Quantitative Precipitation Forecast
Issued by NWS

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000
FOUS30 KWBC 211743
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
143 PM EDT TUE OCT 21 2014

...VALID 18Z TUE OCT 21 2014 - 00Z THU OCT 23 2014...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


...PACIFIC NORTHWEST...

THE LATEST IR/WV SAT IMAGERY INDICATES A MOIST AND STRONG
TRANS-PACIFIC JET POSITIONED UNDERNEATH A WELL-DEFINED GULF OF AK
VORTEX ATTM. THE JET ENERGY IS AIMING FOR THE PACIFIC NORTHWEST IN
CONJUNCTION WITH A COLD FRONT...AND THIS COUPLED WITH A
SUBTROPICAL CONNECTION TO THE DEEPER LAYER MOISTURE
PLUME/ATMOSPHERIC RIVER...IT IS EXPECTED THAT VERY HVY RAINS WILL
IMPACT THE NORTHWEST AND ESPECIALLY THE THE COASTAL RANGES OF
WA/OR AND INTO THE CASCADES. IN FACT...THE 00Z ECMWF INDICATES A
50 TO 60 KT SWLY H50 JET AIMED INTO THE OLYMPIC PENINSULA LATER
TONIGHT AND INTO EARLY WED JUST AHEAD OF THE COLD FRONT. THE 12Z
GFS INDICATES MOISTURE FLUX ANOMALIES OF 4 TO 5 STD DEV ABOVE
NORMAL AIMED INTO SWRN WA AND WRN OR AT 12Z ON WED. THE DEEP
MOISTURE TRANSPORT COUPLED WITH OROGRAPHICS AND LARGE SCALE ASCENT
WITH THE COLD FRONT AND SUPPORTING SHORTWAVE DYNAMICS SHOULD YIELD
RAINFALL AMTS THROUGH LATE WED OF 2 TO 4 INCHES FOR THE WA/OR
COASTAL RANGES AND INTO THE CASCADES...HOWEVER HEAVIER AMTS
LOCALLY EXCEEDING 5 INCHES ARE ANTICIPATED ESP FOR THE OLYMPIC
PENINSULA AND THE NRN WA CASCADES WHERE STRONGER MOISTURE
TRANSPORT/UPSLOPE IS EXPECTED. THESE RAINFALL AMTS ARE LIKELY TO
CAUSE SOME RUNOFF/FLOODING PROBLEMS OF A LONGER TERM NATURE...AS
OPPOSED TO SHORT-TERM FLASH FLOODING GIVEN THE EXPECTED DURATION
OF THIS NEXT EVENT.

ORRISON
$$





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