Quantitative Precipitation Forecast
Issued by NWS

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000
FOUS30 KWBC 170040
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
740 PM EST THU FEB 16 2017

...VALID 01Z FRI FEB 17 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
80 WSW 87Q 20 SW PRB 15 ENE PRB 45 ENE SBP 40 WSW BFL 15 N CMA
25 WSW OXR 45 S SBA 70 S LPC 75 SSW LPC.


0100 UTC UPDATE

REMOVED MARGINAL RISK AREA ACRS NW CA AS MAIN BAROCLINIC BAND
CONTINUES TO SETTLE SWD TOWARD SRN CA.  FOR THE REMAINDER OF THE
NIGHT...SHOULD SEE AN INCREASING HEAVY RAIN THREAT TOWARD 12Z HAS
SATL IMAGERY SHOWS ENHANCEMENT OF ATMOSPHERIC RIVER PLUME NEAR AND
WEST OF 130W IN RESPONSE TO UPSTREAM S/WV ENERGY PUSHING EAST OF
140W AS OF 00Z.  MODELS CONTINUE TO FCST STRENGTHENING OF SWLY 85H
SWLY FLOW TO NEAR 40 KTS BY MRNG ALONG AXIS OF STALLED FRONTAL
BNDRY INVOF POINT CONCEPTION WHICH ALONG WITH PWS FCST TO BE AOA
1.25 INCHES...WILL PROVIDED VERY ANOMALOUS MSTR FLUX VALUES INTO
THE COAST.  WHILE THE MAIN HEAVY RAIN THREAT WILL OCCUR AFTER THIS
PD...SOME LOCAL 1 TO 1.5" RAINS MAY OCCUR ACRS SOME OF THE MORE
FAVORED COASTAL RANGES NEAR AND SOUTH OF POINT CONCEPTION BY MRNG
WHICH COULD LEAD TO ISOLD RUNOFF ISSUES ESPECIALLY IN BURN SCAR
AREAS.

SULLIVAN

...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
CHANNELED 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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