Quantitative Precipitation Forecast
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FOUS30 KWBC 172354
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
753 PM EDT SAT JUN 17 2017

...VALID 2353Z SAT JUN 17 2017 - 12Z SUN JUN 18 2017...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 WNW MTV 10 NE UKF MRN 20 NW FQD 15 NW AVL 35 NNW AVL
10 NNE VJI BKW 15 WNW 2G4 15 SE LBE 10 NNE JST AOO 25 WNW HGR
OKV 10 NW KW66 10 ESE CHO 30 SSW SHD 20 NE MTV 20 N GSO
20 WNW MTV.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
15 NNE FSM 15 E CQB 15 W END 25 SW PTT 30 ESE RSL 15 NE CDJ SFY
10 NNE MKE P58 25 N CTZR 10 SE RMY 15 SSE LAF 15 SE CUL
20 SSW CIR 20 SSE UNO 15 NNE FSM.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
30 SE CDJ 10 E EOK DKB 10 ENE MDW DNV 25 SSW SAR VBT 25 WNW PNC
10 NNW EWK 30 SE CDJ.


2330 UTC UPDATE

CHANGES TO PREVIOUS DAY 1 EXCESSIVE RAINFALL OUTLOOK INCLUDED AN
EXPANSION OF THE MARGINAL AND ESPECIALLY THE SLIGHT RISK AREAS
ACROSS EASTERN KS-NORTHEAST OK THROUGH MUCH OF MS AND IL.
MESOANALYSIS TRENDS CONTINUE TO SHOW SIGNIFICANT DEEP LAYER
INSTABILITY POOLED INTO CENTRAL-EASTERN PORTIONS OF KS-OK
(MIXED-LAYER CAPES OF 4000-6000+ J/KG WITH SOME CIN
PERSISTING...AS PER THE 21Z KTOP RAOB WITH A DEFINITIVE CAP NOTED
BETWEEN 850-800 MB). THE UPPER SHORTWAVE TRAVERSING SD PER THE
LATEST SATELLITE WV IMAGERY WILL CONTINUE ON A SOUTHEASTERLY
TRAJECTORY INTO NORTHERN IA BY 0600 UTC. INCREASING BROAD-SCALE
UPPER DIVERGENCE/DEEP LAYER ASCENT AHEAD OF THIS WAVE...CONCURRENT
WITH AN UPTICK IN LOW LEVEL FRONTOGENESIS...WILL SPUR MULTIPLE
CLUSTERS OF ORGANIZED CONVECTION THAT WILL GROW UPSCALE THIS
EVENING...ONE ACROSS CENTRAL-EASTERN KS WITH THE OTHER ACROSS
CENTRAL-EASTERN MO INTO WESTERN IL PER THE LATEST HIGH-RES CAM
GUIDANCE TRENDS. WHILE THE VARIOUS CAMS ARE NOT VERY WELL
CLUSTERED WITH THE EVOLUTION OF THE MCS/S OVERNIGHT...THERE DOES
SEEM TO BE A MULTI-MODEL SIGNAL MULTIPLE PCPN MAXIMA THROUGH 1200
UTC...ONE ACROSS EASTERN KS-NORTHEAST OK AND THE OTHER OVER
CENTRAL-EASTERN MO AND WEST-CENTRAL IL...BOTH AHEAD OF THE SURFACE
BOUNDARY AND BENEFITING FROM THE AFOREMENTIONED STRONG DEEP-LAYER
INSTABILITY...INCREASING DYNAMICAL FORCING (WEAKENING CAP)...AND A
STRENGTHENING LLJ WITH TIME OVERNIGHT. AS THE LOW-LEVEL INFLOW
INCREASES TO 40-50 KTS AND VEERS MORE WESTERLY WITH TIME OVERNIGHT
(FROM SW TO WSW)...CELL TRAINING WILL BECOME MORE LIKELY AFTER 03Z
AS THE LOW-LEVEL INFLOW BECOMES MORE PARALLEL TO (WHILE EXCEEDING
THE MAGNITUDE OF) THE MEAN 850-300 MB FLOW. FORECAST CORFIDI
VECTORS RESPOND BY VEERING FROM NORTHERLY TO EASTERLY WHILE
DECREASING TO 10 KTS OR LESS. DUE IN LARGE PART BECAUSE OF
THIS...SOME OF THE MESOSCALE GUIDANCE (NSSL-WRF AND NAM CONUS NEST
IN PARTICULAR) SHOW POCKETS OF 3-6" OF RAIN WITHIN THE SLIGHT RISK
AREA...ESPECIALLY ACROSS CENTRAL-EASTERN MO INTO WEST-CENTRAL IL.

HURLEY




INITIAL DISCUSSION

NORTHERN PLAINS/GT LAKES SOUTHWARD INTO THE CNTL PLAINS/MID MS
VALLEY...

A NORTHERN STREAM S/WV WILL DIG SOUTHEASTWARD FROM THE NRN
INTERMOUNTAIN REGION EARLY SATURDAY WITH ASSOCD HEIGHT FALLS
SUPPORTING LOW PRESSURE DEVELOPMENT ALONG AN INTENSIFYING COLD
FRONT OVER THE MO VALLEY THAT WILL LIFTING NEWD SAT NIGHT TOWARD
THE GT LAKES. THE COMBINATION OF STG HEIGHT FALLS AND..POOLING OF
2 INCH PWS ALONG THE FRONT AND STEEPENING LAPSE RATES SHOULD
SUPPORT RAPID INTENSIFICATION OF THUNDERSTORMS MOST NOTABLY ACROSS
ERN IA/NRN MO AND THE NRN PORTION OF IL BY LATE SAT.  THESE STORMS
SHOULD CONTINUE TO EXPAND IN COVERAGE WITH FAVORABLE SHEAR AND
MOISTURE PROFILES LIKELY SUPPORTING ORGANIZED SQLN DEVELOPMENT
THAT WILL EXPAND SOUTH AND EAST OVERNIGHT.  THE NAM WAS A BIT MORE
DVLPD BOTH WITH THE S/WV TROF AND ASSOCD SFC LOW WHICH RESULTED IN
IT PLACING ITS HEAVIER EMPHASIS FARTHER NORTH.  THE CONSENSUS OF
THE WRF ARW..NMM..AND CANADIAN GEM INDICATED A POTNL E/W FOCUS OF
HEAVIER RAINS SOUTH OF THE NAM AND MORE ACROSS CNTL IL INTO SE
IA/NE MO WHERE E/W ALIGNMENT OF THE FRONT EAST OF THE LOW WILL BE
CONDUCIVE FOR TRAINING AND PSBL ELEVATED RISK OF EXCESSIVE RAINS
EARLY SAT NIGHT AND HAVE INTRODUCED A SLIGHT RISK ACROSS THIS
REGION.  POTNL WILL EXIST HERE FOR ISOLD 3 TO 5 INCH IN RAINS IN A
COUPLE HOURS.   ACCELERATION OF POTNL SQLN TO THE SOUTH ACRS KS/MO
INTO OK/AR IS EXPECTED SAT NIGHT TOWARD MORE FAVORABLE
INSTABILITIES WITH AMPLIFYING NWLY FLOW AND WILL LIKELY SEE SOME
INTENSE BUT SHORTER LIVED RAIN RATES GIVEN THE FAVORABLE
MSTR/INSTABILITY PROFILES. STILL COULD NOT RULE OUT ISOLD RUNOFF
ISSUES WHERE BOWING PORTION OF LINE MAY BRIEFLY SLOW OR HANG UP.
FARTHER NORTH...STEEPENING LAPSE RATES AHEAD OF MAIN CORE OF
HEIGHT FALLS ACRS THE NRN PLAINS INTO THE WRN GT LAKES WILL
SUPPORT MDT CONVECTIVE RAIN AMOUNTS THERE..WHILE AN UPTICK IN
CONVECTION IS ALSO EXPECTED AHEAD OF THE DEEPENING SFC WAVE SAT
AFTN/NIGHT FROM PORTIONS OF ERN WI EWD INTO LOWER MI.  HI RES
GUIDANCE SUGGEST SOME SOME HEAVIER RAIN AMOUNTS OF BETWEEN 1 TO 2
INCHES OVER PORTIONS OF LOWER MI WITH MEAN LAYER FLOW PARALLELING
THE SFC FRONT SUPPORTING POTNL TRAINING.  THESE AMOUNTS COULD
APPROACH SOME OF THE LOWER FFG VALUES ESPECIALLY OVER ERN PORTIONS
OF THE LOWER PENINSULA.

CNTL GULF COAST/FL PANHANDLE...

A FAIRLY ORGANIZED CONVECTIVELY INDUCED MID LEVEL LOW IS FCST TO
SLOW AND MEANDER NEAR THE GULF COAST IN VCNTY OF THE AL/FL REGION
THIS PD AS IT MOVES INTO A REGION OF RELATIVELY WEAK STEERING
FLOW.   THERE WILL REMAIN THE POTNL FOR LOCALIZED HEAVIER RAINS
NEAR THE UPPER LOW THROUGH THE PD AS MOIST SWLY LOW LEVEL FLOW
MAINTAINS MDTLY HIGH PWS ACRS THE REGION WITH WEAK CYCLONIC FLOW
ALOFT.  ISOLD RUNOFF ISSUES WILL BE PSBL FROM SE MS THROUGH SRN AL
AND PORTIONS OF THE FL PANHANDLE ESPECIALLY IN AREAS WHERE
ANTECEDENT CONDS INDICATE MOIST SOIL CONDS FROM RECENT RAINS.

SULLIVAN

$$





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