Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000
FXUS66 KSEW 241658
AFDSEW

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

.SYNOPSIS...A WARM FRONT OVER NORTHERN PORTIONS OF 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 WEDNESDAY
NIGHT.

&&

.SHORT TERM...HEAVY RAIN FELL OVERNIGHT IN THE SOUTHWESTERN OLYMPICS
AND THE CENTRAL WASHINGTON CASCADES. THE RAINFALL AMOUNTS WERE
INSUFFICIENT TO CAUSE FLOODING ON THE OLYMPIC PENINSULA RIVERS...BUT
WAS ENOUGH TO CAUSE THE SNOQUALMIE RIVER AT THE FALLS AND THE
SNOQUALMIE RIVER AT CARNATION TO FLOOD. SEE THE HYDRO SECTION BELOW
FOR DETAILS.

RADAR AND OBSERVATIONS NOW SHOW THE PRECIPITATION ASSOCIATED WITH
THE PASSING WARM FRONT SITTING FROM JUST NORTH OF EVERETT INTO
VANCOUVER ISLAND AND NORTHWARD. THE WARM FRONT WILL LIFT NORTHWARD
INTO BRITISH COLUMBIA ABOUT MIDDAY. WHILE THE MAIN FRONTAL FORCING
WILL MOVE NORTH OUT OF THE AREA BY EARLY THIS AFTERNOON...LOW LEVEL
MOISTURE WILL BE SLOW TO SCOUR OUT THROUGH THIS EVENING. KLGX RADAR
CONTINUES TO SHOW LIGHT PRECIPITATION OFFSHORE MOVING TOWARD THE
COAST...AND SOME OF THIS WILL MAKE IT INLAND IN THE FORM OF LOW
CLOUDS AND SPRINKLES OR DRIZZLE TODAY. DESPITE THE LOW LEVEL
MOISTURE...TEMPERATURES ARE QUITE MILD WITH THE 8 AM TEMPERATURES IN
THE LOWER TO MID 50S ACROSS WESTERN WASHINGTON. THE RECORD HIGH OF
58 TODAY AT SEATAC AIRPORT WILL BE THREATENED DESPITE THE CLOUDS AND
DRIPS.

WITH ALL THE LOW LEVEL MOISTURE IN PLACE...ANY CLEARING AT ALL WILL
ALLOW AREAS OF FOG TO FORM IN THE INTERIOR VALLEYS OVERNIGHT
TONIGHT. LOWS WILL STRUGGLE TO GET DOWN TO 50 DEGREES
TONIGHT...QUITE WARM FOR LATE JANUARY.

LOW LEVEL MOISTURE IS EXPECTED TO FINALLY SCOUR OUT MIDDAY SUNDAY
LEAVING JUST SOME SCATTERED TO BROKEN HIGH CLOUDS. SUBSIDENCE WILL
RAISE TEMPERATURES AT 2000 FT TO 17C-18C PER THE 12Z NAM12 LATE SUN
AFTERNOON...AND IT SHOULD REACH 60 DEGREES IN MANY PLACES SUNDAY
AFTERNOON-BREAKING DAILY TEMPERATURE RECORDS FOR JAN 25. WITH LESS
CLOUD COVER SUNDAY NIGHT...EXPECT RADIATIONAL COOLING TO GIVE MORE
FOG SUNDAY NIGHT INTO MONDAY MORNING. THE TEMPERATURE ON MONDAY -IF
THE FOG LIFTS EARLY ENOUGH- WILL REACH 60 AGAIN...BREAKING THE
RECORD. BUT TEMPERATURE FORECASTING THIS TIME OF YEAR WHEN
INVERSIONS DOMINATE IS TRICKY. ALBRECHT

.LONG TERM...FROM THE PREVIOUS LONG TERM DISCUSSION...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...LOCALIZED RAINFALL AMOUNTS UP TO 2.5 INCHES FELL
OVERNIGHT IN THE CASCADE RIVER BASINS OF KING AND SOUTH SNOHOMISH
COUNTIES. THIS WAS ENOUGH TO PRODUCE FLOODING ON THE SNOQUALMIE
RIVER AT THE FALLS. MINOR FLOODING IS LIKELY ON THE SNOQUALMIE RIVER
AT CARNATION THIS AFTERNOON AND THIS EVENING. SEE THE LATEST FLOOD
WARNING STATEMENT FOR DETAILS. LOCALLY HEAVY RAIN ALSO FELL
OVERNIGHT IN THE CASCADES OF WESTERN WHATCOM COUNTY. THE NOOKSACK
RIVER AT FERNDALE WILL CONTINUE TO RISE TODAY...BUT AT THIS TIME IT
APPEARS THAT IT WILL REMAIN ABOUT A FOOT BELOW FLOOD STAGE.

DRY WEATHER IS EXPECTED ACROSS THE AREA LATER TODAY THROUGH ABOUT
WEDNESDAY. THIS WILL ALLOW RIVERS TO RECEDE NICELY. WEAK FRONTAL
SYSTEMS TUESDAY NIGHT INTO WEDNESDAY NIGHT ARE NOT EXPECTED TO
PRODUCE HYDROLOGICALLY SIGNIFICANT RAINFALL AMOUNTS. DRY WEATHER IS
EXPECTED LATE NEXT WEEK INTO NEXT WEEKEND AND ADDITIONAL FLOODING IS
NOT EXPECTED FOR THE NEXT 7 DAYS. ALBRECHT

&&

.AVIATION...WESTERLY FLOW ALOFT WILL CONTINUE TODAY. A WEAK WARM
FRONT OVER THE NORTH WILL MOVE NORTH THIS AFTERNOON. AN UPPER RIDGE
WILL BUILD OVER THE AREA TONIGHT AND SUNDAY. THE AIR MASS WILL
REMAIN MOIST AND STABLE.

CEILINGS ARE GENERALLY IN THE 1000-2000 FOOT RANGE WITH LOCAL
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...DISCUSSION ABOVE APPLIES. SOUTHERLY WIND 6-10 KT. CHB

&&

.MARINE...A WARM FRONT OVER THE NORTHERN INLAND WATERS WILL MOVE
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 TIDE FOR SEATTLE THIS MORNING IS 13.2 FEET AROUND 8
AM. MINOR TIDAL OVERFLOW STARTS AT 13.5 FEET. SEA LEVEL PRESSURE
REMAINS QUITE HIGH...ABOVE 1025 MB. CURRENTLY THE TIDAL ANOMALY
NEGATIVE 0.6 FEET GIVING AN ACTUAL HIGH TIDE ABOUT 12.6 FT. IN OTHER
WORDS THERE WILL BE NO MINOR TIDAL OVERFLOW. BURKE

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...FLOOD WARNINGS ARE IN EFFECT FOR PORTIONS OF THE SNOQUALMIE
      RIVER IN KING AND SNOHOMISH COUNTIES.
PZ...SMALL CRAFT ADVISORY COAST AND WEST ENTRANCE TO THE STRAIT FOR
      HAZARDOUS SEAS.
     SMALL CRAFT ADVISORY FOR ROUGH BAR CONDITIONS GRAYS HARBOR BAR.

&&

$$

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