Quantitative Precipitation Forecast
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000
FOUS30 KWBC 190700
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
259 AM EDT TUE AUG 19 2014

...VALID 06Z TUE AUG 19 2014 - 12Z 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
15 NNE DPG 25 SW CMS 25 ENE VEL 45 NE PGA 60 E GCN 30 S SJN
40 E DUG 135 SSE DUG 85 E MMHO 45 N MMHO 55 SSW CGZ 50 SE EED
30 NNW IFP 50 S ELY 15 NNE DPG.


...CENTRAL/SOUTH-CENTRAL TX...

A COMPACT...QUASI-STATIONARY MID LEVEL CIRCULATION ACROSS
CENTRAL/SOUTH-CENTRAL TX WILL CONTINUE TO DRIFT THIS MORNING
UNDERNEATH THE BROAD UPPER RIDGE. DYNAMICAL SUPPORT AFFORDED BY
THE CONVECTIVELY-ENHANCED VORT MAX IS ALLOWING FOR THE WIDESPREAD
DEVELOPMENT OF SHOWERS AND TSTMS ACROSS CEN/SOUTH-CEN TEXAS EARLY
THIS MORNING...WITH THE ACTIVITY AIDED BY A FAVORABLE
THERMODYNAMIC ENVIRONMENT WITH PWATS NEAR 2.00 INCHES...MUCAPES
AOA 1000 J/KG...AND ELEVATED LLVL SOUTHERLY INFLOW AROUND 30 KTS.
THE RELATIVELY STRONG SOUTHERLY LLVL FLOW JUXTAPOSED WITH THE WEAK
CYCLONIC STEERING FLOW (MEAN WIND) WILL CONTINUE TO ALLOW FOR SLOW
MOVING/NEARLY STATIONARY STORM MOTION AND TRAINING OF CONVECTION.
THE MESOSCALE GUIDANCE -- WHICH STILL APPEARS TO BE PLACING THIS
ACTIVITY WAY TOO FAR TO THE NORTH -- IS GENERATING LOCAL AMOUNTS
OF 3-5". CONSIDERING THE SATURATED SOILS...ADDITIONAL RUNOFF
ISSUES AND LOCALIZED FLASH FLOODING IS LIKELY THROUGH
DAYBREAK...AFTER WHICH TIME THE LLVL INFLOW WILL WEAKEN.


...SOUTHWEST INTO THE GREAT BASIN...

ABOVE AVERAGE PW VALUES -- 1.5 TO 2 STANDARD DEVIATIONS ABOVE THE
MEAN -- WILL CONTINUE TO BE FUNNELED NORTH-NORTHEASTWARD THIS
PERIOD ACROSS THE SOUTHWEST INTO THE GREAT BASIN BETWEEN THE
CLOSED LOW DIVING SOUTHWARD INTO CEN-SRN CALIFORNIA AND THE UPPER
HIGH THAT WILL SHIFT SLOWLY FROM THE ROCKIES INTO THE PLAINS. VERY
DIFFLUENT UPPER FLOW EXPECTED AHEAD OF THIS CLOSED LOW...WITH A
BROAD AREA OF DIVERGENCE ALOFT NOTED FROM THE MODELS OVER THE
OUTLOOK AREA BETWEEN THE HIGHLY AMPLIFIED TROUGH/RIDGE AXES.
MOREOVER...THE MODELS CONTINUE TO DEPICT WELL-DEFINED
CONVECTIVELY-ENHANCED VORTS OR MCVS  MOVING NORTH-NORTHEASTWARD IN
THE HIGH PW AXIS. THIS WILL SUPPORT NUMEROUS DIURNALLY-AIDED
SHOWERS/TSTMS DURING THE PERIOD FROM THE SOUTHWEST INTO THE GREAT
BASIN...WITH THE MODEL CONSENSUS AGAIN SUPPORTING MODERATE TO
HEAVY RAINFALL TOTALS...ALONG WITH THE ENHANCED RISK FOR LOCALIZED
RUNOFF ISSUES AND FLASH FLOODING. SOME OF THE HIGHER RESOLUTION
GUIDANCE...PARTICULARLY THE 4KM WRF-ARW AND NAM CONEST...WERE
UTILIZED FOR THE QPF DETAILS THIS PERIOD... ALONG WITH THE
IN-HOUSE PSEUDO BIAS CORRECTED ENSEMBLE MEAN.


...UPPER MIDWEST INTO THE UPPER GREAT LAKES REGION...

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 TODAY. THE 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 NUMEROUS
SHOWERS/TSTMS FROM EASTERN PORTIONS OF THE THE UPPER MS VALLEY
(WI) INTO THE UPPER LAKES...AND EVENTUALLY SOUTHWARD ALONG THE
TRAILING COLD FRONT INTO THE MID MS VALLEY. CONFIDENCE NOT GREAT
WITH DETAILS..HOWEVER CONFIDENCE REMAINS HIGH THAT THERE WILL BE
MODERATE TO LOCALLY HEAVY RAINFALL TOTALS GIVEN THE ABOVE
DYNAMICS/MOISTURE.  THE HIGH RESOLUTION GUIDANCE (WRF-ARW...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"+ WILL BE POSSIBLE.

HURLEY
$$





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