Gale Watch 39, NWS Seattle, WA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
916 AM PDT TUE NOV 1 2011

.SYNOPSIS...AN UPPER LEVEL RIDGE WILL KEEP SKIES MOSTLY CLEAR TODAY
THROUGH EARLY WEDNESDAY...EXCEPT FOR PATCHY MORNING FOG AND LOW
CLOUDS OVER THE INTERIOR AND THIN HIGH CLOUDS ABOVE. CLEAR SKIES
TONIGHT WILL BRING ANOTHER ROUND OF EARLY MORNING TEMPERATURES IN
THE UPPER 20S AND 30S. A COLD FRONT WILL BRING RAIN AND MOUNTAIN
SNOW WEDNESDAY AFTERNOON AND NIGHT...FOLLOWED BY SCATTERED SHOWERS
THURSDAY WHEN A LARGE UPPER LEVEL TROUGH ARRIVES. A WEAK UPPER LEVEL
RIDGE WILL CROSS THE AREA FRIDAY...FOLLOWED BY ANOTHER FRONTAL
SYSTEM OVER THE WEEKEND.

&&

.SHORT TERM...EARLY MORNING FOG PRODUCT IMAGERY AND OBS SHOW A MIX
OF PATCHY FOG...STRATUS...AND CLEAR SKIES OVER MAINLY THE INTERIOR
THIS MORNING. WITH THE UPPER LEVEL RIDGE OVER THE AREA TODAY AS WELL
AS A SURFACE HIGH SKIES ARE EXPECTED TO CLEAR OUT BY MIDDAY.

ALTHOUGH THE UPPER LEVEL RIDGE AND SURFACE HIGH WILL SHIFT EAST
TONIGHT...THE RESIDUAL DRY AIR MASS AND MOSTLY CLEAR SKIES/OR JUST
THIN CIRRUS WILL LEAD TO ANOTHER ROUND OF LOW TEMPERATURES IN THE
UPPER 20S AND 30S EARLY WEDNESDAY MORNING. ISOLATED FREEZING FOG IS
STILL POSSIBLE SO SPOTTY ICE MAY FORM ON LOCAL ROADWAYS IN THE
COOLEST SPOTS. GFS SHOWS A LOT OF CIRRUS MOVING OVER THE AREA
TONIGHT AHEAD OF WEDNESDAYS COLD FRONT...THEN A BREAK WEDNESDAY
MORNING BETWEEN THE CIRRUS AND THE COLD FRONT. NAM12 SEEMS TO HAVE
THIS TREND AS WELL SO THERE COULD BE A SOME SUNSHINE AROUND
WEDNESDAY BEFORE THE FRONTAL CLOUDS ARRIVE. CURRENT FORECASTS SEEM
TO HANDLE THIS FAIRLY WELL.

MODELS REMAIN CONSISTENT WITH THE TIMING OF WEDNESDAYS COLD FRONT.
RAIN IS EXPECTED TO JUST REACH THE N COAST AROUND MIDDAY
WEDNESDAY...THEN MOVE INLAND DURING THE AFTERNOON...PROBABLY BARELY
REACHING PUGET SOUND BY 5 PM...THEN CROSS THE PUGET SOUND/I-5
CORRIDOR EARLY WEDNESDAY EVENING. GFS TAKES THE FRONT EAST OF THE
CASCADE CREST BY MIDNIGHT.

THE AIR MASS WITH THE FRONT IS COLD ENOUGH TO BRING A FEW INCHES OF
SNOW DOWN TO STEVENS PASS AND POSSIBLY SNOQUALMIE PASS AS WELL.
HIGHEST AMOUNTS LOOK LIKE THEY WILL BE OVER THE NORTH CASCADES WHERE
MOUNT BAKER MIGHT RECEIVE AROUND 0.80 INCHES OF LIQUID PRECIP
THROUGH WEDNESDAY NIGHT. WITH SNOW LEVELS STARTING OUT HIGH AND MOST
OF THE PRECIP FALLING EARLY IN THE EVENT...IT IS NOT CERTAIN HOW
MUCH OF THE PRECIP TOTAL WILL END UP FALLING AS SNOW. IT SEEMS THAT
WE ARE STILL USING LOWER FIRST STORM OF THE SEASON WARNING CRITERIA
FOR HEAVY SNOW IN THE MOUNTAINS...THAT IS 4 INCHES IN 12 HOURS OR 6
INCHES IN 24 HOURS. SO IT WOULD NOT BE A COMPLETE SURPRISE IF MT
BAKER OR PARADISE AT MT RAINIER PICKED UP THE RELATIVE SMALL AMOUNT
NEEDED FOR A FIRST STORM OF THE SEASON WARNING.

A LARGE UPPER LEVEL TROUGH WILL MOVE INLAND BEHIND THE FRONT...AND
OVER THE WEST COAST ON THURSDAY. TEMPERATURES WILL BE COLDEST WITH
THIS TROUGH WITH SNOW LEVELS DROPPING TO 2500 FEET OR SO. THE AIR
MASS WILL BE UNSTABLE BUT WINDS ALOFT WEAK...SO OROGRAPHIC EFFECTS
OVER THE MOUNTAINS WILL NOT CONTRIBUTE SUBSTANTIALLY TO SNOW
AMOUNTS. THE AREA WILL SEE SCATTERED SHOWERS...WITH SCATTERED SNOW
SHOWERS OVER THE MOUNTAINS. KAM

.LONG TERM...PREVIOUS DISCUSSION FROM THE 3 AM AFD...ON FRIDAY THE
UPPER TROUGH WILL PROGRESS EAST OF THE CASCADES AND LEAVE WESTERN
WASHINGTON UNDER THE NORTHERLY FLOW AHEAD OF THE NEXT RIDGE
UPSTREAM. THE SEQUENCE OF EVENTS FRIDAY NIGHT THROUGH SATURDAY NIGHT
WILL BE SIMILAR TO WHAT WE EXPECT WEDNESDAY THROUGH THURSDAY. THE
UPPER RIDGE WILL MOVE INLAND FRIDAY NIGHT... ANOTHER FRONTAL SYSTEM
WILL MOVE THROUGH THE AREA SATURDAY... FOLLOWED BY ANOTHER COOL
UPPER TROUGH SATURDAY NIGHT. THE SEQUENCE WILL PROBABLY REPEAT AGAIN
EARLY NEXT WEEK.  MCDONNAL

&&

.HYDROLOGY...FLOODING IS UNLIKELY DURING THE NEXT 7 DAYS.

&&

.AVIATION...THE AIR MASS IS STABLE WITH LIGHT NORTHERLY FLOW ALOFT.
THERE REMAINS SOME SCT-BKN STRATUS OVER THE NW INTERIOR WITH CIGS
BETWEEN 2500 AND 3500 FT.  THE REMAINDER OF WESTERN WASHINGTON HAS
HAD SOME PATCHES OF FOG AND LOW STRATUS DEVELOP WHICH AT THIS POINT
IS ONLY AFFECTING THE KOLM TERMINAL BUT IT IS SCATTERED THROUGHOUT
THE PUGET SOUND.

THE FOG AND LOW CLOUDS WILL GRADUALLY BURN OFF BUT...WITH THE LIGHT
GRADIENTS AND TIME OF YEAR IT WILL BE SLOW.  THE FOG IS LIKELY TO
SPREAD OUT A BIT THROUGH 18Z AND AFFECT A FEW MORE LOCATIONS BEFORE
THAT HAPPENS.

ONCE THE MORNING FOG/STRATUS BURNS OFF...THE REGION WILL BE LEFT
UNDER CLEAR VFR CONDITIONS THROUGH MID DAY WEDNESDAY AS A RIDGE
BUILDS ALOFT AND A TRANSITION TO OFFSHORE LOW LEVEL FLOW TAKES
PLACE. THERE WILL BE SOME CIRRUS CLOUDS FROM TIME TO TIME.  EXPECT
LESS FOG WEDNESDAY MORNING DUE TO THE OFFSHORE FLOW AND CIRRUS.

KSEA...STRATUS AND FOG HAS DEVELOPED OVER LAKE WASHINGTON...PORTIONS
OF THE SOUND AND INTERIOR VALLEYS THIS MORNING.  IT IS VERY SHALLOW
BUT AS IT LIFTS AND BURNS OUT OF THE AREAS TO THE NORTH THIS COULD
DRIFT ACROSS THE TERMINAL FOR A SHORT PERIOD OF TIME LATE THIS
MORNING REDUCING VSBYS TO BELOW 3SM AND CIGS AOB BKN-OVC005.
CURRENT TAF DOES NOT CARRY THIS POTENTIAL AND WILL LEAVE AS IS FOR
NOW BUT MAINTAIN A WATCH AND UPDATE AS NEEDED IF THIS MOISTURE HEADS
TOWARD THE TERMINAL.  BEYOND THAT...VFR CONDITIONS WILL CONTINUE
THROUGH AT LEAST MID DAY WEDNESDAY WITH LIGHT NORTHERLY FLOW TODAY
BECOMING EASTERLY THIS EVENING.  CERNIGLIA

&&

.MARINE...HIGH PRESSURE OVER THE OFFSHORE WATERS WILL GRADUALLY
SHIFT EAST OF THE CASCADES THROUGH THIS EVENING.  WINDS ARE
GENERALLY LIGHT OVER ALL THE WATERS THIS MORNING.  A SMALL CRAFT
ADVISORY FOR HAZARDOUS SEAS CONTINUES ALONG THE COAST THROUGH THIS
EVENING AND FOR THE WEST ENTRANCE TO THE STRAIT THROUGH MID
AFTERNOON DUE TO A 12 FT WLY SWELL WHICH WILL SLOWLY SUBSIDE THROUGH
THIS EVENING.

SOUTHEAST WINDS WILL INCREASE EARLY WEDNESDAY AHEAD OF A FRONTAL
SYSTEM APPROACHING FROM THE WEST.  A GALE WATCH IS IN EFFECT FROM 5
AM WEDNESDAY THROUGH EARLY WEDNESDAY EVENING FOR THE COAST AND THE
WEST ENTRANCE TO THE STRAIT FOR ABOUT A 50 PERCENT PROBABILITY OF
GALE FORCE WINDS OCCURRING AHEAD OF THE FRONT.  THIS WILL BE FURTHER
EVALUATED TODAY AND EITHER UPGRADED TO A WARNING OR REPLACED WITH A
SMALL CRAFT ADVISORY THIS AFTERNOON.  WINDS ARE EXPECTED TO REMAIN
SMALL CRAFT ADVISORY CRITERIA IN THE INTERIOR WITH THE FRONT.  AFTER
A PERIOD OF MODERATE TO STRONG ONSHORE FLOW WEDNESDAY NIGHT...WINDS
WILL DIMINISH AS A WEAK LOW MOVES SOUTHEAST THROUGH THE COASTAL
WATERS THU.

ANOTHER FRONT WILL LIKELY BRING ANOTHER ROUND OF SMALL CRAFT
ADVISORY SOUTHERLIES ON SATURDAY TO MOST OF THE WATERS.  CERNIGLIA

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS COAST THROUGH THIS
      EVENING..
    .SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS WEST ENTRANCE OF THE
      STRAIT THROUGH MID AFTERNOON.
    .SMALL CRAFT ADVISORY FOR ROUGH BAR CONDITIONS THROUGH THIS
      EVENING.
    .GALE WATCH COASTAL WATERS AND WEST ENTRANCE OF THE STRAIT 12Z
      WEDNESDAY THROUGH EARLY WEDNESDAY EVENING.

YOU CAN SEE AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML.