Quantitative Precipitation Forecast
Issued by NWS

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FOUS30 KWBC 160827
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
326 AM EST THU FEB 16 2017

...VALID 12Z THU FEB 16 2017 - 12Z FRI FEB 17 2017...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
70 W CEC 60 NW CEC 55 NNW CEC 45 W SXT 35 WSW SXT 30 WSW SXT
35 ENE CEC 25 NE ACV 25 E ACV 30 WNW O54 15 W O54 25 ENE O54
20 S MHS 20 E RDD 30 NNE CIC 30 NE OVE 20 E AUN 50 SSW TVL
45 NE MOD 20 E MHR BAB 10 N CIC 10 ENE RBL 25 SSE O54 25 NNE O87
25 W O87 70 W O87.

MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
75 W MRY 65 SW SFO 20 W SFO SFO 10 SSE RHV WVI 10 NW SNS
30 SSE SNS 15 N PRB 30 E PRB 40 WSW BFL 20 ENE SBA 25 WSW OXR
45 S SBA 70 S LPC 75 SSW LPC.


...CALIFORNIA AND EXTREME SW OREGON...

RECENT MODELS AND ENSEMBLES CONTINUE TO OFFER QUITE RUN TO RUN
CONSISTENT AND WELL CLUSTERED MASS FIELD AND QPF GUIDANCE THROUGH
THIS PERIOD. LATEST BLENDED TPW LOOPS SHOW A LONG FETCH
ATMOSPHERIC RIVER EXTENDING SOUTHWESTWARD FROM COASTAL PACIFIC NW
TO HAWAII AND BEYOND ACROSS THE TROPICAL W-CENTRAL PACIFIC. WELL
CHANNELLED DEEP MOISTURE IS ALREADY SUPPORTING SOME .3" TO .4"
HOURLY RAINFALL RATES THAT ONSHORE WITH FAVORED TOPOGRAPHY COULD
SWELL TO NEAR 1"/HOUR. THIS ACTIVITY WOULD BE FURTHER MAINTAINED
BY WAVE INDUCEMENT NOW INDICATED OFF THE NRN CA COAST AS INDUCED
WITH APPROACH OF FURTHER OFFSHORE POTENT SHORTWAVE TROUGH/LOW.
WIDESPREAD PRECIPITATION SPREAD SOUTH FROM THE PACIFIC NORTHWEST
AND NRN CA TONIGHT WILL CONTINUE TO SINK SOUTHWARD THROUGH CENTRAL
THEN SRN CALIFORNIA AS HEIGHTS LOWER ACROSS CA AND NWRN STATES.
THIS OCCURS CONCURRENT WITH AN AXIS OF MUCH ABOVE PW VALUES OF 2
TO 3 STANDARD DEVIATIONS ABOVE THE MEAN IN THE AXIS OF STRONGEST
SOUTH SOUTHWESTERLY LOWER LEVEL FLOW. THE ANOMALOUS PW VALUES AND
CORRESPONDING ANOMALOUS 850-700 MB MOISTURE FLUX VALUES WILL
SUPPORT WIDESPREAD HEAVY PRECIP POTENTIAL. THE MARGINAL THREAT
AREA ACROSS EXTREME SW OREGON/NRN CA IS SLATED FOR CONTINUING
ACTIVITY INTO THE FIRST PORTION OF THIS FORECAST PERIOD. BUILDING
ACTIVITY ACROSS S-CENTRAL CA COASTAL AREAS IS MORE ON TAP FOR THE
LATTER PART OF THIS PERIOD AS FLOW/SUPPORT PUNCH INTO THE COAST
EARLY FRIDAY MORNING TO SOAK THESE AREAS IN ADVANCE OF AN
ADDITIONAL/AMPLE DAY 2 RUNOFF THREAT. FORECAST CONFIDENCE REMAINS
HIGH THIS PERIOD FOR THE WIDESPREAD HEAVY PRECIP POTENTIAL
CONSIDERING LOW MODEL SPREAD.

SCHICHTEL
$$





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