Quantitative Precipitation Forecast
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FOUS30 KWBC 191438
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1037 AM EDT FRI MAY 19 2017

...VALID 15Z FRI MAY 19 2017 - 12Z SAT MAY 20 2017...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 S HSP BCB 20 SW MKJ 25 S 1A6 CSV 30 WSW BNA 10 NW MKL
15 NE BVX RUE 30 SW MWT 15 W OSA 20 ESE LNC 15 ESE ACT 10 E GTU
30 W ERV 50 NNW DRT 45 NW E29 20 ENE SWW 30 SW F05 10 NNW LTS
30 SW JWG 10 NNW AVK 20 NNE CNK 10 SE OLU 25 S YKN 25 WNW LRJ
10 SSE SPW 20 SSE MCW 20 ESE OLZ RPJ OKK OSU 15 SW PHD AFJ
15 NW 2G4 10 W CBE 15 E W99 25 NNW SHD 25 NE HSP 15 S HSP.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
35 N PRX 20 E INJ 10 WSW GRK 15 S 6R9 15 NNW T82 20 E JCT
15 NE JCT 50 SW BWD 30 NNW BWD 35 SW RPH 25 NW RPH 30 WSW SPS
10 ESE F05 10 NNW FDR END 35 WSW FNB 15 S CSQ 25 SW OTM
10 NNW FSW 30 ESE MQB 15 SSE AAA 10 SW 1H2 10 W ENL 15 SSE SUS
20 NW VIH 25 NNE SGF 15 NNW FSM 35 N PRX.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 ESE BKW 10 NNE 6V3 20 NNE 1A6 15 S EKQ 35 SSE GLW 20 S BWG
15 NW BWG 25 S FTK LEX 15 WSW CRW 30 NW LWB 20 ESE BKW.

MODERATE RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 NNE RPH 10 NNW SPS 20 SSW LAW 20 S CHK 15 NW SWO 20 E WLD
20 NNE EMP 15 N TOP 25 SW STJ STJ 10 WNW CDJ 30 ESE CDJ
35 NNE DMO DMO 10 S DMO 40 NNW SGF 20 W SLG AQR 15 WNW NFW
15 W MWL 25 NNE RPH.


15Z UPDATE...

THE ONLY CHANGE TO THE PREVIOUS EXCESSIVE RAINFALL OUTLOOK AREA AT
THIS POINT WAS TO INTRODUCE A SLIGHT RISK AREA ACROSS PARTS OF FAR
NORTHERN TN...CENTRAL/EASTERN KY AND INTO SOUTHERN WV WHERE
MORNING CONVECTION HAS DEVELOPED AND EXPANDED IN COVERAGE OVER THE
LAST FEW HOURS WHILE ALSO TENDING TO TRAIN OVER THE SAME AREA.
MORNING SURFACE OBSERVATIONS COUPLED WITH THE LAST COUPLE OF RAP
ANALYSES SHOW THERE IS A RATHER NOTABLE POOL OF MOISTURE AND AT
LEAST SOME MODEST INSTABILITY POOLED UP ACROSS CENTRAL/NORTHERN TN
AND SOUTHERN KY...WITH THE 12Z KBNA RAOB DEPICTING A 1.64 INCH
PWAT...AN LI OF -6 AND A K-INDEX OF 40. ALL OF THIS ENERGY IS
LIFTING NORTHEAST WITHIN A BROADLY CONFLUENT LOW LEVEL FLOW
PATTERN...AND COINCIDING WITH SOME 250 MB UPPER JET DIVERGENCE.
THEREFORE...WILL BE EXPECTING SOME MAINTENANCE OF THIS AXIS OF
CONVECTION OVER THE NEXT SEVERAL HOURS WITH A NOTABLE FLASH FLOOD
THREAT. PLEASE CONSULT MPD #294 FOR MORE DETAILS ON THIS.

ORRISON

PREVIOUS DISCUSSION...

...SOUTHERN TO CENTRAL PLAINS---LOWER MO VALLEY INTO THE MID MS
VALLEY...

A FAIRLY BROAD SLIGHT AND MODERATE RISK AREAS WERE MAINTAINED FROM
PREVIOUS WPC OUTLOOKS---STRETCHING ACROSS LARGE PORTIONS OF THE
SOUTHERN TO CENTRAL PLAINS INTO THE LOWER MO VALLEY AND MID MS
VALLEY.  A SURFACE COLD FRONT IS EXPECTED TO PRESS EAST
SOUTHEASTWARD THROUGH THE SOUTHERN  PLAINS--WHILE REMAINING NEARLY
STATIONARY FROM THE LOWER MO VALLEY INTO THE MID MS VALLEY REGION.
 ANOTHER ROUND OF ACTIVE CONVECTION LIKELY LATER FRIDAY AFTERNOON
CONTINUING INTO THE OVERNIGHT HOURS OF EARLY SATURDAY IN THE
VICINITY OF THESE FRONTS AS THE STRONG CENTRAL ROCKIES CLOSED LOW
PUSHES EASTWARD INTO THE CENTRAL PLAINS THIS PERIOD.  GIVEN THE
VERY FAVORABLE PATTERN FOR WIDESPREAD HEAVY RAINS AHEAD OF THIS
CLOSED LOW---STRONG UPPER DIFFLUENCE---STRONG FRONTAL CONVERGENCE
IN AN AXIS OF PW VALUES 1 TO 2 STANDARD DEVIATIONS ABOVE THE
MEAN---CONFIDENCE IS FAIRLY HIGH FOR ADDITIONAL WIDESPREAD HEAVY
PRECIP AMOUNTS STRETCHING ACROSS THESE AREAS.  THE USUAL CAVEAT OF
LOWER SHORTER TERM CONFIDENCE GIVEN THE INHERENT DIFFICULTIES WITH
THE FORECASTING OF MESOSCALE DETAILS AND RECENT MODEL VERIFICATION
WHICH SHOWED A WIDE RANGE OF SKILL AMONG THE MODELS BUT NO
CONSISTENT SUPERIOR PERFORMING MODEL.  AFTER POST 1200 UTC FRIDAY
WEAKENING TO THE CURRENT ORGANIZED ACTIVITY---CONVECTION SHOULD
AGAIN BECOME MORE ORGANIZED LATE AFTERNOON INTO THE OVERNIGHT
HOURS OF FRIDAY/EARLY SATURDAY AS THE LOW LEVEL INFLOW INTO THE
FRONT STRENGTHENS.  THE ONGOING HEAVY RAINS WILL LIKELY LOWER FFG
VALUES ACROSS THESE AREAS---WITH THE ADDITIONAL HEAVY RAIN
POTENTIAL LATER FRIDAY INTO EARLY SATURDAY SUPPORTING INCREASED
RISK OF RUNOFF ISSUES ACROSS THESE AREAS.  CHANGES TO THE PREVIOUS
OUTLOOK WERE TO NARROW THE SLIGHT RISK AREA FROM THE LOWER MO AND
MID MS VALLEY REGIONS AND EXTEND THE MODERATE RISK SOUTHWARD INTO
FAR NORTH CENTRAL TX.

ORAVEC
$$




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