Small Craft Advisory 657, NWS Seattle, WA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
300 AM PST TUE MAR 1 2011

.SYNOPSIS...THE FIRST PART OF TODAY WILL BE A RELATIVE LULL IN
BETWEEN WEATHER SYSTEMS. A VIGOROUS FRONTAL SYSTEM WILL BRING RAIN
AND WIND FROM LATE THIS AFTERNOON INTO WEDNESDAY. THE WEATHER
PATTERN WILL STAY ACTIVE THURSDAY THROUGH SATURDAY AS ADDITIONAL
FRONTS MOVE THROUGH. SUNDAY AND MONDAY WILL SEE A BREAK IN THE
ACTIVE WEATHER AS THE STORM TRACK SHIFT SOUTH.

&&

.SHORT TERM...AFTER A BIT OF BREAK IN BETWEEN SYSTEMS THE FIRST HALF
OF TODAY...A STRONG WARM FRONT/COLD FRONT WILL MOVE THROUGH TONIGHT
AND WEDNESDAY...WITH RAIN AT TIMES SPREADING FROM SOUTH TO NORTH
ACROSS THE AREA LATER TODAY AND TONIGHT. POST FRONTAL SHOWERS WILL
PREVAIL BEHIND THE FRONT WEDNESDAY NIGHT AND THURSDAY. A SECOND
WEAKER FRONT IS FORECAST TO MOVE ONSHORE LATE THURSDAY OR THURSDAY
NIGHT. HIGHS WILL CONTINUE SEVERAL DEGREES BELOW NORMAL THE NEXT FEW
DAYS ALTHOUGH IT WILL BE BIT WARMER WEDNESDAY BEHIND THE WARM FRONT.

WIND...A DEEP SURFACE SURFACE LOW WILL TRACK SOUTH TO NORTH NEAR
130W TONIGHT AND WEDNESDAY MORNING. MODEL TRENDS HAVE BEEN TO SLOW
THE LOW DOWN A BIT. IT NOW LOOKS LIKE THE WINDIEST PERIOD FOR THE
COAST WILL BE WEDNESDAY MORNING...PERHAPS PEAKING MID TO LATE
MORNING HOURS. IT IS STILL A LITTLE TOO FAR OUT TO UPGRADE THE HIGH
WIND WATCH FOR THE COAST TO A WARNING. INSTEAD...WILL PUSH THE
BEGINNING TIME OF THE WATCH BACK ABOUT SIX HOURS. IT WILL NOW BE IN
EFFECT FROM MIDNIGHT TONIGHT THROUGH WEDNESDAY AFTERNOON. THE
INTERIOR WILL ALSO SEE SOME BREEZY TO WINDY CONDITIONS WEDNESDAY.

MOUNTAIN SNOW...MOIST AND UNSTABLE WEST FLOW ALOFT WILL BRING
CONTINUED SNOW SHOWERS TO THE MOUNTAINS TODAY. IT LOOKS MORE LIKE
ADVISORY AMOUNTS VERSUS HEAVY SNOW HOWEVER. WILL DOWNGRADE THE
WARNING TO AN ADVISORY FOR THE CENTRAL CASCADES. AS THE WARM FRONT
LIFTS NORTH LATE THIS AFTERNOON AND TONIGHT...FLOW ALOFT WILL BECOME
MORE SOUTHERLY. IN GENERAL...THIS SUPPORTS FURTHER ADVISORY
AMOUNTS BUT THE VOLCANOES COULD GET HEAVY SNOW IN THIS PATTERN. SNOW
LEVELS WILL BRIEFLY RISE TO 2000 TO 3000 FEET TONIGHT WITH THE WARM
FRONT THEN FALL AGAIN LATE WEDNESDAY BEHIND THE COLD FRONT.
ADDITIONAL MOUNTAIN SNOW WILL ACCOMPANY THE COLD FRONT ON WEDNESDAY.

LOWLAND SNOW...AIR ONCE AGAIN JUST COOL ENOUGH FOR SHOWERS TO BE IN
THE FORM OF SNOW AT TIMES OVER THE LOWLANDS THIS
MORNING...ESPECIALLY OVER THE HIGHER HILLS. WITH JUST HIT AND MISS
SHOWERS...EXPECT LITTLE IF ANY ACCUMULATION. THE LOW LEVELS WILL
WARM A BIT WITH THE WARM FRONT PRECLUDING ANY SNOW THREAT TONIGHT OR
WEDNESDAY MORNING. HOWEVER...THERE WILL BE YET ANOTHER MARGINAL
THREAT THURSDAY MORNING BEHIND THE COLD FRONT. HARD TO BELIEVE WE
ARE STILL WORRYING ABOUT SNOW WITH ONSHORE FLOW IN MARCH. SCHNEIDER

.LONG TERM...MODELS CONTINUE TO INDICATE ANOTHER FAIRLY VIGOROUS
FRONT WILL MOVE THROUGH FRIDAY NIGHT OR SATURDAY...FOLLOWED BY A
SPLIT FLOW PATTERN SUNDAY AND MONDAY. THOSE TWO DAYS LOOKING MORE
AND MORE LIKE A MOSTLY DRY AND PARTLY SUNNY PERIOD. SCHNEIDER

&&

.HYDROLOGY...HEAVY RAINFALL IS NOT ANTICIPATED ACROSS WESTERN
WASHINGTON OVER THE NEXT TEN DAYS. FLOODING IS NOT EXPECTED ON AREA
RIVERS...INCLUDING THE GREEN RIVER. SCHNEIDER

&&

.AVIATION...ANTICIPATE STRONG AND MOIST WLY FLOW ALOFT TO PERSIST
THRU TONIGHT. LOW LEVEL...OFFSHORE FLOW WILL GRADUALLY INCREASE
TODAY IN ADVANCE OF A WMFNT. PRECIP WILL ALSO GRADUALLY OVERSPREAD
THE AREA FROM THE S DURING THE DAY TODAY AHEAD OF THIS FRONT. THE
WMFNT WILL MOVE N ACROSS THE AREA OVERNIGHT...AND SHOULD BE DRAPED
ACROSS THE CENTRAL COAST /N OF OF GRAYS HARBOR/ EWD TO THE CASCADES
BY 0600 UTC.

CIGS WILL MAINLY BE IN THE MVFR CATEGORY TODAY...WITH THE MTNS
REMAINING OBSCURED. CIGS WILL PROBABLY LIFT INTO THE VFR CATEGORY
FOR A PERIOD BEHIND THE WMFNT TONIGHT. EXPECT THE HEAVIER SHOWERS
AT THE LOWER ELEVATIONS THIS MORNING TO MIX WITH SNOW OR BRIEFLY
CHANGE OVER TO WET SNOW. ACCUMULATIONS ARE STILL UNLIKELY BELOW 500
FT MSL.

KSEA...GENERALLY MVFR CIGS CAN BE EXPECTED TODAY. WINDS WILL BECOME
LIGHT NE THIS AFTERNOON.

&&

.MARINE...OFFSHORE FLOW WILL GRADUALLY INCREASE TODAY IN RESPONSE TO
A RAPIDLY INTENSIFYING LOW MOVING NE TOWARD THE OREGON OFFSHORE
WATERS. A WARM FRONT EXTENDING FROM THIS LOW WILL MOVE N ACROSS THE
AREA TONIGHT. EXPECT THE LOW TO DEEPEN TO NEAR 965 MB AS IT
APPROACHES HAIDA GWAII WED MORNING. THE COLD OR OCCLUDED FRONT
ASSOCIATED WITH THIS SYSTEM WILL SWEEP ACROSS THE AREA DURING THE
DAY WED.

ANTICIPATE GALE FORCE WINDS ACROSS MUCH OF THE AREA ON WED...WITH
STORM FORCE WINDS EXPECTED OVER THE COASTAL WATERS. SEAS WILL ALSO
BUILD RAPIDLY TO 20 TO 25 FT ON THE COASTAL WATERS WED MORNING.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...

WA...WINTER WEATHER ADVISORY CASCADES THROUGH WEDNESDAY MORNING.
    .HIGH WIND WATCH COAST LATE TONIGHT THROUGH WEDNESDAY.

PZ...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS COASTAL WATERS UNTIL
      NOON TODAY.
    .GALE WARNING COASTAL WATERS AND WEST ENTRANCE TONIGHT.
    .SMALL CRAFT ADVISORY CENTRAL AND EASTERN STRAIT TONIGHT.
    .STORM WATCH COASTAL WATERS AND WEST ENTRANCE WEDNESDAY.
    .GALE WATCH REMAINING WATERS...EXCEPT CENTRAL STRAIT WEDNESDAY.
    .SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR UNTIL NOON
TODAY.

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