Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 041052
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
250 AM PST TUE MAR 3 2015

.SYNOPSIS...UPPER LEVEL RIDGING AND LOW LEVEL OFFSHORE FLOW WILL
MAINTAIN DRY AND GENERALLY MILD CONDITIONS THROUGH TONIGHT. A WEAK
SYSTEM WILL BRUSH THE AREA THURSDAY THROUGH EARLY FRIDAY MORNING
BRINGING CLOUDS AND A CHANCE OF A LITTLE RAIN TO THE NORTHERN THIRD
OF WESTERN WASHINGTON. REBOUNDING RIDGING ALOFT AND LOW LEVEL
OFFSHORE FLOW FRIDAY WILL RETURN FINE WEATHER TO THE AREA LATER
FRIDAY THROUGH THE WEEKEND.

&&

.SHORT TERM...A RIDGE OF HIGH PRESSURE IS CENTERED ALONG 135W EARLY
THIS MORNING. AT THE SURFACE...A RIDGE OF HIGH PRESSURE EXTENDS FROM
SOUTHEASTERN BRITISH COLUMBIA INTO MONTANA. THE END RESULT OVER
WESTERN WASHINGTON IS DRY AND COOL CONDITIONS. AFTER A CHILLY
MORNING WITH TEMPERATURES BELOW FREEZING OVER MUCH OF THE AREA...IT
WILL WARM INTO THE LOWER TO MID 50S THIS AFTERNOON. THAT WILL FEEL
WARM WITH THE BRIGHT SUN AND MINIMAL WIND.

A VERY WEAK SHORT WAVE TROUGH WILL MOVE OVER THE TOP OF THE UPPER
RIDGE INTO BRITISH COLUMBIA THURSDAY THROUGH VERY EARLY FRIDAY
MORNING. THE NAM12 AND GFS ARE TRENDING DRIER WITH EACH RUN...BUT
SHOW A SMALL CHANCE...20-30 PERCENT...OF SOME VERY LIGHT RAIN OVER
THE NORTHERN THIRD OF THE STATE...FROM ABOUT FORKS TO NORTH OF
EVERETT NORTHWARD TO THE CANADIAN BORDER...THURSDAY THROUGH EARLY
FRIDAY MORNING. THE ECMWF NOW KEEPS ALL CHANCES OF RAIN NORTH OF THE
BORDER. BUT EVEN THE DRY MODELS BRING RATHER THICK HIGH CLOUDS TO
THE NORTHERN HALF OF THE STATE. WILL MAINTAIN SMALL CHANCE POPS FOR
SPRINKLES OR A CHANCE OF 0.01 INCHES OF RAIN NORTH...BUT THE NEXT
FORECAST SHIFT MAY BE ABLE TO ELIMINATE THE POPS FROM THE FORECAST
IF MODELS CONTINUE TO TREND WEAKER WITH THE SHORT WAVE TROUGH
PASSING BY TO THE NORTH.

THE RIDGE WILL REBOUND OVER THE AREA ON FRIDAY. LIGHT WINDS WITH 500
MB HEIGHTS AROUND 570 DAM...850 MB TEMPERATURES AROUND 5C...AND LOTS
OF SUNSHINE WILL ALLOW TEMPERATURES FROM ABOUT SEATTLE OR SO
SOUTHWARD TO GET NEAR THE 60 DEGREE MARK FRIDAY AFTERNOON. ALBRECHT

.LONG TERM...AT THIS TIME THE WEEKEND LOOKS QUITE NICE. GLOBAL
MODELS KEEP RIDGING AND LIGHT WINDS OVER THE AREA WITH ONLY SOME
HIGH CLOUDS AT TIMES. DAYTIME HIGHS WILL BE NEAR THE 60 DEGREE MARK
AND LOWS WILL LIKELY STAY IN THE LOWER 40S MOST AREAS.

THE ENSEMBLE SPREAD INCREASES STARTING MONDAY AND THE ECMWF AND GFS
START TAKING DIFFERENT TRACKS. THE ECMWF SHIFTS THE RIDGE EAST ON
MONDAY KEEPING CONDITIONS DRY THEN BRINGS A SOUTHERN STREAM SYSTEM
TO THE OREGON OFFSHORE WATERS ON WEDNESDAY. THE GFS DIGS A NORTHERN
STREAM TROUGH INTO THE AREA FROM THE NORTHWEST MON THROUGH WED. BOTH
MODEL SOLUTIONS WOULD RESULT IN CLOUDIER AND WETTER CONDITIONS
ACROSS THE AREA STARTING MON OR TUE...BUT THE GFS WOULD RESULT IN
COOLER CONDITIONS AND A CHANCE OF SOME MUCH NEEDED SNOWFALL IN THE
MOUNTAINS. TIME WILL TELL WHICH SOLUTION WINS OUT. ALBRECHT

&&

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

&&

.AVIATION...NORTHERLY FLOW WILL PREVAIL OVER WESTERN WA TODAY. THE
AIR MASS IS DRY AND STABLE. VFR CONDITIONS ARE EXPECTED. 33

KSEA...LIGHT SE WINDS THIS MORNING BECOMING NLY TO 5 KT THIS
AFTERNOON. CLEAR SKIES AND VFR CONDITIONS. 33

&&

.MARINE...WINDS OVER THE WATERS WILL BE GENERALLY LIGHT THROUGH THE
END OF THIS WEEK WITH HIGH PRESSURE OVER THE AREA. WEAK ONSHORE FLOW
MAY DEVELOP BY SUNDAY. THE NEXT ORGANIZED SYSTEM MAY ARRIVE NEXT TUE
OR WED. 33


&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...NONE.

&&

$$

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