Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000
FXUS66 KSEW 172227
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
226 PM PST MON NOV 17 2014

.SYNOPSIS...AN OFFSHORE UPPER RIDGE WILL BRING ANOTHER CLEAR COLD
NIGHT TONIGHT. THE RIDGE WILL MOVE SLOWLY INLAND TUESDAY AND
WEDNESDAY FOR GRADUALLY INCREASING CLOUDS. PRECIPITATION WILL RETURN
TO WESTERN WASHINGTON WEDNESDAY NIGHT OR THURSDAY AS A WEAK FRONT
ARRIVES. A STRONGER FRONTAL SYSTEM SHOULD ARRIVE FRIDAY...WITH
GENERALLY WET WEATHER FOR THE WEEKEND.

&&

.SHORT TERM...MOSTLY CLEAR SKIES WITH A FEW WISPY CIRRUS CLOUDS
OVER WESTERN WASHINGTON THIS AFTERNOON WITH TEMPERATURES GENERALLY 1
TO 4 DEGREES WARMER THAN YESTERDAY. HIGH AMPLITUDE RIDGING WILL
REMAIN IN PLACE FOR ANOTHER NIGHT...BRINGING CLEAR SKIES AND COLD
TEMPS AGAIN TONIGHT.

12Z MODELS REMAIN FAIRLY CONSISTENT WITH REGARD TO THE SLOW EASTWARD
TREK OF THE RIDGE. CLOUDS EXPECTED TO INCREASE SLOWLY THROUGH THE
DAY TOMORROW AND INTO WEDNESDAY MORNING BEFORE WE START TO SEE THE
FIRST SIGNS OF PRECIP LATE WEDS AFTERNOON ALONG THE COAST...LATER IN
THE EVENING INLAND. 12Z GFS PUTS RAIN AT THE COAST AROUND 18Z WEDS
AND INLAND BY 00Z...WHEREAS ECMWF TRENDS SLOWER BY 6 HOURS.
INHERITED FORECAST COMPROMISED BETWEEN THE TWO AND SAW NO REASON TO
DEVIATE FROM THAT THINKING. THUS...INHERITED FORECAST REMAINS
LARGELY UNCHANGED. THIS SYSTEM WILL LINGER INTO THURSDAY BEFORE RAIN
BEGINS TO TAPER OFF THURSDAY EVENING. SMR

.LONG TERM...SYSTEM MOVING IN FOR LATE FRIDAY MORNING LOOKS TO HAVE
MUCH BETTER ZONAL FLOW AND MARKS THE BEGINNING OF A WET PATTERN FOR
WESTERN WASHINGTON...WITH A FIRST ROUND OF SHOWERS KICKING IN FOR
MUCH OF THE CWA BY EARLY AFTERNOON FRIDAY AND EXTENDING THROUGH
SATURDAY. THAT SAID...HAVE BUMPED POPS UP A BIT TO REFLECT BETTER
AGREEMENT BETWEEN MODELS. A SERIES OF SHORTWAVE DISTURBANCES WILL
KEEP RAIN IN THE FORECAST FOR THE REMAINDER OF THE WEEKEND. LOW
PRESSURE OFF THE GULF OF ALASKA LOOKS TO SEND ANOTHER WAVE OF
MOISTURE FOR THE START OF NEXT WEEK. SMR

&&

.HYDROLOGY...RIVER FLOODING IS NOT EXPECTED IN THE NEXT 7 DAYS.

&&

.AVIATION...A STRONG UPPER LEVEL RIDGE WILL REMAIN OVER W WA THROUGH
TUESDAY NIGHT. A SURFACE RIDGE OVER E WA WILL MAINTAIN DRY EASTERLY
LOW LEVEL OFFSHORE FLOW. THE AIR MASS WILL REMAIN DRY AND STABLE
WITH UNRESTRICTED VFR CONDITIONS EXPECTED. THERE COULD BE SOME
PATCHY SHALLOW EARLY MORNING FOG IN VALLEYS AND OVER THE SW
INTERIOR...BUT IF IT OCCURS IT WILL BE BRIEF.

KSEA...CLEAR WITH UNRESTRICTED VISIBILITY THROUGH TUESDAY NIGHT.
OVERALL...SURFACE WINDS WILL BE PRETTY LIGHT...FAVORING NORTH 3-7 KT
THROUGH 01Z THEN SHIFT EASTERLY 3-7 KT. KAM

&&

.MARINE...THE SURFACE RIDGE OVER E WA...COMBINED WITH LOWER PRESSURE
OVER THE NE PACIFIC FROM AN UPPER LEVEL TROUGH...WILL MAINTAIN
EASTERLY FLOW ACROSS W WA THROUGH WEDNESDAY MORNING. A WEAK COLD
FRONT WILL APPROACH FROM THE SW ON WEDNESDAY...THEN MOVE NE ACROSS
THE AREA WEDNESDAY NIGHT. MODERATE SE FLOW SHOULD DEVELOP WITH SCA
WINDS EXPECTED OVER THE COASTAL WATERS AND THE NORTHERN INTERIOR
WATERS. A WEAKER FRONT WILL REACH THE AREA THURSDAY. A STRONGER
FRONTAL SYSTEM ARRIVING FROM THE W ON FRIDAY COULD GENERATE S-SE
GALES OVER THE COASTAL AND NORTHERN INTERIOR WATERS. KAM

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY WEST ENTRANCE TO THE STRAIT AND COASTAL
      ZONE PZZ150.

&&

$$

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