Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000
FXUS66 KSEW 231611
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
810 AM PST FRI JAN 23 2015

.SYNOPSIS...EXPECT RAIN AT TIMES ACROSS WESTERN WASHINGTON TODAY AND
TONIGHT AS A WARM FRONT MOVES ACROSS THE AREA. THE WARM FRONT
WILL SHIFT NORTH INTO BRITISH COLUMBIA ON SATURDAY WITH RAIN
TAPERING OFF. AN UPPER LEVEL RIDGE WILL GIVE DRY AND MILD WEATHER TO
THE AREA SUNDAY AND MONDAY. A WEAK COLD FRONT MAY BRING A FEW
SHOWERS ON TUESDAY.

&&

.SHORT TERM...SATELLITE IMAGERY AND OBSERVATIONS SHOW A WARM FRONT
SITTING FROM THE OREGON OFFSHORE WATERS NORTHWARD TO A TRIPLE POINT
NEAR HAIDA GWAII. THE WARM FRONT WILL GRADUALLY MOVE EAST AND
NORTHEAST ACROSS THE AREA THIS EVENING.

THE HEAVIEST PRECIPITATION ASSOCIATED WITH THE WARM FRONT APPEARS TO
BE AIMED INTO VANCOUVER ISLAND...ALTHOUGH AMSU RAIN RATE DATA FROM
EARLY THIS MORNING SHOW SOME AREAS OVER THE WASHINGTON OFFSHORE
WATERS GETTING UP TO 0.25 INCHES OF RAIN PER HOUR. THIS HEAVIER
PRECIPITATION WILL IMPACT THE SOUTHWESTERN/WESTERN OLYMPICS AND
NORTH CASCADES THIS AFTERNOON GIVING ABOUT 1-1.5 INCHES OF RAIN.
PRECIPITATION WILL GRADUALLY TAPER OFF...BUT NOT CLEANLY...AS THE
WARM FRONT MOVES NORTHEAST TOWARD BRITISH COLUMBIA BUT STRONG SW
FLOW ALOFT ONLY SLOWLY DECREASES. RIVERS FLOWING OFF THE OLYMPICS
AND NORTH CASCADES WILL RISE SHARPLY...BUT AT THIS TIME IT DOES NOT
APPEAR THAT RAINFALL AMOUNTS WILL BE SUFFICIENT TO CAUSE FLOODING ON
AREA RIVERS.

RIDGING WILL BUILD STRONGLY INTO THE PACIFIC NORTHWEST ON SATURDAY
AS 850 MB TEMPERATURES RISE TO NEAR 8C. DESPITE THE CLOUDS AND DRIPS
OF PRECIPITATION ON SATURDAY...TEMPERATURES WILL BE QUITE MILD
ACROSS THE AREA...RISING INTO THE MID AND UPPER 50S. LOW LEVEL
MOISTURE WILL DECREASE SATURDAY NIGHT LEAVING ONLY SOME HIGH CLOUDS
FOR SUNDAY. WITH LIGHT LOW LEVEL OFFSHORE FLOW ON
SUNDAY...TEMPERATURES WILL RISE TO AROUND 60 DEGREES...QUITE MILD
FOR LATE JANUARY. AFTER SOME AREAS OF MORNING FOG ON
MONDAY...ANOTHER MILD DAY WILL BE IN STORE WITH TEMPERATURES NEARING
THE 60 DEGREE MARK ONCE AGAIN.

CURRENT FORECASTS ARE IN GOOD SHAPE. NO CHANGES ARE EXPECTED THIS
MORNING. ALBRECHT

.LONG TERM...FROM THE PREVIOUS LONG TERM DISCUSSION...A WEAK COLD
FRONT MAY BRING A FEW SHOWERS TO WESTERN WA ON TUESDAY AS THE UPPER
LEVEL RIDGE EXITS EAST. ANOTHER WEAK DISTURBANCE MAY CLIP THE AREA
ON WED WITH ZONAL FLOW ALOFT. THE GFS IS A LITTLE FASTER THAN THE
ECMWF AT THIS POINT SO EXACT TIMING IS STILL UNCLEAR. BUT IT LOOKS
LIKE THE UPPER LEVEL RIDGE WILL REBUILD LATE IN THE PERIOD FOR
ANOTHER DRY SPELL. SO FOR NOW DRIER WEATHER IS IN STORE MAYBE THU OR
FRI INTO NEXT WEEKEND. 33

&&

.HYDROLOGY...THERE IS ONLY A LOW CHANCE OF MINOR FLOODING ON THE
SKOKOMISH RIVER NEAR POTLATCH AND THE NOOKSACK RIVER NEAR FERNDALE
TONIGHT INTO SATURDAY MORNING. BUT AT THIS TIME IT APPEARS THAT
RAINFALL AMOUNTS WILL BE INSUFFICIENT TO DRIVE ANY RIVERS ABOVE
FLOOD STAGE. OTHERWISE FLOODING IS NOT EXPECTED OVER THE NEXT 7
DAYS. ALBRECHT

&&

.AVIATION...WESTERLY FLOW ALOFT WILL CONTINUE TODAY AND TONIGHT. A
WARM FRONT WILL MOVE INTO THE AREA TODAY. THE FRONT WILL WEAKEN
TONIGHT THEN MOVE NORTH ON SATURDAY. AT THE SURFACE MODERATE
SOUTHEAST FLOW WILL WEAKEN SLOWLY TONIGHT AND SATURDAY. AIR MASS
MOIST AND STABLE.

MULTIPLE CLOUD LAYERS OVER WESTERN WASHINGTON TODAY AS THE WARM
FRONT MOVES INLAND. CEILINGS ARE VARIABLE WITH LOW IFR TO VFR
CEILINGS AT THE TERMINALS. THE TREND TODAY WILL BE TOWARD WORSE
CONDITIONS WITH CEILINGS LOWERING TO NEAR 2000 FEET MIDDAY AND TO
1000-2000 FEET LATER THIS AFTERNOON INTO THE EVENING. LOWER
CEILINGS...BELOW 1000 FEET...ARE LIKELY ALONG THE COAST AND STRAIT.
VISIBILITIES LOWERING TO 3-5SM WITH THE RAIN THROUGH TONIGHT.
IMPROVEMENT IS LIKELY ON SATURDAY.

KSEA...CEILINGS AROUND 4000 FEET LOWERING TO NEAR 2000 FEET BY
MIDDAY AND THEN TO 1000-2000 FEET LATER THIS AFTERNOON INTO THE
EVENING HOURS. VISIBILITY 3-5SM AT TIMES THIS AFTERNOON INTO THE
EARLY EVENING HOURS. WINDS SOUTHERLY 4 TO 8 KNOTS BECOMING 8 TO 12
KNOTS AFTER 00Z. CHB

&&

.MARINE...A WARM FRONT OVER THE OFFSHORE WATERS WILL MOVE INLAND
THIS MORNING. THE FRONT WILL WEAKEN OVER THE AREA TONIGHT THEN MOVE
NORTH ON SATURDAY. SURFACE HIGH PRESSURE WILL BUILD FROM THE SOUTH
SATURDAY AND SATURDAY NIGHT WITH THE LOW LEVEL FLOW BECOMING LIGHT
OFFSHORE ON SUNDAY. THE LIGHT OFFSHORE FLOW PATTERN WILL CONTINUE
INTO MONDAY. SMALL CRAFT ADVISORY WINDS WILL OCCUR AT TIMES OVER ALL
WATERS EXCEPT THE CENTRAL STRAIT THROUGH SATURDAY AFTERNOON. WINDS
WILL EASE ACROSS THE WATERS SATURDAY NIGHT WITH LIGHT WINDS SUNDAY.

KING TIDES...THE HIGHEST HIGH TIDES OF THE YEAR...ARE OCCURRING. THE
FORECAST HIGH TIDES FOR SEATTLE THIS MORNING AND SATURDAY MORNING
ARE 13.2 FEET. MINOR TIDAL OVERFLOW STARTS AT 13.5 FEET. SEA LEVEL
PRESSURE IS QUITE HIGH THIS MORNING...AROUND 1030 MB...WITH LIGHT
WINDS. THIS GAVE A SMALL NEGATIVE TIDAL ANOMALY DURING THE TIME OF
HIGH TIDE AT 710 AM THIS MORNING. SIMILAR METEOROLOGICAL CONDITIONS
ARE EXPECTED DURING THE SATURDAY MORNING HIGH TIDE AT 750 AM. THE
UPSHOT IS MINOR TIDAL OVERFLOW IS NOT EXPECTED. CHB

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY ALL WATERS EXCEPT THE CENTRAL STRAIT.
     SMALL CRAFT ADVISORY FOR ROUGH BAR CONDITIONS GRAYS HARBOR BAR.

&&

$$

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YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
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