Quantitative Precipitation Forecast
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FOUS30 KWBC 261451
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1050 AM EDT FRI JUN 26 2015

...VALID 15Z 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
10 SE TDZ 15 SSW HZY DUJ 25 S UNV HGR OKV 25 W CJR 15 E PTB
20 SSE EDE NKT 15 S NCA 15 S DPL 15 ESE RDU 20 S ROA 30 E JKL
20 SW BWG 35 NW HOP 10 SSE MVN 15 NW SET 15 SSW UIN 15 WSW MQB
20 ESE PNT 10 SE TDZ.

MODERATE RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 S LHQ 45 WSW UNI 30 S CVG 10 SE LWV 20 ESE PPQ 20 NNE PPQ
20 N IJX 20 S BMI 15 S LAF AID 15 WNW TZR 20 S LHQ.


DAY 1

...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.


...SOUTHWEST MISSOURI AND ADJACENT KS/OK/AR...

A SHORT TERM THREAT OF HEAVY RAINFALL IS EXPECTED THROUGH ABOUT
18Z...MAINLY FOCUSED ON SOUTHWEST MISSOURI. WEST TO SOUTHWESTERLY
850-700 MB FLOW WILL FEED WEAKLY UNSTABLE AIR OVER OUTFLOW
BOUNDARIES TO YIELD SMALL SWATHS OF ADDITIONAL RAINFALL AVERAGING
JUST UNDER ONE INCH PER HOUR. WITH REPEATED ACTIVITY OVER
SOUTHWEST MISSOURI ISOLATED ADDITIONAL FLASH FLOODING MAY OCCUR.
OTHERWISE...RAIN RATES ARE EXPECTED TO INCREASE WITHIN NEW
AFTERNOON CONVECTION IN OK/AR...BUT VEERING FLOW AND GREATER
TEMP/DEWPOINT DEPRESSIONS SHOULD PRODUCE A PROGRESSIVE EVENT WITH
RELATIVELY LITTLE TRAINING.


...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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