Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000
FXUS66 KSEW 281704
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
903 AM PST WED JAN 28 2015

.SYNOPSIS...CLOUDS WILL LINGER ACROSS WESTERN WASHINGTON THROUGH
TONIGHT WITH A CHANCE OF VERY LIGHT RAIN. AN UPPER RIDGE WILL
PROVIDE DRY AND MILD WEATHER THURSDAY THROUGH SATURDAY. A FRONT WILL
BRING RAIN BACK TO THE AREA SUNDAY AND EARLY NEXT WEEK.

&&

.SHORT TERM...THE LOW LEVEL AIR MASS REMAINS MOIST ACROSS WESTERN WA
WITH LINGERING LOW LEVEL CLOUDS ACROSS THE REGION. SKIES ARE PARTLY
TO MOSTLY CLOUDY. A WEAK UPPER LEVEL SHORT WAVE TROUGH WILL UNDERCUT
A RIDGE OVER THE PAC NW WHICH MAY RESULT IN ISOLATED LIGHT SHOWERS.
THE IR SHOWS THIS FEATURE OFF THE OREGON COAST THIS MORNING...SLOWLY
LIFTING N/NE. BUT OVERALL IT WILL BE MAINLY DRY ACROSS THE AREA. THE
HRRR AND NAM12 SHOW A FEW SPRINKLES WITH THIS SYSTEM AS IT MOVES
INLAND TONIGHT. BUT AGAIN RAINFALL AMOUNTS WILL BE LIGHT...TRACE OR
A COUPLE HUNDREDTHS IF ANYTHING.

AN UPPER LEVEL RIDGE WILL STRENGTHEN OVER THE AREA THU AND FRI FOR
MORE DRY AND STABLE WEATHER. EXPECT PATCHY LOW CLOUDS AND FOG DURING
THE MORNING HOURS...THEN PARTLY TO MOSTLY SUNNY SKIES IN THE
AFTERNOON. TEMPS WILL REMAIN ABOVE NORMAL WITH HIGHS IN THE LOW TO
MID 50S. 33

.LONG TERM...PREVIOUS DISCUSSION...MODELS REMAIN CONSISTENT IN
SHOWING THE AMPLIFIED RIDGE AXIS MOVING OVER THE PAC NW ON SATURDAY.
A LARGE SURFACE HIGH BUILDING E OF THE CASCADES WILL PROVIDE SOME
LIGHT OFFSHORE FLOW. THIS MAY HELP LIMIT FOG AND INHIBIT STRONG
INVERSIONS FROM DEVELOPING. SLY FLOW DURING THE AFTERNOON COULD
BRING SOME WARMER TEMPERATURES IF THERE IS ENOUGH MIXING. MOS
GUIDANCE TRENDS THE TEMPERATURES LOWER TOWARD CLIMATOLOGY. WILL
SPLIT THE DIFFERENCE AND STAY THE COURSE WITH HIGHS IN THE UPPER
50S.

THE RIDGE BREAKS DOWN SUNDAY NIGHT ALLOWING THE FIRST IN A SERIES OF
MOIST PACIFIC FRONTS TO MOVE INTO THE AREA. SUNDAY STILL LOOKS RAINY
AND THE LIKELY POPS SEEM APPROPRIATE. MODELS SHOW SOME WEAKER
TRAILING SYSTEMS INTO THE MIDDLE PART OF NEXT WEEK BUT NONE OF THESE
LOOK PARTICULARLY STRONG. TEMPERATURES WILL REMAIN NEAR OR SLIGHTLY
ABOVE AVERAGE.

&&

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

&&

.AVIATION...A WEAK UPPER LEVEL RIDGE WILL REMAIN OVER WESTERN
WASHINGTON TODAY AND TONIGHT. AT THE SURFACE WEAK OFFSHORE FLOW WILL
CONTINUE. THE LOWLANDS ARE COVERED WITH STRATUS THIS MORNING THOUGH
THE MOUNTAINS AND COAST ARE MOSTLY CLEAR. A WEAK IMPULSE MAY BRING
SOME CLOUDS AND SPOTTY LIGHT PRECIPITATION INTO SOUTHERN AREAS FROM
THE SOUTHWEST THIS AFTERNOON.

CEILINGS ARE GENERALLY 2-4K FT WITH A CLEARING TREND. HOWEVER THE
APPROACHING SHORTWAVE TROUGH WILL COMPLICATE MATTERS AS IT SPREADS A
DEEPER LAYER OF MOISTURE OVER THE SOUTH THIS AFTERNOON FROM THE
SOUTHWEST WITH CEILINGS BKN-OVC025-050.

KSEA...THE TERMINAL WILL BE IN AND OUT OF 2-4K FT CEILINGS THIS
MORNING WITH SOME CLEARING PERIODS. THE SHORT WAVE IN OREGON IS NOT
LIKELY TO MAKE IT TO KSEA TODAY SO MORE CLEARING IN THE AFTERNOON
SEEMS LIKELY. LIGHT NORTHERLY WIND. CHB

&&

.MARINE...A WEAK SURFACE RIDGE CENTERED OVER EASTERN WASHINGTON WILL
MAINTAIN WEAK OFFSHORE FLOW THROUGH SATURDAY. PRESSURE GRADIENTS
ACROSS WESTERN WASHINGTON WILL REMAIN WEAK WITH NORTHERLY AND
OFFSHORE WINDS OF LESS THAN 20 KT.

GFS AND ECMWF ARE IN GOOD AGREEMENT THAT A COLD FRONT WILL REACH THE
AREA LATER THIS WEEKEND. THE ECMWF BRINGS THE FRONT TO THE WA COAST
EARLY SUNDAY MORNING WHILE THE GFS HOLDS OFF UNTIL MIDDAY SUNDAY.
AT THIS POINT IT LOOKS LIKE THE FRONT WILL GENERATE SMALL CRAFT
ADVISORY LEVEL WINDS ON THE COAST AND OVER THE NORTH INTERIOR. CHB

&&

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

&&

$$

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