Quantitative Precipitation Forecast
Issued by NWS

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FOUS30 KWBC 090109
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
908 PM EDT TUE JUL 08 2014

...VALID 03Z WED JUL 09 2014 - 00Z THU JUL 10 2014...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...



AR EWD INTO THE TN VALLEY

SOME CONCERN EXISTS FOR POTNL TRAINING OF STORMS ACRS PARTS OF AR
EWD INTO TN/NRN AL/NRN MS OVERNIGHT AS VERY MOIST 85H WLY FLOW AND
POOLING OF 1.75 TO GREATER THAN 2 INCH PWS HELPS SUPPORT SOME STGR
ORGANIZED TSTM CLUSTERS THAT WILL TEND TO REGENERATE UPSTREAM AND
TRACK EWD ACRS THE REGION TO THE SOUTH OF SLOW MOVING COLD FRONT.
WHILE SOME MODEST SPREAD EXISTS IN PLACEMENT OF HEAVIEST
RAINS...MANY OF THE 12Z HI RES RUNS SUGGEST PONTL FOR 1 TO 3 INCH
RAINS WITH ISOLD AMOUNTS IN EXCESS OF 5 INCHES.   LATEST FEW RUNS
OF THE HRRR SHOWED CONSIDERABLE SPREAD WITH LOCATION AND VOLUME OF
THE HEAVIEST AMOUNTS...AND GIVEN LACK OF DECENT RUN TO RUN
CONSISTENCY HAVE NOT HIGHLIGHTED A SLIGHT RISK AT THIS
TIME..THOUGH POTNL FOR ISOLD RUNOFF PROBLEMS SEEMS REASONABLE.


SOUTHWESTERN U.S. INTO THE GREAT BASIN

WATER VAPOR SHOWS A MOISTURE PLUME STREAMING ACROSS NORTHWEST
MEXICO INTO AZ/UT/CO/ADJACENT NM.  THE LATEST MODELS ARE IN GOOD
AGREEMENT IN KEEPING THE MEAN MID-UPPER HIGH HEIGHTS CENTERED OVER
THE GREAT BASIN.  WEAK IMPULSES REMAIN EMBEDDED WITHIN AND ON THE
PERIPHERY OF THE MEAN ANTICYCLONE.  MUCH ABOVE AVERAGE PW VALUES
WITH STANDARD DEVIATIONS OF 2-3+ ABOVE THE MEAN WILL PERSIST FROM
THE SOUTHWEST INTO THE GREAT BASIN.  THESE HIGH PW VALUES AND THE
PERSISTENT UPPER SHEAR AXIS WITH EMBEDDED VORTS
AND UPPER DIVERGENCE MAXIMA WILL SUPPORT ANOTHER DAY OF WIDELY
SCATTERED MONSOONAL CONVECTION.  DUE TO HIGH AVAILABLE
MOISTURE...THERE IS POTENTIAL FOR ADDITIONAL ISOLATED RUNOFF
ISSUES.  FORECAST CONFIDENCE IS LOW WITH RESPECT TO DETAILS OF
WHERE HEAVIEST PRECIPITATION TOTALS WILL OCCUR...AS THE MODELS
SHOW SPOTTY SHOWERS/STORMS WITH QPF ON THE ORDER OF QUARTER TO
HALF AN INCH.
HIGHER LOCAL MAXIMA ARE EXPECTED WHERE CELLS ARE SLOW TO MOVE IN
THE LIGHT FLOW ENVIRONMENT...AS FCST WINDS BELOW 500 MB DROP TO 10
KT OR LESS LATE TONIGHT INTO WED.

SULLIVAN
$$




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