Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 261647
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
845 AM PST THU FEB 26 2015

.SYNOPSIS...A WEAK WEATHER SYSTEM WILL PRODUCE SCATTERED SHOWERS
ACROSS WESTERN WASHINGTON TODAY THROUGH FRIDAY...ESPECIALLY AT THE
COAST AND IN THE SOUTHWEST. A FEW INCHES OF SNOW WILL FALL IN THE
MOUNTAINS. AN UPPER RIDGE AND OFFSHORE FLOW WILL BRING SUNNY DAYS
AND COOL NIGHTS THIS WEEKEND. A WEAK SYSTEM WILL MOVE THROUGH SUNDAY
NIGHT AND MONDAY...WITH DRY WEATHER AGAIN TUESDAY AND WEDNESDAY.

&&

.SHORT TERM...THE PREDOMINANT WEATHER AROUND WESTERN WASHINGTON THIS
MORNING APPEARS TO BE FOG...OR AT LEAST MIST...WHICH APPEARS IN MANY
OBSERVATIONS. THERE IS ALSO SOME DRIZZLE. MODELS STILL SHOW SOME
ENHANCEMENT OF SHOWERS THIS AFTERNOON AS AN UPPER LEVEL LOW
APPROACHES FROM THE NORTHWEST. THERE APPEAR TO BE SEVERAL CLOUD
LAYERS UP TO 10K FEET. HIGHS TODAY WILL BE IN THE LOW 50S.

THE UPPER LEVEL LOW WILL MOVE SOUTH ALONG THE COAST TONIGHT AND INTO
OREGON FRIDAY. THERE WILL BE SHOWERS ASSOCIATED WITH THIS LOW...WITH
THE MOST SHOWERS ON THE COAST AND OVER THE SOUTHWEST. STARTING
FRIDAY NIGHT COLDER SURFACE AIR WILL MOVE SOUTH OUT OF BRITISH
COLUMBIA INTO WASHINGTON. THIS WILL CLEAR THE SHOWERS AND CLOUDS OUT
OF THE AREA FROM NORTH TO SOUTH. SATURDAY WILL BE CLEAR AND COOL.
HIGHS ON FRIDAY WILL BE IN THE LOW 50S AND WILL DIP TO AROUND 50 ON
SATURDAY. TEMPERATURES COULD FALL BELOW FREEZING SATURDAY NIGHT IN
WIND SHELTERED SPOTS. BURKE

.LONG TERM...PREVIOUS DISCUSSION...SUNDAY SHOULD BE ANOTHER DRY AND
SUNNY DAY...BUT THE UPPER FLOW WILL BACK TO NORTHWEST AS AN UPPER
SHORTWAVE STARTS DIGGING SOUTH ALONG THE COAST OF BRITISH COLUMBIA.
THAT SYSTEM WILL MOVE ACROSS THE FORECAST AREA SUNDAY NIGHT AND
MONDAY...PROBABLY BRINGING AREAS OF LIGHT PRECIPITATION TO WESTERN
WASHINGTON. THE SNOW LEVEL WILL BE AROUND 2000 TO 3000 FT. DRY
NORTHERLY FLOW WILL RESUME TUESDAY AND WEDNESDAY. OF COURSE THERE
ARE SOME DIFFERENCES IN THE LONGER RANGE MODELS...BUT THEY ALL
INDICATE THIS SAME BASIC PATTERN.   MCDONNAL

&&

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

&&

.AVIATION...AN UPPER TROUGH WILL DEVELOP OVER THE WEST COAST OF
NORTH AMERICA THROUGH FRIDAY. SURFACE LOW PRESSURE WILL SHIFT FROM
THE B.C. COASTAL WATERS TODAY TO THE WA COAST TONIGHT. THE LOW
PRESSURE AREA WILL CONTINUE SOUTH INTO THE GREAT BASIN BY THE
WEEKEND AS HIGH PRESSURE BUILDS OVER BRITISH COLUMBIA. MOIST AIR AND
SHOWERS THROUGH TONIGHT WILL GIVE WAY TO NORTHERLY FLOW AND CLEARING
BY FRIDAY NIGHT.

KSEA...SHOWERY CLOUDY WEATHER WILL CONTINUE THROUGH TONIGHT AND THEN
NORTHERLY WINDS AND CLEARING WILL DEVELOP STARTING AROUND FRIDAY
AFTERNOON.

&&

.MARINE...A WEAK FRONTAL SYSTEM WILL STALL AS IT MOVES ONTO THE
COAST THIS EVENING. THEN A DIFFUSE AND BROAD 1008 MB LOW WILL DROP
SSE FROM THE QUEEN CHARLOTTE SOUND INTO THE COASTAL WATERS TONIGHT.
PRESSURE GRADIENTS ARE EXPECTED TO REMAIN LIGHT OVER THE WATERS
THROUGH EARLY FRI. HIGH PRES WILL BUILD OVER THE INTERIOR OF BRITISH
COLUMBIA FRIDAY. AS THE LOW LATE TONIGHT PASSES SOUTH OF THE AREA
EXPECT N TO NE FLOW TO INCREASE. SMALL CRAFT ADVISORY CONDITIONS ARE
LIKELY OVER MOST OF THE WATERS LATER FRI OR FRI NIGHT INTO SAT. HIGH
PRES WILL MOVE INTO THE WATERS SUNDAY GIVING LIGHT WINDS. ANOTHER
LOW WILL DROP SOUTHEAST ACROSS THE AREA SUN NIGHT AND MONDAY...AGAIN
FOLLOWED BY NE WINDS AS HIGH PRESSURE BUILDS OVER B.C.

&&

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

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML





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