Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 242302
AFDSEW

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

.SYNOPSIS...HIGH PRESSURE AT THE SURFACE AND ALOFT WILL BUILD OVER
WESTERN WASHINGTON TONIGHT. THE SURFACE HIGH WILL SHIFT EAST OF THE
CASCADES SUNDAY INTO MONDAY. FOG WILL LIKELY DEVELOP DURING THE
NIGHT AND MORNING HOURS AND TEMPERATURES WILL BE QUITE MILD FOR LATE
JANUARY. WEAK FRONTS WILL REACH THE AREA LATE MONDAY NIGHT THROUGH
ABOUT THURSDAY GIVING CLOUDS AND A CHANCE OF LIGHT RAIN AT TIMES.

&&

.SHORT TERM...THE WARM FRONT THAT PASSED THROUGH MUCH OF THE AREA
LAST NIGHT AND THIS MORNING HAS PUSHED NORTH OF THE CANADIAN BORDER
THIS AFTERNOON. WITH THE RATHER WARM AND MUGGY AIR MASS IN
PLACE...SOME LIGHT RAIN OR DRIZZLE REMAINS ALONG THE COAST AND IN
THE FAR NORTHERN INTERIOR. RAIN CHANCES THIS EVENING WILL BE LIMITED
TO NORTHERN PORTIONS OF THE AREA...THEN SKIES WILL GRADUALLY BECOME
PARTLY CLOUDY FROM THE SOUTH.

DEWPOINTS ACROSS THE AREA ARE WELL INTO THE 50S THIS AFTERNOON...SO
ANY RADIATIONAL COOLING WILL LIKELY GIVE AREAS OF FOG -PARTICULARLY
IN THE INTERIOR LOWLANDS. LOWS TONIGHT WILL STRUGGLE TO DROP BELOW
50 DEGREES.

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 16C-17C PER THE 18Z 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.

THE LATEST GFS AND CANADIAN SOLUTIONS ARE FASTER WITH A WEAK FRONT
AND ASSOCIATED SHORT WAVE TROUGH...NOW BRINGING IT INTO WESTERN
WASHINGTON MONDAY NIGHT INTO TUESDAY. HENCE RAIN CHANCES FOR THIS
PERIOD WERE INCREASED. EXPECT TEMPERATURES TO REMAIN 10 DEGREES OR
MORE ABOVE NORMAL FOR THIS TIME OF THE YEAR THROUGH TUESDAY. ALBRECHT

.LONG TERM...THE GFS AND CANADIAN SOLUTIONS SHOW A WEAK TROUGH
REMAINING OVER THE AREA ON WED THAT IS FOLLOWED BY ANOTHER WEAKENING
FRONT THU OR THU EVENING. THERE WILL LIKELY BE SOME PERIODS THAT
WILL BE DRY IN THE TUE NIGHT THROUGH THU NIGHT PERIOD...BUT MODEL
CONSISTENCY AND CONTINUITY WITH THESE VERY WEAK FEATURES IS NOT TOO
HIGH AT THIS TIME. AS A RESULT...FORECASTS WILL INDICATE CLOUDS AND
A CHANCE OF SHOWERS WITH LOWS IN THE 40S AND HIGHS IN THE LOWER TO
MID 50S.

THE EXTENDED MODELS CONTINUE TO SHOW RIDGING INCREASING ONCE AGAIN
OVER THE NORTHWEST THU NIGHT OR FRI AND CONTINUING THROUGH NEXT
WEEKEND. WITH THE RIDGE AXIS JUST OFFSHORE AND SURFACE HIGH OVER
SOUTHEASTERN BC...THE LOWER LEVEL AIR MASS...WHILE STILL MILD FOR
THIS TIME OF YEAR...WILL LIKELY NOT BE AS WARM AS THE ONE WE ARE
SEEING AT THIS TIME. ALBRECHT

&&

.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. THE SNOQUALMIE AT THE FALLS IS NOW RECEDING.
MINOR FLOODING REMAINS LIKELY ON THE SNOQUALMIE RIVER AT CARNATION
THIS EVENING...THOUGH IT APPEARS THAT THE RIVER WILL ONLY TOUCH THE
FLOOD STAGE AT THIS TIME.

HYDROLOGICALLY SIGNIFICANT RAIN HAS COME TO AN END AND DRY WEATHER
IS EXPECTED ACROSS THE AREA TONIGHT THROUGH MONDAY EVENING. THIS
WILL ALLOW RIVERS TO RECEDE NICELY. WEAK FRONTAL SYSTEMS LATE MONDAY
NIGHT INTO THU NIGHT ARE NOT EXPECTED TO PRODUCE HYDROLOGICALLY
SIGNIFICANT RAINFALL AMOUNTS. DRY WEATHER IS EXPECTED LATE NEXT WEEK
INTO NEXT WEEKEND. ADDITIONAL FLOODING IS NOT EXPECTED FOR THE
NEXT 7 DAYS. ALBRECHT

&&

.AVIATION...AN UPPER RIDGE WILL BUILD OVER THE AREA TONIGHT AND
SUNDAY WITH MODERATE WESTERLY FLOW ALOFT. AT THE SURFACE MODERATE
SOUTHERLY FLOW WILL EASE TONIGHT AND BE LIGHT OFFSHORE SUNDAY. THE
AIR MASS WILL REMAIN MOIST AND STABLE TONIGHT. CLOUDS WILL CLEAR
FROM THE SOUTH TONIGHT AND MONDAY BUT AREAS OF LATE NIGHT AND
MORNING FOG WILL FORM.

CEILINGS ARE GENERALLY IN THE 1000-2000 FOOT RANGE WITH LOCAL
CEILINGS BELOW 1000 FEET. THERE IS IMPROVEMENT IN SOUTHERN AREAS AS
A CLEARING TREND GETS UNDER WAY FROM SOUTH TO NORTH. SOME HOURS OF
VFR SEEM LIKELY THIS EVENING ESPECIALLY OVER SOUTHERN AREAS. AREAS
OF FOG/STRATUS WILL FORM OVERNIGHT ALONG THE I-5 CORRIDOR. ON SUNDAY
AFTERNOON CONDITIONS SHOULD IMPROVE TO VFR ALL AREAS.

KSEA...DISCUSSION ABOVE APPLIES. SOUTHERLY WIND 6-10 KT BECOMING
LIGHT OVERNIGHT. IFR FOG/STRATUS IS LIKELY FOR AT LEAST A FEW HOURS
10Z-15Z. CHB

&&

.MARINE...SURFACE HIGH PRESSURE WILL BUILD FROM THE SOUTH THIS
EVENING WITH THE LOW LEVEL FLOW BECOMING LIGHT OFFSHORE ON SUNDAY.
THE LIGHT OFFSHORE FLOW PATTERN WILL CONTINUE INTO MONDAY. SMALL
CRAFT ADVISORIES FOR WIND CONTINUE ALONG THE NORTH COAST TONIGHT
ALONG WITH ADVISORIES FOR HAZARDOUS SEAS ON THE SOUTH COAST.
HAZARDOUS SEAS MAY CONTINUE OVER THE OUTER WATERS THROUGH MONDAY.

A WEATHER SYSTEM WILL ARRIVE ON TUESDAY. THIS IS LIKELY TO BRING
SMALL CRAFT ADVISORY SOUTHERLY WINDS TO MOST AREAS AT TIMES FROM
MONDAY AFTERNOON THROUGH TUESDAY. SMALL CRAFT ADVISORY WESTERLY
WINDS ARE LIKELY IN THE STRAIT TUESDAY AFTERNOON. 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 WIND NORTHERN 4 COASTAL ZONES.
     SMALL CRAFT ADVISORY HAZARDOUS SEAS SOUTHERN 2 COASTAL
      ZONES.
     SMALL CRAFT ADVISORY FOR ROUGH BAR CONDITIONS GRAYS HARBOR
      BAR.

&&

$$

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