High Wind and Strong Wind in Washington, March 16, 2010

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
330 PM PDT TUE MAR 16 2010

.SYNOPSIS...EXPECT WINDY CONDITIONS THROUGH EARLY THIS EVENING AS A
FRONTAL SYSTEM MOVES THOUGH THE AREA. HIGH PRESSURE WILL BUILD
OFFSHORE WEDNESDAY THEN GRADUALLY SHIFT OVER WASHINGTON THURSDAY
THROUGH SATURDAY. ANOTHER FRONT AND COOL UPPER TROUGH WILL MOVE
ACROSS THE AREA LATER SUNDAY INTO EARLY NEXT WEEK.

&&

.SHORT TERM...A COLD FRONT ASSOCIATED WITH A MATURE 988 MB LOW IN
THE OFFSHORE WATERS IS MOVING THROUGH WESTERN WASHINGTON THIS
AFTERNOON. STRONG ISALLOBARIC RISES AT THE LEADING EDGE OF THE FRONT
IN CONJUNCTION WITH CHANNELING BY THE TERRAIN IS GIVING A BRIEF
PERIOD OF RATHER WINDY CONDITIONS LATE THIS AFTERNOON. A WIND
ADVISORY WAS ISSUED FOR THE PUGET SOUND AREA FROM JUST NORTH OF
EVERETT TO THE SOUTHERN END OF PUGET SOUND THROUGH 6 PM. WHILE THE
REMAINS OF A BACK BENT OCCLUSION WRAPPING AROUND THE OFFSHORE LOW
MOVES THROUGH THIS EVENING...EXPECT THAT WINDS WILL DIMINISH AS PRES
GRADIENTS START TO RELAX. SHOWERS WILL INCREASINGLY BECOME CONFINED
TO THE TERRAIN THIS EVENING AS STRONG SW FLOW ALOFT WITH THE BENT
BACK OCCLUSION INTERACTS WITH THE TERRAIN. SHOWERS WILL BUILD BACK
TOWARD THE LOWLANDS OF NORTHERN PUGET SOUND LATE TONIGHT AND EARLY
WEDNESDAY BEFORE DIMINISHING MIDDAY AS PRES GRADIENTS RELAX.
SNOWFALL AMOUNTS IN THE CASCADES ARE EXPECTED TO REMAIN BELOW 6
INCHES TONIGHT WITH HEAVIEST ACCUMULATIONS IN THE NORTH CASCADES
AROUND MOUNT BAKER.

BUILDING HIGH PRES ALOFT GIVES DRYING AND PARTLY SUNNY CONDITIONS
WED AFTERNOON. BUT WITH LOW LEVEL MOISTURE TRAPPED BENEATH A
LOWERING INVERSION IN NORTHERLY FLOW...AREAS OF LOW STRATUS AND SOME
PATCHY FOG WILL DEVELOP AROUND THE PUGET SOUND AREA AND LAST FOR A
FEW HOURS EARLY THU.

EXPECT DRY CONDITIONS THU THROUGH FRI WITH HIGH PRES. NORMALLY
COLDER LOCATIONS WILL SEE MORNING TEMPERATURES FALL WELL BELOW
FREEZING THU AND FRI...BUT TEMPERATURES WILL RECOVER WELL INTO THE
50S DURING THE DAY. ALBRECHT

.LONG TERM...A STRONG UPPER LEVEL RIDGE MOVES OVER THE AREA SAT THEN
SHIFTS EAST OF THE CASCADES SUN. BY THE WEEKEND EXPECT LIGHT
OFFSHORE FLOW...SUBSIDENCE...AND A WARMING MID MARCH SUN TO ALLOW
TEMPERATURES TO MODERATE TO ABOVE AVERAGE ONCE AGAIN WITH DAYTIME
TEMPERATURES INTO THE LOWER 60S MANY LOCATIONS. THE GFS AND ECMWF
ARE CONSISTENT IN BRINGING ANOTHER FRONT INTO THE AREA LATER SUN OR
SUN NIGHT FOR A CHANCE OF RAIN. THE FRONT IS FOLLOWED BY A PASSING
UPPER LEVEL TROUGH EARLY NEXT WEEK. MODELS ARE INCONSISTENT WITH THE
STRENGTH OF THE EARLY WEEK TROUGH WITH THE 12Z GFS SHOWING LOW
HEIGHTS AND LOTS OF SHOWERS. THE 12Z ECMWF SOLUTION IS MUCH WEAKER.
AT THIS TIME WILL MAINTAIN THE MOSTLY CLOUDY CONDITIONS WITH A
CHANCE OF SHOWERS MON ON. ALBRECHT.

&&

.HYDROLOGY...THE FLOOD RISK ACROSS WESTERN WASHINGTON AND THE GREEN
RIVER IS LOW THROUGH THE NEXT 10 DAYS.

A FRONTAL SYSTEM MOVING THROUGH WESTERN WASHINGTON TODAY WILL
PRODUCE GENERALLY LESS THAN 0.5 INCHES OF RAINFALL AS SNOW LEVELS
FALL FROM 3500 FEET LATER THIS EVENING TO 2500 FEET WED. A RIDGE OF
HIGH PRES WILL GIVE DRY CONDITIONS LATER WED THROUGH SAT NIGHT OR
SUN. ANOTHER TROUGH BRINGS SHOWERS LATER SUN OR SUN NIGHT...BUT
RAINFALL AMOUNTS ARE EXPECTED TO BE LIGHT. ALBRECHT

&&

.AVIATION...AN UPPER TROF WAS MOVING OVER WRN WA THIS AFTERNOON.
THIS SYSTEM WILL WEAKEN AS IT MOVES EWD OVERNIGHT. STRONG SW FLOW
ALOFT WILL DECREASE AND BECOME W. THE CDFNT HAS MOVED ACROSS THE
AREA...AND WINDS HAVE GENERALLY DROPPED OFF BEHIND IT.
HOWEVER...THIS WILL BE TEMPORARY AS WINDS WILL PICK UP AGAIN WITHIN
A COUPLE OF HOURS...AND THEN SUBSIDE LATER TONIGHT. MODERATELY
STRONG LOW LEVEL ONSHORE FLOW WILL WEAKEN OVERNIGHT. CIGS WILL
GENERALLY BE IN THE 3-5K FT RANGE TONIGHT.

KSEA...VFR CONDITIONS WILL PERSIST OVERNIGHT. ALTHOUGH WIND SPEEDS
HAVE DROPPED OFF BEHIND THE FRONT...EXPECT THEM TO PICK UP AGAIN IN
ABOUT TWO HOURS OR SO. THE GUSTY SW WINDS WILL THEN DIMINISH LATER
TONIGHT.

&&

.MARINE...A 988 MB LOW ABOUT 90 NM SW OF THE QUEEN CHARLOTTES WILL
CONTINUE MOVING NE. THE COLD FRONT ASSOCIATED WITH THIS SYSTEM WAS
MOVING ACROSS THE INLAND WATERS THIS AFTERNOON. WINDS HAVE OR WILL
EASE SOME ACROSS THE INLAND WATERS BUT WILL PICK UP AGAIN WITHIN
ABOUT TWO HOURS AS THE BENT BACK OCCLUSION...WHICH WAS PRESENTLY
OFFSHORE...PASSES TO THE N.

ONSHORE FLOW WILL PREVAIL OVER THE AREA TONIGHT AND WED IN THE
WAKE OF THE FRONT. THE FLOW WILL THEN BECOME NORTHERLY ON THU IN
RESPONSE TO A SURFACE HIGH BUILDING OVER BRITISH COLUMBIA. EXPECT
THE FLOW TO BECOME MORE OFFSHORE ON FRI.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...WIND ADVISORY CENTRAL PUGET SOUND REGION THROUGH 6 PM THIS
       EVENING.
PZ...A GALE WARNING IS IN EFFECT FOR THE COASTAL WATERS...WEST
       ENTRANCE TO THE STRAIT OF JUAN DE FUCA...AND THE PUGET
       SOUND/HOOD CANAL TIL 9 PM PDT TONIGHT.
    .A SMALL CRAFT ADVISORY FOR WINDS IS IN EFFECT FOR THE
       REMAINING WATERS.
    .A SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR
       CONDITIONS IS IN EFFECT UNTIL 6 PM PDT WED.

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