Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000
FXUS66 KSEW 241128
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
300 AM PST SAT JAN 24 2015

.SYNOPSIS...A WARM FRONT OVER WESTERN WASHINGTON WILL SHIFT NORTH
INTO BRITISH COLUMBIA THIS AFTERNOON. HIGH PRESSURE WILL PROVIDE DRY
AND MILD WEATHER ON SUNDAY AND MONDAY. FOG WILL LIKELY DEVELOP
DURING THE NIGHT AND MORNING HOURS. WEAK FRONTS WILL REACH THE AREA
LATER TUESDAY THROUGH THURSDAY.
&&

.SHORT TERM...A WARM FRONT IS DRAPED ACROSS THE SRN PORTION OF WRN
WA EARLY THIS MORNING. CURRENT RADAR SHOWS LIGHT RAIN ALONG THE
COAST EXTENDING INTO THE SW INTERIOR...PUGET SOUND AND THE CASCADES
AT 2 AM PST. WHILE THE LOWLANDS HAVE GENERALLY RECEIVED UNDER A
QUARTER INCH...THE COAST AND MOUNTAINS HAD 1 TO LOCALLY 2 INCHES THE
PAST 6 HOURS. THIS IS ENOUGH TO CAUSE SOME RIVERS TO RISE FURTHER
BUT FLOODING IS STILL NOT EXPECTED. SEE THE HYDRO DISCUSSION BELOW
FOR DETAILS.

THE RIDGE SHOULD BUILD TODAY LIFTING THE BAROCLINIC BOUNDARY NWD
ALONG WITH THE MOISTURE. RAIN SHOULD TAPER OFF OVER THE S COAST/SW
INTERIOR BY AFTERNOON AND BE MOSTLY CONFINED TO THE FAR N INTERIOR
BY LATE IN THE DAY. MODELS INDICATE RESIDUAL MOISTURE WILL HANG
AROUND SO IT SHOULD BE A CLOUDY YET MILD DAY TODAY. SNOW LEVELS WILL
BE QUITE HIGH ABOVE 8000 FEET. HIGH TEMPERATURES ACROSS THE GREATER
PUGET SOUND REGION WILL REACH THE UPPER 50S AND COULD COME CLOSE TO
OR SURPASS THE RECORD FOR THE DAY AT SOME LOCATIONS. THE RECORD FOR
SEA-TAC TODAY IS 58 SET IN 1995.

UPPER HEIGHTS WILL CONTINUE TO BUILD TONIGHT TO OVER 5750M AND THE
LOW LEVEL FLOW WILL BE LIGHT. MODELS SHOW WARMING ALOFT WHICH SHOULD
TRAP RESIDUAL MOISTURE WITHIN THE LOW LEVELS. AREAS OF FOG WILL
LIKELY DEVELOP LATE TONIGHT THROUGH SUNDAY MORNING AND COULD BE
STUBBORN TO MIX OUT ACROSS THE SW INTERIOR/FAR S PUGET SOUND SUNDAY
AFTERNOON. MOST SPOTS WILL SEE PARTIAL AFTERNOON SUNSHINE AND HIGHS
COULD REACH 60 IN SOME PLACES INCLUDING SEATTLE WHICH WOULD BE A
RECORD.

THE UPPER RIDGE WILL PERSIST OVER THE PAC NW INTO MONDAY. FOGGY
CONDITIONS SHOULD DEVELOP AGAIN IN THE MORNING AS INVERSIONS
STRENGTHEN. OFFSHORE FLOW DOES NOT APPEAR STRONG ENOUGH TO CLEAR OUT
MOISTURE SO FOG COULD AGAIN LINGER INTO THE AFTERNOON ACROSS PARTS
OF THE SW INTERIOR/S SOUND. OTHER AREAS WILL BE MOSTLY SUNNY BY
AFTERNOON WITH HIGHS IN THE UPPER 50S.

.LONG TERM...A WEAK FRONT WILL APPROACH ON TUESDAY. MODELS ARE
SLOWER WITH THE ARRIVAL OF RAIN WHICH IS NOT SURPRISING GIVEN THE
LARGE RIDGE THIS SYSTEM WILL BE ENCOUNTERING. POPS WERE TRIMMED BACK
WITH DRY WEATHER INDICATED FOR THE INTERIOR FROM ABOUT EVERETT SWD
FOR THE MORNING PERIOD. THE FRONT WILL STALL AND WEAKEN OVER THE
AREA TUESDAY NIGHT BUT MEASURABLE LIGHT RAIN IS LIKELY.

THE GFS LIFTS A SRN STREAM SHORT WAVE INTO THE AREA ON WEDNESDAY
WHICH IS FASTER THAN THE ECMWF. THERE IS LITTLE QPF SHOWN BY THE
CANADIAN SO THE WEDNESDAY FORECAST REMAINS UNCERTAIN. THURSDAY ALSO
LOOKS DRY ON MOST THE 00Z RUNS BUT ANOTHER SHORT WAVE WILL BE
PASSING JUST N OF OUR AREA. WILL KEEP A MENTION OF SHOWERS GOING FOR
NOW BUT THE TREND IS STARTING TO LOOK DRIER FOR THESE TWO DAYS. MOST
MODELS AGREE ON A STRONG RIDGE BUILDING BY FRIDAY AND SATURDAY. THIS
SHOULD PROVIDE DRY AND CONTINUED MILD WEATHER. MERCER

&&

.HYDROLOGY...RAINFALL AMOUNTS THE PAST 6 HOURS WERE GENERALLY AROUND
1 INCH IN THE MOUNTAINS. HOWEVER...THE CASCADES OF KING AND
SNOHOMISH COUNTIES HAVE SEEN UP TO 2 INCHES. THIS IS ON TOP OF THE
2-3 INCHES THAT FELL ON THURSDAY. THE ADDITIONAL RAINFALL IS CAUSING
SOME CONTINUED RISES ON A FEW RIVERS...MOSTLY IN THE SKOKOMISH AND
SNOQUALMIE RIVER BASINS. WHILE RIVERS WILL RUN HIGH TODAY...FLOODING
IS NOT ANTICIPATED. RAIN WILL TAPER OFF LATER TODAY WITH A PERIOD
OF MOSTLY DRY WEATHER SUNDAY AND MONDAY. WEAK SYSTEMS MOVING THROUGH
MID WEEK WILL NOT BRING HYDROLOGICALLY SIGNIFICANT RAINFALL.
FLOODING IS UNLIKELY OVER THE NEXT 7 DAYS.

&&

.AVIATION...WESTERLY FLOW ALOFT CONTINUING TODAY. WEAK WARM FRONT
OVER THE NORTHERN PORTION OF THE AREA LIFTING NORTH THIS AFTERNOON
AS AN UPPER RIDGE BUILDS. AIR MASS MOIST AND STABLE.

CEILINGS GENERALLY IN THE 1000-2000 FOOT RANGE WITH AREAS OF
CEILINGS BELOW 1000 FEET AND VISIBILITIES 3-5SM IN LIGHT RAIN OR
FOG. LITTLE IMPROVEMENT THROUGH THE EARLY AFTERNOON HOURS. SLOW
IMPROVEMENT LATER THIS AFTERNOON INTO THE EVENING HOURS.

KSEA...CEILINGS NEAR 500 FEET WITH VISIBILITIES 3-5SM AT TIMES IN
LIGHT RAIN OR FOG. SLOW IMPROVEMENT THIS AFTERNOON WITH CEILINGS
RISING INTO THE 1000-2000 FOOT RANGE BY LATE AFTERNOON/EARLY
EVENING. SOUTHERLY WIND 6 TO 10 KNOTS. FELTON

&&

.MARINE...A WARM FRONT OVER THE NORTHERN INLAND WATERS WILL LIFT
NORTH OF THE AREA THIS AFTERNOON. SURFACE HIGH PRESSURE WILL BUILD
FROM THE SOUTH THIS AFTERNOON AND EVENING WITH THE LOW LEVEL FLOW
BECOMING LIGHT OFFSHORE ON SUNDAY. THE LIGHT OFFSHORE FLOW PATTERN
WILL CONTINUE INTO MONDAY. A WEAK WEATHER SYSTEM WILL ARRIVE ON
TUESDAY.

WINDS HAVE EASED OVER MOST OF THE WATERS THIS MORNING. A SMALL CRAFT
ADVISORY IS IN EFFECT FOR THE COASTAL WATERS FOR HAZARDOUS SEAS. THE
SWELL WILL REMAIN ABOVE 10 FEET TODAY FOR THE INNER COASTAL WATERS
AND THE WEST ENTRANCE TO THE STRAIT AND THROUGH SUNDAY FOR THE OUTER
COASTAL WATERS.

KING TIDES...THE HIGHEST HIGH TIDES OF THE YEAR...ARE OCCURRING. THE
FORECAST HIGH TIDES FOR SEATTLE THIS MORNING IS 13.2 FEET. MINOR
TIDAL OVERFLOW STARTS AT 13.5 FEET. SEA LEVEL PRESSURE REMAINS QUITE
HIGH...ABOVE 1025 MB. CURRENTLY THE TIDAL ANOMALY IS JUST A TENTH OF
A FOOT ABOVE PREDICTED VALUES BUT WITH THE WINDS EASING IN ADDITION
TO THE HIGH SURFACE PRESSURE EXPECT THE ANOMALY TO TURN NEGATIVE
BEFORE HIGH TIDE THIS MORNING JUST BEFORE 8 AM. MINOR TIDAL OVERFLOW
IS NOT EXPECTED THIS MORNING. FELTON

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY COAST AND WEST ENTRANCE TO THE STRAIT FOR
     HAZARDOUS SEAS.
     SMALL CRAFT ADVISORY PUGET SOUND.
     SMALL CRAFT ADVISORY FOR ROUGH BAR CONDITIONS GRAYS HARBOR BAR.

&&

$$

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