY..INTO THE UPPER
LAKES AND EVENTUALLY SOUTHWARD ALONG THE TRAILING COLD FRONT INTO
THE MID MS VALLEY.  CONFIDENCE NOT GREAT WITH DETAILS..BUT
CONFIDENCE HIGHER THAT THERE WILL BE MODERATE TO LOCALLY HEAVY
RAINFALL TOTALS GIVEN THE ABOVE DYNAMICS/MOISTURE.  THE HI
RES---NSSL WRF AND NAM CONEST WERE USED PRIMARILY FOR QPF
DETAILS---WITH THEIR FAIRLY SIMILAR MAX AXES IN THE VICINITY OF
THE WARM FRONTAL BOUNDARY USED TO DEPICT THE GREATEST RISK OF
RUNOFF ISSUES.  ISOLATED RAINFALL TOTALS IN THIS AXIS OF 2-4"+
POSSIBLE.


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
10 SSW ATL 20 WNW CCO 25 ESE ANB 20 SW ANB 10 SE BHM 10 WSW BHM
10 WNW BHM 20 NNW BHM 15 SSE 3A1 10 ESE 3A1 15 NE 3A1 HSV
15 NNE DCU 20 NW MDQ 30 N MDQ 35 N MDQ 50 WNW CHA 25 NNE CHA
15 SSW RHP 10 N GVL LZU 10 SSW ATL.

KEPT THE SLIGHT RISK AREA OVER THE TN VALLEY..BUT REMOVED WESTERN
PORTIONS OF THE PREVIOUS AREA WHERE THIS NEXT MCV HAD MOVED THRU.
VERY HIGH MOISTURE IS ALSO IN PLACE THIS REGION..AS PER OBSERVED
PWS THIS EVENING APPROACHING 2 INCHES AT BNA..BUT LIKE THE SYSTEM
OFF TO ITS NORTH AND EAST..THIS ONE IS ALSO PROGRESSIVE.  THERE
COULD BE A BRIEF PERIOD OF CELL TRAINING AND/OR BACK BUILDING IN
THE LOW LEVEL WESTERLY FLOW REGIME..WHICH WOULD ENHANCE RAINFALL
AMOUNTS..BUT THIS SHOULD BE OF A VERY ISOLATED NATURE.  ISOLATED
1-2 INCH RAINS IN AN HOUR OR TWO POSSIBLE..WITH THIS THREAT
PROBABLY DECREASING LATER TONIGHT.


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
40 E 40G 25 WNW SOW 25 NE SAD 45 NE DUG 35 ESE DUG 65 SSE DUG
85 S DUG 75 NNE MMHO 80 N MMHO 75 SW OLS 100 W OLS 90 SSW GBN
75 SE YUM 55 S NYL 50 SSW NYL 50 S IPL 40 S NJK 20 WSW NJK
20 NE TRM 45 NW BLH 45 WNW EED 30 SW HND 20 W VGT 40 NE DRA
95 S ELY 50 WNW MLF 15 NNE U24 30 WNW PUC 15 SW PUC 40 W 4HV
25 NE GCN 40 E 40G.

ABOVE AVERAGE PW VALUES--- 1 TO 2 STANDARD DEVIATIONS ABOVE THE
MEAN---WILL CONTINUE TO BE FUNNELED NORTH AND NORTHEASTWARD THIS
PERIOD ACROSS THE SOUTHWEST INTO THE GREAT BASIN BETWEEN THE
CLOSED LOW DIVING SOUTHWARD INTO NORTHERN TO CENTRAL CALIFORNIA
AND THE UPPER HIGH OVER THE SOUTHERN ROCKIES.  VERY DIFFLUENT
UPPER FLOW EXPECTED AHEAD OF THIS CLOSED LOW AND WELL DEFINED
VORTS MOVING NORTH NORTHEASTWARD IN THE HIGH PW AXIS.  THIS WILL
SUPPORT WIDESPREAD CONVECTIVE ACTIVITY THIS PERIOD FROM THE
SOUTHWEST INTO THE GREAT BASIN---WITH MODEL CONSENSUS FOR
POTENTIAL OF WIDESPREAD MODERATE TO HEAVY PRECIPITATION
TOTALS---ALONG WITH POTENTIAL FOR FLASH FLOODING.  THE HI RES ARW
AND IN HOUSE PSEUDO BIAS CORRECTED ENSEMBLE MEAN USED FOR QPF
DETAILS THIS PERIOD.


...SOUTHEASTERN VA...

REMOVED THE SLIGHT RISK..BUT SOME LOCALLY HEAVY RAINS ARE STILL
POSSIBLE UNTIL 06Z OR SO.  THE STILL WELL DEFINED MCV/VORT MAX
WILL MOVE THRU THIS REGION BY 06Z OR SHORTLY THEREAFTER..AND COULD
PRODUCE SOME ENHANCED CONVECTION IN AN AIRMASS THAT IS QUITE
MOIST..WITH OBSERVED PWS THIS EVENING OVER 2 INCHES. THE SYSTEM IS
HOWEVER QUITE PROGRESSIVE..SO ANY HEAVIER RAINS SHOULD BE
SHORT-LIVED..LESSENING THE FLOODING THREAT.  SOME VERY ISOLATED
1-2 INCH RAINS IN A COUPLE OF HOURS WILL BE POSSIBLE.


...CENTRAL/WESTERN TX...

ANALYSIS OF THE 00Z RAOBS DID SHOW THE SMALL MID LEVEL CIRCULATION
JUST NORTH OF THE BIG BEND..WITH THIS SYSTEM NOT FORECAST TO MOVE
VERY MUCH THE REMAINDER OF TONIGHT INTO TUESDAY.  SOME VERY HEAVY
RAINFALL AMOUNTS HAVE FALLEN IN THE VICINITY OF THIS VORT..WITH
THE POTENTIAL FOR SOME ADDITIONAL ISOLATED HEAVY AMOUNTS THRU
MONDAY NIGHT IN A VERY HIGH MOISTURE AIRMASS..WITH PWS ABOVE 1.75
INCHES IN PLACE.

TERRY
$$




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