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000
FXUS66 KSEW 111702
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 AM PST WED DEC 11 2013

.SYNOPSIS...AN UPPER LEVEL RIDGE WILL MOVE OVER WESTERN WASHINGTON
TODAY GIVING A DRY DAY WITH PARTLY SUNNY SKIES. A PACIFIC COLD FRONT
AND THE UPPER LEVEL TROUGH FOLLOWING IT WILL BRING RAIN THURSDAY AND
THURSDAY NIGHT WITH SNOW IN THE MOUNTAINS. A WEAKER FRONTAL SYSTEM
WILL REACH THE AREA THIS WEEKEND.

&&

.SHORT TERM...THE MORNING SATELLITE IMAGE SHOWS A PATCH OF FOG AND
STRATUS OVER THE SOUTHWEST...SOME HIGH CLOUDS COAST AND NORTH...AND
OTHERWISE PARTLY SUNNY SKIES OVER WESTERN WASHINGTON. HIGHS TODAY
WILL BE AROUND 40. A FLAT RIDGE OF HIGH PRESSURE WILL MOVE ACROSS
THE AREA TODAY AND THIS EVENING. CLOUDS WILL INCREASE TONIGHT AS A
PACIFIC WEATHER SYSTEM APPROACHES THE COAST.

RAIN SHOULD BEGIN ON THE COAST THURSDAY MORNING AND SPREAD INLAND
DURING THE AFTERNOON...A PATTERN THAT HAS BEEN CONSISTENT IN THE
MODELS FOR DAYS. HIGHS WILL RISE A FEW DEGREES INTO THE MID 40S.
SNOW WILL FALL IN THE MOUNTAINS...PROBABLY IN ADVISORY AMOUNTS.
THERE IS SOME POTENTIAL FOR FREEZING RAIN IN THE HIGHWAY PASSES.
WILL LOOK AT THIS FOR THE AFTERNOON FORECASTS.

RAIN WILL CHANGE TO SHOWERS LATE THURSDAY NIGHT AND TAPER FRIDAY.
HIGHS FRIDAY WILL BE IN THE MID 40S AGAIN. BURKE

.LONG TERM...PREVIOUS DISCUSSION...THE GFS/ECMWF BRING THE OFFSHORE
RIDGE AXIS TO THE COAST EARLY SATURDAY MORNING...WITH ANOTHER COLD
FRONT FOLLOWING BEHIND THE RIDGE. THIS SYSTEM STILL LOOKS WEAKER
THAN THE THURSDAY COLD FRONT. MODEL TIMING IS STILL SHOWING SOME
MINOR VARIABILITY... WITH THE LATEST MODEL SOLUTIONS BRINGING THE
COLD FRONT TO THE COAST SATURDAY NIGHT. PRECIP AMOUNTS DO NOT EVEN
APPEAR TO REACH ADVISORY LEVELS FOR THE CASCADES. MODERATE TO STRONG
W FLOW ALOFT IS EXPECTED BEHIND THE FRONT...WHICH SHOULD KEEP A
CHANCE OF SHOWERS GOING. GFS/ECMWF DIVERGE A LITTLE MORE FROM NEXT
TUESDAY ONWARD...SO CONFIDENCE KIND OF EVAPORATES. KAM

&&

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

&&

.AVIATION...AN UPPER LEVEL RIDGE IS OVER WESTERN WASHINGTON TODAY
WITH LIGHT OFFSHORE FLOW AT THE SURFACE. THE WINDS ALOFT ARE
WESTERLY. THERE IS PATCHY LOW CLOUDS AND FOG AROUND PUGET SOUND AND
SW INTERIOR THIS MORNING...WITH MAINLY SCT-BKN HIGH CLOUDS
ELSEWHERE. EXPECT VFR CONDITIONS THIS AFTERNOON AND EVENING WITH
INCREASING MID/HIGH LEVEL CLOUDS. THE UPPER LEVEL RIDGE WILL SHIFT
EAST TONIGHT WITH A COLD FRONT MOVING INLAND THURSDAY MORNING. 33

KSEA...EXPECT VFR CONDITIONS TODAY...WITH INCREASING MID/HIGH LEVEL
CLOUDS TONIGHT. SURFACE WINDS ARE LIGHT AND VARIABLE...BECOMING SLY
TONIGHT. 33

&&

.MARINE...EXPECT LIGHT OFFSHORE FLOW ACROSS WESTERN WA TODAY. WINDS
ARE LIGHT/VARIABLE ACROSS PUGET SOUND. OFFSHORE FLOW WILL INCREASE
TONIGHT THROUGH THU MORNING AS A COLD FRONT APPROACHES. WILL LIKELY
SEE SMALL CRAFT ADVISORY WINDS FOR THE COASTAL WATERS AND WEST
ENTRANCE OF JUAN DE FUCA. THIS FRONT WILL CROSS THE COASTAL WATERS
BY 18Z THU...THEN SHIFT INLAND THU AFTERNOON. LIGHT ONSHORE FLOW IS
FORECAST THU NIGHT AND FRIDAY. HIGH PRES WILL SHIFT INLAND FRI NIGHT
FOR GENERALLY LIGHT SURFACE WINDS. OFFSHORE FLOW WILL INCREASE ON
SAT AS OUR NEXT FRONTAL SYSTEM ARRIVES. 33

&&

.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