Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000
FXUS66 KSEW 300454
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
855 PM PST THU JAN 29 2015

.SYNOPSIS...AN UPPER RIDGE WILL PROVIDE DRY AND MILD WEATHER THROUGH
SATURDAY. A FRONT WILL BRING RAIN BACK TO THE AREA SUNDAY AND EARLY
NEXT WEEK.

&&

.SHORT TERM...AN UPPER RIDGE WILL BE OVER THE AREA THROUGH SATURDAY
NIGHT WITH LOW LEVEL OFFSHORE FLOW...KEEPING THE WEATHER DRY WITH
SOME NIGHT AND MORNING FOG EACH DAY. HIGH CLOUDS WILL BEGIN TO
INCREASE OVER THE AREA FRIDAY NIGHT AS WEAK WEATHER SYSTEMS MOVE
OVER THE TOP OF THE RIDGE. HIGHS WILL BE ABOVE NORMAL THE NEXT
COUPLE OF DAYS...MAINLY IN THE 50S.

A FRONTAL SYSTEM WILL BRING A LITTLE RAIN TO THE AREA SUNDAY. MODELS
THE LAST FEW DAYS HAVE BEEN WAFFLING A BIT WITH THE STRENGTH AND
TIMING OF THIS SYSTEM BUT NOW SEEM TO BE COMING INTO BETTER
AGREEMENT SHOWING ALL AREAS GETTING A FEW TENTHS OF AN INCH OF RAIN
DURING THE DAY. SCHNEIDER

.LONG TERM...PREVIOUS DISCUSSION...ANOTHER PACIFIC FRONTAL SYSTEM
WILL BRING A ROUND OF WET WEATHER TO WESTERN WASHINGTON ON MONDAY.
SNOW LEVELS WILL BE LOWER...AROUND 4000 FEET...WITH A FEW INCHES OF
SNOW IN THE MOUNTAINS. MODELS TRY TO BRING A WEAK UPPER LEVEL RIDGE
TO THE REGION ON TUE FOR DRIER WEATHER. THE RIDGE MAY FLATTEN/WEAKEN
BY MIDWEEK AS MORE MOISTER ROLLS THROUGH THE PAC NW. 33

&&

.HYDROLOGY...FLOODING IS NOT EXPECTED FOR THE NEXT 7 DAYS.

&&

.AVIATION...A BROAD SOMEWHAT FLAT UPPER LEVEL RIDGE WILL REMAIN OVER
THE PACNW TONIGHT AND FRIDAY. A SURFACE HIGH CENTERED OVER E WA WILL
MAINTAIN WEAK LOW LEVEL OFFSHORE FLOW. THE AIR MASS REMAINS DRY AND
SATELLITE IMAGERY AND OBS SHOW CLEAR SKIES CONTINUING THIS EVENING.

GOOD RADIATIONAL COOLING CONDITIONS ARE EXPECTED TONIGHT. AREAS OF
FOG OR LOW STRATUS WILL FORM OVERNIGHT OVER S PUGET SOUND AND THE SW
INTERIOR FOR IFR CONDITIONS. SURFACE WINDS WILL BE WEAK OR CALM AND
04Z TEMP-DEW POINT DEPRESSIONS WERE MOSTLY 2F OR LESS. OVER CENTRAL
PUGET SOUND...A LITTLE BIT OF N PRESSURE GRADIENT HAS KEPT N WINDS
IN THE 3-8 KT RANGE THIS EVENING WITH T/TD DEPRESSIONS IN THE 3-6
DEGREE RANGE. THE N FLOW SHOULD WEAKEN OVERNIGHT...BUT IT MAY HOLD
OFF FOG FORMATION LONG ENOUGH TO LIMIT THE COVERAGE TO JUST PATCHY.
KPAE SHOULD GET IFR FOG AS N WINDS WILL CREATE A LOCAL UPSLOPE FOG
COMING OFF OF EVERETT HARBOR.

THE RIDGE AND DRY AIR MASS WILL KEEP SKIES MOSTLY CLEAR ON FRIDAY.
THE MORE PERSISTENT FOG/STRATUS OVER THE S PART SHOULD CLEAR BY
MIDDAY WITH PATCHY FOG ELSEWHERE CLEARING EARLIER.

KSEA...GOOD VFR CONDITIONS ARE EXPECTED TONIGHT AND FRIDAY. EARLY
MORNING IFR FOG/STRATUS IS THE ONLY ISSUE. WEAKENING N WINDS
OVERNIGHT SHOULD HOLD OFF THE FOG FORMATION LONG ENOUGH SO THAT IT
ONLY HAS A SMALL CHANCE OF DEVELOPING...SO I WILL LEAVE IT OUT OF
THE TAF FOR NOW. SURFACE WINDS WILL REMAIN N-NE 4-7 KT THROUGH 12Z
THEN WEAKEN TO 2-4 KT. KAM

&&

.MARINE...A SURFACE RIDGE CENTERED OVER EASTERN WASHINGTON WILL
MAINTAIN WEAK OFFSHORE FLOW THROUGH SATURDAY. PRESSURE GRADIENTS
ACROSS WESTERN WASHINGTON WILL REMAIN WEAK...PRODUCING N TO NE WINDS
ALONG THE COAST AND THROUGH PUGET SOUND...AND EASTERLY WINDS THROUGH
THE STRAIT.

MODELS HAVE BEEN CONSISTENT THE PAST FEW RUNS IN BRINGING A WEAK
FRONT ACROSS THE AREA SUNDAY. 00Z NAM AND GFS BOTH KEEP THE SURFACE
WINDS OVER THE COASTAL WATERS BELOW 20 KT. THE 12Z 4KM WRF-GFS WAS
JUST SLIGHTLY STRONGER WITH A SMALL AREA OF 20-21 KT WINDS ALONG THE
N COAST. STILL LOTS OF TIME FOR THE MODELS TO CHANGE WITH 5 MORE
MAIN MODELS RUNS TO ARRIVE BEFORE SUNDAY.

MODELS ARE STILL HAVING TROUBLE WITH THE TRAILING FRONT ON MONDAY.
12Z ECMWF STILL SHOWS A STRONGER LOW THAN THE OTHER MODELS...GFS IS
STILL WEAKEST WITH AN OPEN SURFACE TROUGH. EVEN IF THE ECMWF IS
CORRECT THIS SYSTEM WILL STILL FALL IN THE SCA RANGE. KAM

&&

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

&&

$$

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