Quantitative Precipitation Forecast
Issued by NWS

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FOUS30 KWBC 251835
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
234 PM EDT FRI JUL 25 2014

...VALID 18Z FRI JUL 25 2014 - 00Z SUN JUL 27 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.


...SOUTH CAROLINA...

SLOW MOVING CONVECTION HAD BROKEN OUT BY MIDDAY AHEAD OF A SLOW
MOVING FRONTAL BOUNDARY. AN 18Z MESOANALYIS INDICATED MIXED LAYER
CAPE OF 1500-2000 J/KG WITHIN WITHIN A VERY MOIST ENVIRONMENT...PW
OF 1.92 INCHES SAMPLED BY THE MORNING RAOB AT CHARLESTON. WITH A
500 MB TROUGH AXIS HANGING BACK TO THE WEST AND SWEEPING ACROSS
CENTRAL/EASTERN SC THIS AFTERNOON...SOME ORGANIZED STORM MODES ARE
EXPECTED WITH REDEVELOPMENT/TRAINING ALONG OUTFLOWS. HEATING MAY
ERODE AN AREA OF LOW CLOUDS NEAR/BEHIND THE FRONT...ALLOWING SOME
NORTHWARD DEVELOPMENT OF NEW CONVECTION...WHILE THE EVENT AS A
WHOLE PROPAGATES GENERALLY SOUTH OVER TIME. 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.


...COLORADO...

A PLUME OF MOISTURE WITHIN THE RIDGE WAS PIVOTING AROUND WESTERN
COLORADO AS INCREASED WESTERLY MID LEVEL FLOW TOPPED THE RIDGE.
STRONG HEATING AND PLACEMENT OF THE PLUME IS LIKELY TO YIELD
INITIATION OF SCATTERED TO NUMEROUS THUNDERSTORMS... GREATEST
COVERAGE BEING IN CENTRAL AND WESTERN COLORADO. WINDS IN THE CLOUD
BEARING LAYER...AND NEAR CLOUD BASE...WILL DECREASE THROUGH THE
AFTERNOON AS A 700-600 MB WAVE EXITS INTO EASTERN COLORADO. CAPE
IS ALSO SLIGHTLY LESS THAN SEEN YESTERDAY. THE RESULT MAY BE MORE
OUTFLOW DOMINANCE AND RAIN RATES NOT QUITE AS HIGH AS
YESTERDAY...ALTHOUGH INSTANTANEOUS RATES NEARING AN INCH PER HOUR
COULD PRODUCE ISOLATED FLASH FLOODING IN PARTICULARLY SUSCEPTIBLE
TERRAIN/BASINS.


...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 ACROSS NORTHWEST AZ AND ADJACENT
STATES...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
FARLY 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. FARTHER SOUTH...THE MODELS HAVE BECOME MORE
AGGRESSIVE IN THE COVERAGE AND INTENSITY OF PRECIPITATION
EMANATING FROM THE MOUNTAINS AROUND TUSCON...ALTHOUGH CELL MOTIONS
AWAY FROM THE UNSTABLE INFLOW COULD LIMIT THE POTENTIAL FOR
TRAINING.

BURKE
$$





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