Gale Warning 74, NWS Seattle, WA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 PM PST WED DEC 10 2008

.SYNOPSIS...AN UPPER LEVEL RIDGE WILL BUILD THURSDAY...AND AFTER
MORNING CLOUDS SKIES SKIES WILL PARTIALLY CLEAR. A STRONG LOW
PRESSURE SYSTEM WILL CROSS WESTERN WASHINGTON ON FRIDAY...BRINGING
MUCH COOLER AIR. RAIN...WIND...AND MOUNTAIN SNOW WILL ACCOMPANY THE
SYSTEM THROUGH SATURDAY. COLDER AIR ON FRIDAY NIGHT WILL BRING THE
THREAT OF SNOW TO SEA LEVEL. SNOW SHOWERS COULD CONTINUE SUNDAY.

&&

.SHORT TERM...NOT MUCH GOING ON IN THE SHORT TERM. RADAR IS BLANK...
SKIES ARE CLOUDY...TEMPERATURES ARE HANGING IN THE 40S. THIS PATTERN
WILL CONTINUE THURSDAY. UPPER RIDGING IS IN FAVOR...BUT WEAK TO
NONEXISTENT SURFACE GRADIENTS ARE AGAINST...THE IDEA OF SOME
AFTERNOON CLEARING ON THURSDAY. JUST HAVE TO SEE.

MORE INTERESTING WEATHER IS DUE FRIDAY. GFS 00Z VERSION HAS
ESSENTIALLY THE SAME TRACK AS THE 18Z RUN. A DEEP LOW...984 MB...
MOVES EAST DOWN THE STRAIT OF JUAN DE FUCA. BY 00Z SATURDAY IT IS
OVER KCLM AND BY 12Z IT IS IN EASTERN WASHINGTON. AT THE SAME TIME A
SUB-520 DM HEIGHT UPPER LOW MOVES ACROSS THE STATE. MOST OF THE
PRESSURE GRADIENT WITH THIS STORM IS OVER OREGON. THIS IS ALL 48
HOURS OR SO AWAY AND CONTINUING THE HIGH WIND WATCH AND GALE WATCHES
ETC IS APPROPRIATE.

IF THERE IS STRONG WIND IT WILL HAVE AN ONSHORE COMPONENT AND COULD
VERY WELL KEEP CONDITIONS TOO WARM FOR SNOW FRIDAY AND FRIDAY NIGHT.
POST FRONTAL IT IS A DIFFERENT STORY...COLD AIR SLIPS IN FROM CANADA
AND SHOWERS ON SATURDAY ARE LIKELY TO HAVE SOME SNOW IN THEM. BURKE

.LONG TERM...PREVIOUS DISCUSSION...ECMWF/GFS BOTH BRING DOWN AN
UPPER LOW ON SUNDAY OFF THE WASHINGTON COAST. WITH COLD AIR ALREADY
IN PLACE BOTH MODELS SPREAD SNOW OVER THE WESTERN PORTION OF THE
OLYMPIC PENINSULA. EASTERLY OFFSHORE WOULD AID IN SQUEEZING MOISTURE
THE EASTERN SIDE OF THE OLYMPICS FOR THE HOOD CANAL AND ALONG THE
STRAIT OF JUAN DE FUCA. BREEZY TO WINDY CONDITIONS WOULD ALSO EXIST
DEPENDING ON OFFSHORE GRADIENTS FOR THE PASSES AND NORTHERN
INTERIOR. SOME OF THE COLDEST AIR WILL FILTER SUNDAY NIGHT THROUGH
MONDAY...WITH DAYTIME HIGHS STRUGGLING TO REACH FREEZING AND LOWS IN
THE UPPER TEENS AND LOW TWENTIES. BELLINGHAM AND LOCATIONS ALONG THE
NORTHERN INTERIOR WILL BE EVEN COLDER WITH THEIR PROXIMITY TO FRASER
VALLEY. HIGH PRES BUILDS IN MONDAY FOR DRIER WEATHER...BUT THE
PATTERN STAYS COLD THROUGH EARLY MIDWEEK.  LOOKS LIKE THIS WILL BE A
PRETTY INTERESTING WEEK. DAMICO

&&

.AVIATION...RIDGING AT THE SURFACE AND ALOFT REMAINS OVER THE REGION
THIS EVENING. THIS PATTERN WILL PERSIST THROUGH TOMORROW. WITH
PLENTY OF MOISTURE TRAPPED IN THE BOUNDARY LAYER AND FAIRLY LIGHT
WINDS ALOFT...A MIXED BAG OF MVFR AND IFR CEILINGS ARE EXPECTED TO
CONTINUE THROUGH THE OVERNIGHT HOURS INTO THURSDAY LATE MORNING.
CEILINGS MAY LIFT AND SCATTER FOR VFR MIDDAY THURSDAY THROUGH THE
AFTERNOON. HOWEVER...WEAK SURFACE GRADIENTS FAVOR SOME REDEVELOPMENT
OF STRATUS AND/OR FOG AGAIN THURSDAY EVENING DESPITE INCREASING HIGH
LEVEL MOISTURE AHEAD OF A STRONG STORM SYSTEM EXPECTED ON FRIDAY.

KSEA...MVFR CEILINGS WITH POSSIBLE TEMPO IFR CEILINGS AFTER 08Z. MAY
SEE SOME BRIEF IMPROVEMENT TO VFR 19Z-02Z...BUT MVFR EXPECTED TO
REDEVELOP AGAIN THURSDAY EVENING. LIGHT NORTHERLY SURFACE WINDS
EXPECTED THROUGH THURSDAY.

&&

.MARINE...ITS THE CALM BEFORE THE STORM OF SORTS THIS EVENING. ONLY
ISSUE OVERNIGHT AND THURSDAY IS HAZARDOUS SEA CONDITIONS CONTINUING
OVER THE COASTAL WATERS.

AS PREVIOUSLY ALLUDED TO...FRIDAY AND FRIDAY NIGHT REMAIN THE PERIOD
OF INTEREST...AND ONE WHICH COULD BE RATHER HAZARDOUS FOR MARINE
INTERESTS ACROSS ALL WATERS OF WESTERN WASHINGTON. 00Z MODEL RUNS
MAINTAIN THEIR OVERALL AGREEMENT IN DEVELOPING A RAPIDLY DEEPENING
SURFACE LOW AS IT APPROACHES THE NORTHERN WASHINGTON COAST ON FRIDAY
AFTERNOON.

THE POTENTIAL THREATS FROM THIS STORM ARE SEVERAL FOLD. IT SEEMS
LIKELY THAT GALE FORCE WINDS WILL DEVELOP ACROSS ALL OR MOST OF THE
WATERS BY FRIDAY AFTERNOON. STORM FORCE WINDS REMAIN A DISTINCT
POSSIBILITY OVER THE COASTAL WATERS...AND PERHAPS THE WEST ENTRANCE
TO THE STRAIT AS WELL. WITH THE SURFACE LOW EXPECTED TO TREK ACROSS
THE OLYMPIC PENINSULA...THIS SUGGESTS VERY STRONG SOUTHEAST WINDS
VEERING NORTHWESTERLY OVER COASTAL WATERS...THE STRAIT...AND
NORTHERN INLAND WATERS.

FOR THE COASTAL AREAS...THE RAPIDLY DEEPENING SURFACE LOW ARRIVING
NEAR HIGH TIDE PRESENTS A THREAT OF COASTAL FLOODING MIDDAY FRIDAY.
VERY LARGE SURF GENERATED THIS STORM...STRONG NORTHWEST WIND...AND A
SECONDARY HIGH TIDE LATE FRIDAY NIGHT BRINGS ANOTHER CHANCE AT
COASTAL FLOODING. FOR THE NORTHERN INLAND WATERS...A SIMILAR
COINCIDENCE OF HIGH TIDE AND LOW PRESSURE WILL CREATE A POSSIBILITY
OF COASTAL FLOODING FRIDAY AFTERNOON. A STRONG NORTHWESTERLY SURGE
DOWN THE STRAIT OF GEORGIA COMBINED WITH HIGH TIDE EARLY SATURDAY
MORNING PRESENTS A SECONDARY POSSIBILITY OF COASTAL FLOODING. TIMING
IS CRUCIAL TO ANY OF THE ABOVE OCCURING AND ANY FLOODING THAT
WOULD OCCUR WOULD LIKELY BE WITHIN AN HOUR OR TWO OF HIGH TIDE.

A COASTAL FLOOD WATCH COVERING THESE WILL LIKELY BE ISSUED EARLY
THURSDAY MORNING ALONG WITH THE MORNING MARINE FORECAST PACKAGE.

A STRONG SURFACE HIGH IS EXPECTED TO BUILD INTO INTERIOR BRITISH
COLUMBIA SATURDAY NIGHT AND SUNDAY. THIS WILL CREATE STRONG FRASER
VALLEY OUTFLOW WIND...PERHAPS GALE FORCE AT TIMES. 27

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...WINTER STORM WATCH FOR THE OLYMPICS AND THE CENTRAL AND
        NORTH CASCADES.
     HIGH WIND WATCH FOR THE CENTRAL AND NORTH COAST...STRAIT OF
        JUAN DE FUCA AREA...SAN JUAN ISLANDS AND WESTERN WHATCOM
        COUNTY.
PZ...SMALL CRAFT ADVISORY FOR ROUGH BAR CONDITIONS AT THE GRAYS
        HARBOR ENTRANCE.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS ON THE COAST AND AT
        THE WEST ENTRANCE.
     STORM WATCH FOR THE CENTRAL AND NORTH WASHINGTON COAST FOR
        FRIDAY.
     GALE WATCH FOR THE STRAIT AND ALL INLAND WATERS FOR FRIDAY.

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