Quantitative Precipitation Forecast
Issued by NWS

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000
FOUS30 KWBC 251330
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
929 AM EDT FRI JUL 25 2014

...VALID 15Z FRI JUL 25 2014 - 12Z SAT JUL 26 2014...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
55 SE CHS 25 ESE HXD 20 NNE SAV 35 NNE JYL 20 SSW CAE 20 N MMT
10 N FLO 10 SSE CRE 55 SE CHS.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
10 SSW ALO 20 SSW VTI 20 WSW IOW 20 NE OTM 15 NW OTM 15 SW TNU
15 WNW BNW 25 WNW FOD 20 W AXA 15 N AXA 10 W MCW 20 WNW ALO
10 SSW ALO.


...SOUTH CAROLINA...

ALONG A SLOW MOVING FRONTAL BOUNDARY...HIGH RESOLUTION MODELS ARE
SENDING A CONSISTENT MESSAGE OF HEAVY RAIN POTENTIAL SURROUNDING A
WEAK LOW THAT THE RAP FORMS NEAR MYRTLE BEACH THIS MORNING AND
THEN STEERS INLAND DURING THE AFTERNOON. HEATING INTO THE UPPER
80S/LOWER 90S WILL YIELD MIXED LAYER CAPE VALUES OF AROUND 2000
J/KG WITHIN A VERY MOIST ENVIRONMENT...PW OF 1.92 INCHES SAMPLED
BY THE MORNING RAOB AT CHARLESTON. WITH A 500 MB TROUGH AXIS
HAVING BACK TO THE WEST AND SWEEPING ACROSS CENTRAL/EASTERN SC
THIS AFTERNOON...THERE IS REASON TO BELIEVE THAT MID LEVEL ASCENT
AND AMPLE SHEAR PROFILES WILL LEAD TO SOME ORGANIZED STORM MODES
AND REDEVELOPMENT/TRAINING ALONG OUTFLOWS. FLASH FLOOD GUIDANCE
VALUES ARE HIGH IN THIS AREA...AS IS TYPICAL...BUT INTENSE RAIN
RATES AND PERIODS OF TRAINING ECHOES EXPERIENCED LOCALLY MAY YIELD
ISOLATED 2.5 TO 3 INCH RAIN AMOUNTS OVER 1-3 HOURS...AND AT LEAST
A THREAT OF FLASH FLOODING.


...IOWA...

A RISK OF FLASH FLOODING IS FORECAST TO CONTINUE IN THE SHORT
TERM...AND OVER A SMALL PART OF CENTRAL IOWA...OWING TO ONGOING
CONVECTION ALIGNED WHERE LOCAL 2-3 INCH AMOUNTS MAY HAVE ALREADY
FALLEN FROM NE THROUGH SE OF DES MOINES. MODELS SHOW MID LEVEL
ASCENT WANING THROUGH THE MORNING AS A SUBTLE SHORTWAVE MOVES OUT
OF NORTHERN IOWA...BUT MODELS HAVE NOT HANDLED THIS EVENT
PARTICULARLY WELL...AND THE ESTABLISHED COLD POOL COULD SUSTAIN
RENEWED UPDRAFTS FOR A FEW HOURS LONGER THAN MODELED...ESPECIALLY
GIVEN CONTINUED SOUTHWESTERLY INFLOW FROM AN UNSTABLE SOURCE
REGION. ULTIMATELY...SYNOPTIC SCALE ADVECTION OF WARMER MID LEVEL
TEMPERATURES AND PROGRESSION OF AN 850-700 MB TROUGH DOWNSTREAM
INTO MORE STABLE AIR SHOULD CAUSE THE CONVECTION TO SHRINK BY THIS
AFTERNOON.


...COLORADO...

MOISTURE WITHIN THE RIDGE AND WEST OF THE RIDGE CENTER WHICH GOT
DRAWN INTO PARTS OF UTAH/COLORADO ON THURSDAY WILL STILL BE IN
PLAY TODAY AS THE FLOW PATTERN WILL NOT HAVE CHANGED MUCH AND A
PLUME OF HIGHER PRECIPITABLE WATER VALUES WILL BE CONTINUE TO
ROTATE AROUND THE WESTERN PERIPHERY OF THE RIDGE INTO SOUTHERN UT
AND WESTERN CO.  00Z MODELS CONTINUED THE IDEA THAT CAPE VALUES
MAY NOT BE QUITE AS HIGH AND THE MID LEVEL ASCENT IS NOT QUITE AS
FOCUSED AS ON THU.


...FAR SOUTHWEST U.S...

FORECASTS FROM THE RAP AND THE GLOBAL SCALE MODELS INDICATE A
PLUME OF ENHANCED MID LEVEL MOISTURE WILL ADVECT THROUGH THE LOW
DESERT IN WESTERN AZ/SOUTHERN CA TODAY...REACHING THE MOUNTAINOUS
TERRAIN BETWEEN FLAGSTAFF...LAS VEGAS...AND NORTHWEST OF NEEDLES
BY AFTERNOON. THE 12Z TUSCON SOUNDING MAY BE MOST REPRESENTATIVE
OF THIS ENVIRONMENT. INSTABILITY SHOULD BE SUFFICIENT TO SUPPORT
DIURNAL THUNDERSTORMS...AND ENHANCED 850-700 MB SOUTHERLY FLOW OF
15-25 KNOTS AROUND THE PERIPHERY OF THE MID LEVEL RIDGE MAY LEND
SOME ORGANIZATION TO THE CONVECTION ON A LOCAL SCALE...ALLOWING
FOR SOME REDEVELOPMENT ALONG OUTFLOWS. TEMP/DEWPOINT SPREADS
REMAIN FAILY LARGE...HOWEVER...AND THE QPF SIGNAL FROM THE HIGH
RESOLUTION GUIDANCE IS SPOTTY AND SMALL SCALE...SUGGESTING PERHAPS
A VERY ISOLATED FLASH FLOOD RISK IN THE MOST SUSCEPTIBLE TERRAIN
AND/OR WATER CHANNELS.

BURKE/BANN
$$




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