Heavy Snow in Washington, March 9, 2009

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
330 AM PDT MON MAR 9 2009

.SYNOPSIS...FLURRIES SOUTH OF SEATTLE WILL END BY LATER THIS
MORNING. OTHERWISE...COLD AND DRY NORTHERLY FLOW OVER WESTERN
WASHINGTON TODAY. HIGH PRESSURE WILL BUILD OVER THE AREA TONIGHT
THROUGH FRIDAY WITH DRY WEATHER CONTINUING AND MODERATING
TEMPERATURES. A COLD FRONT AND UPPER LEVEL TROUGH WILL MOVE THROUGH
THE REGION FRIDAY NIGHT OR SATURDAY.

&&

.SHORT TERM...LATEST RADAR LOOP SHOWS A WEAK CONVERGENCE PRECIP BAND
OVER THE CENTRAL/SOUTH SOUND AND ANOTHER ONE FIZZLING OUT OVER THE
FAR NRN INLAND WATERS. NOT MUCH MORE THAN FLURRIES OR VERY LIGHT
SNOW OUT OF THIS AND NOTHING TO INDICATE ACCUMULATION OCCURING.
WILL KEEP A LOW POP MENTION FOR FLURRIES SOUTH OF SEATTLE THIS
MORNING AS MODELS DO SHOW SOME LIGHT QPF AND THE WEAK CONVERGENCE
WILL PROBABLY CONTINUE A FEW MORE HOURS. WITH DRY NLY FLOW
ALOFT...CLOUDS SHOULD GENERALLY CLEAR BY THIS AFTERNOON. WHILE IT IS
QUITE COLD ALOFT THE SUNSHINE SHOULD GIVE A STRONG BOOST TO TEMPS
THIS TIME OF YEAR. HAVE NUDGED TEMPS UP A FEW DEGREES TO THE UPPER
30S AND 40S.

HIGH PRESSURE WILL BUILD ALOFT TONIGHT WITH LIGHT OFFSHORE GRADIENTS
AND LITTLE OR NO CLOUDS. IT WILL BE QUITE CHILLY...WITH SOME SPOTS
POSSIBLY REACHING RECORD LOWS IN THE UPPER TEENS TO 20S. NOT
EXPECTING MUCH FOG WITH THE DRY OFFSHORE FLOW AND LOW DEW POINTS.
WEDNESDAY SHOULD BE A MOSTLY SUNNY DAY WITH HIGH TEMPS WARMING
ANOTHER FEW DEGREES. THE MODERATING TREND CONTINUES INTO THURSDAY AS
HIGH PRESSURE DOMINATES WESTERN WASHINGTON.

.LONG TERM...HIGH PRESSURE WILL BREAK DOWN ON FRIDAY AS A THE NEXT
TROUGH APPROACHES THE AREA. CLOUDS WILL INCREASE DURING THE DAY WITH
THE GFS BRINGING QPF TO THE N COAST DURING THE AFTERNOON. A FRONT
WILL MOVE THROUGH WESTERN WASHINGTON FRIDAY NIGHT...FOLLOWED BY A
COLD AND SHOWERY TROUGH ON SATURDAY. SHOULD BE A GOOD SNOW PRODUCER
FOR THE MOUNTAINS WITH SNOW LEVELS PLUMMETING TO MOST PASSES. MODELS
BRING A SERIES OF SYSTEMS ACROSS THE AREA SUNDAY INTO EARLY NEXT
WEEK WITH PERIODS OF RAIN AND MOUNTAIN RAIN OR SNOW.

&&

.AVIATION...WEAK SURFACE TROUGH OVER THE SOUTHERN PORTION OF THE
AREA COMBINED WITH A WEAK UPPER LEVEL TROUGH WILL KEEP SC DECK FROM
ABOUT KBFI SOUTHWARD THIS MORNING. CEILINGS WITH THE DECK BETWEEN
5000 AND 7000 FEET. A LIGHT FLURRY IS POSSIBLE EARLY THIS MORNING.
SURFACE TROUGH DISSIPATING THIS AFTERNOON WITH THE SC DECK GOING
WITH IT. AIR MASS DRYING OUT LATER TODAY INTO TONIGHT.

KSEA...CEILING NEAR 5000 FEET WITH CONDITIONS SCATTERING OUT LATER
THIS MORNING INTO THE AFTERNOON HOURS. WITH LIGHT SNOW SHOWERS
ENDING BY 06Z. NO ADDITIONAL ACCUMULATION. SC DECK LINGERING INTO
TUESDAY MORNING WITH SKIES CLEARING TUESDAY MORNING. NORTHEASTERLY
WINDS 6 TO 10 KNOTS. FELTON

&&

.MARINE...HIGH PRESSURE WILL CONTINUE TO BUILD OVER BRITISH COLUMBIA
WHILE A WEAK TROUGH OF LOW PRESSURE LINGERS OVER WESTERN WASHINGTON
THIS MORNING. THE RESULTING LOW LEVEL OFFSHORE FLOW WILL BE STRONG
ENOUGH FOR SMALL CRAFT ADVISORY WINDS OVER THE NORTHERN INLAND
WATERS AND AT THE WEST ENTRANCE TO THE STRAIT. THE TROUGH WILL
DISSIPATE LATER TODAY WITH THE OFFSHORE GRADIENTS STARTING TO
WEAKEN. BY LATE TONIGHT NO ADVISORIES ARE EXPECTED. THE HIGH WILL
WEAKEN AND SAG SOUTH WED AND THU WITH LIGHT OFFSHORE FLOW OVER THE
WATERS. THE HIGH WILL SHIFT EAST ON FRI WITH A COLD FRONT REACHING
THE AREA LATE FRI OR SAT. FELTON

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY COAST NORTHERN INLAND WATERS AND WEST
      ENTRANCE TO THE STRAIT.
     SMALL CRAFT ADVISORY GRAYS HARBOR BAR FOR ROUGH BAR CONDITIONS.

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