Quantitative Precipitation Forecast
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FOUS30 KWBC 261958
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
358 PM EDT FRI JUN 26 2015

...VALID 1958Z FRI JUN 26 2015 - 12Z SAT JUN 27 2015...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
TDZ 15 WSW HZY DUJ 25 S UNV 10 N MRB OKV 25 W CJR 15 E PTB
20 SSE EDE NKT 15 S NCA 15 S DPL 15 ESE RDU 20 S ROA 40 N LNP
20 SW JKL EKQ 35 SW BNA 10 SSE OLV 10 SSW JBR 15 N CGI 20 SE MVN
10 W 1H2 25 WSW TAZ 20 ESE PPQ 15 SSW UIN 15 WSW MQB 20 ESE PNT
TDZ.

MODERATE RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
10 NNE HUF 20 S CMI 10 NW CMI 20 WNW LAF 20 ENE OKK 15 ENE FDY
25 NNE MFD 10 WSW CAK 25 WSW HLG 15 S PKB 30 WSW HTS 35 SW LEX
15 N BWG 20 E OWB 30 ESE HNB 20 WSW CVG 20 WNW CVG 15 SW IND
10 NNE HUF.


DAY 1

21Z UPDATE...
MADE SHIFT NWD WITH MDT RISK AREA ACRS THE OH VALLEY AS LONGER
DURATION SYNOPTICALLY DRIVEN WARM FRONTAL RAINS CONTINUE TO FOCUS
A BUIT FARTHER NORTH WITH 12Z MODEL RUNS ACRS THE OH VALLEY.  A
RATHER BROAD MDT RISK WAS INDICATED WITH POTNL FOR CONVECTIVE LINE
SEGMENTS FARTHER SOUTH IN WARM SECTOR FEEDING OFF OF RATHER HIGH
PWS ..MODEST MSTR TRANSPORT..AND HI SBCAPES THAT COULD BRIEFLY
TRAIN PRODUCING SOME ISOLD SHORT TERM RAINFALL AMOUNTS OF 2 TO 3
INCHES.  SULLIVAN   PREVIOUS DISCUSSION FOLLOWS.

...MID MISSISSIPPI VALLY EAST THROUGH THE OHIO VALLEY AND INTO THE
CENTRAL/NORTHERN APPALACHIANS...

A MODERATE RISK OF EXCESSIVE RAINFALL IS FORECAST WHERE DEEP
SYNOPTIC SCALE ASCENT OVERLAPS WITH THE NORTHERN REACHES OF AN
INSTABILITY AXIS...ORIENTED WEST TO EAST. VERY LOW FLASH FLOOD
GUIDANCE VALUES OWING TO RECENT WET WEATHER...WAS ALSO A FACTOR IN
OUTLINING THE MODERATE RISK AREA...WHICH STRETCHES ACROSS CENTRAL
IL TO SOUTHERN IN AND SW OH...CATCHING JUST A SMALL PART OF KY.

STEEP HEIGHT FALLS WILL OVERSPREAD THE MID MS VLY AND OH/TN VLYS
DURING THE DAY ONE PERIOD...AS THE LONGWAVE RIDGE BUILDS IN THE
WESTERN CONUS WHILE AN UPPER LEVEL JET STREAK AND ASSOCIATED
SHORTWAVE OVER THE CENTRAL PLAINS EARLY THIS MORNING HELPS TO
CARVE OUT A LONGWAVE TROUGH ALONG AND EAST OF THE MS RIVER VALLEY.

THE SIGNAL REMAINS IN PLACE FOR A SYNOPTICALLY-DRIVEN HEAVY
RAINFALL EVENT...RELYING MAINLY ON THE ROBUST COOL-SEASON DYNAMICS
AND SUMMERTIME DEEP-LAYER MOISTURE PROFILES...WHEREAS THE STRONGER
INSTABILITY VALUES ARE NOT FORECAST TO COINCIDE WITH THE STRONGEST
FORCING. THUS SHORT TERM RAINFALL RATES (WITHIN 6 HOURS) ARE NOT
EXPECTED TO BE ESPECIALLY HEAVY IN THE MODERATE RISK AREA...BUT
PER MUCH OF THE MODEL GUIDANCE...MUCAPES OF 500-1000+ J/KG ARE
NOTED AS FAR NORTH AS THE I-70 CORRIDOR THIS AFTN AND EARLY
EVENING...WITH HIGHER CAPES FARTHER SOUTH. WPC THEREFORE FELT
COMFORTABLE TO TAKE A CONSENSUS APPROACH WITH THE QPF OVER THESE
AREAS...AS THE GLOBAL GUIDANCE CONTINUES TO GET SUPPORT FROM THE
HIGH-RES MODELS IN NOTING THE MAXIMUM QPF AXIS ALONG AND NORTH OF
THE OH RIVER WHERE THE DEEP-LAYER ELEVATED INSTABILITY...WHILE NOT
AS ROBUST AS COMPARED TO AREAS SOUTH...WILL NEVERTHELESS SUPPORT
AREAS OF HEAVY...POTENTIALLY EXCESSIVE RAINFALL GIVEN THE STRONG
DYNAMICAL FORCING. USING A MULTI-MODEL BLEND...WPC NOTED A RATHER
ELONGATED SWATH OF AREAL-AVERAGE RAINFALL BETWEEN 1-2.5 INCHES
ACROSS EASTERN PORTIONS OF THE MID MS VLY ACROSS THE OH VALLEY AND
INTO THE WESTERN SLOPES OF THE CENTRAL/NORTHERN APPALACHIANS.
HOWEVER...IT SHOULD BE NOTED THAT THE HIGH-RES GUIDANCE (INCLUDING
THE 4KM CONVECTIVE-ALLOWING MODELS) SHOW POCKETS OF HIGHER TOTALS
-- ON THE ORDER OF 3-5 INCHES.

A SLIGHT RISK OF EXCESSIVE RAINFALL SURROUNDS THE MODERATE RISK
AREA...AND REACHES FARTHER SOUTH INTO THE INSTABILITY AXIS WHICH
WILL BE SWEPT BY LOW LEVEL FORCING ALONG A FRONTAL BOUNDARY. FLOW
AT 850 MB IS STRONGLY VEERED...AND LACKS FOCUS...WHICH MAY LIMIT
CONVECTIVE ORGANIZATION AND TRAINING IN THE SLIGHT RISK AREA...AND
MAY EXPLAIN WHY THE HIGH RESOLUTION MODELS HAVE A MORE COHERENT
HEAVY RAIN SIGNAL FARTHER NORTH WITHIN THE DEEP LAYER FORCING. WPC
DID EXTEND THE RISK SOUTH AND EAST TO CATCH THE WARM
FRONT...RECENTLY ENHANCED BY CONVECTIVE OUTFLOWS...ACROSS SOUTHERN
VA AND EASTERN NC. DAYTIME HEATING SHOULD PROVE SUFFICIENT FOR
CONVECTIVE INITIATION GIVEN NEUTRAL UPPER FORCING...AND PW VALUES
ARE ESPECIALLY HIGH ALONG THIS PORTION OF THE FRONT. SOME SPOTS IN
VA/NC RECEIVED 2-3 INCHES OF RAIN ON THURSDAY.



...SOUTHERN ROCKIES AND SOUTHERN HIGH PLAINS...

HIGHLY-DIFFLUENT MID-UPPER LEVEL FLOW EAST OF THE UPPER RIDGE
ALONG WITH THE LOW-LEVEL FRONTAL BOUNDARY SLOWLY DROPPING SOUTH
ALONG THE EASTERN SLOPES OF THE SOUTHERN ROCKIES WILL PROVIDE
SUFFICIENT DYNAMICAL FORCING AND EASTERLY (UPSLOPE) LOW-LEVEL
MOISTURE TRANSPORT (AND ANOMALOUS PW VALUES) FOR MODERATE TO
LOCALLY HEAVY RAINFALL INTO THE SOUTHERN HIGH PLAINS AND ALONG THE
EASTERN SLOPES OF THE SOUTHERN ROCKIES. THE MODELS...PARTICULARLY
THE HIGH-RES GUIDANCE...ALL SHOW POCKETS OF HEAVIER TOTALS (1-3+")
ALONG THE EASTERN SLOPES OF THE SANGRE DE CRISTO MTNS OF
NM...WHICH WILL BE AIDED BY THE AVAILABLE DEEP-LAYER INSTBY WITH
MUCAPES BETWEEN 1000-1500 J/KG. CONSIDERING THE RELATIVELY LOW FFG
OVER THIS REGION (3 HOURLY VALUES AROUND 2.00 INCHES...6 HOURLY
AROUND 2.5 INCHES)...LOCALIZED RUNOFF ISSUES WILL BE LIKELY SHOULD
THESE AMOUNTS VERIFY.


...GULF COAST TO THE SOUTHEAST COAST...

THE MODELS ALL SHOW A SUBTLE MID/UPPER LEVEL SHEAR
AXIS...CURRENTLY ALONG THE CENTRAL-EASTERN GULF COAST PER WV AND
LONGWAVE IR SATELLITE LOOPS...EVENTUALLY BECOMING PICKED UP BY THE
AMPLIFYING TROUGH AND SCOOTING OFF THE SOUTHEAST (GA/SC) COAST
OVERNIGHT FRI-SAT. CONSIDERING THE DEGREE OF THERMODYNAMICS IN
PLACE (PWATS 2.00-2.25" AND MUCAPES 1500-2500+ J/KG)...EXPECT
POCKETS OF HEAVY SHOWERS/TSTMS...PARTICULARLY DURING PEAK HEATING
WITH INTERACTION OF GULF/SEA BREEZE BOUNDARIES. THE CONSENSUS
AMONG THE HIGH-RES MODELS IS FOR A LOCAL MAXIMA IN QPF (1-2+
INCHES) ALONG THE GULF COAST OVER THE WESTERN FL PANHANDLE AS WELL
AS OVER FAR SOUTHEAST GA AND EXTREME NORTHEAST FL.

GRAPHICS AVAILABLE ON THE WEB AT WWW.WPC.NCEP.NOAA.GOV

HURLEY/BURKE
$$





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