Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 211118
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
330 AM PST WED JAN 21 2015

.SYNOPSIS...AN UPPER LEVEL RIDGE WILL MOVE ACROSS WESTERN WASHINGTON
TODAY FOR ANOTHER DRY DAY WITH INCREASING HIGH CLOUDS THROUGH THE
DAY. A WARM FRONT WILL SPREAD RAIN INLAND ACROSS THE AREA MAINLY
LATE TONIGHT AND THURSDAY. ADDITIONAL FRONTS WILL MAINTAIN A
WET PATTERN THROUGH SATURDAY. AN UPPER LEVEL RIDGE WILL BRING MORE
SUNSHINE AND MILD WEATHER SUNDAY AND MONDAY.

&&

.SHORT TERM...AN UPPER LEVEL RIDGE WILL BRING DRY WEATHER TO WESTERN
WA TODAY. THE RIDGE AXIS IS RIGHT ALONG THE COAST THIS MORNING AND
WILL CROSS THE REGION THIS AFTERNOON. TEMPS DROPPED FAST OVERNIGHT
UNDER MOSTLY CLEAR SKIES. TEMPS ARE ONLY IN THE 20S TO 30S THIS
MORNING...WITH PATCHY FOG MAINLY IN THE SOUTH SOUND. CIRRUS CLOUDS
WILL INCREASE THIS AFTERNOON AS THE RIDGE MOVES INLAND WITH FILTERED
SUNSHINE EXPECTED. HIGHS WILL BE MILD AND IN THE 40S TO LOWER 50S.

A WEAK WARM FRONT WILL BRING LIGHT RAIN TO THE AREA LATE TONIGHT AND
THURSDAY. THIS FRONT WILL WEAKEN FURTHER THURSDAY AFTERNOON FOR JUST
A FEW LIGHT SPRINKLES.

ANOTHER WARM FRONT WILL CLIP WESTERN WA LATE THURSDAY NIGHT AND
FRIDAY FOR MORE RAIN...MAINLY ALONG THE COAST AND IN THE MOUNTAINS.
SNOW LEVELS WILL REMAIN HIGH WITH THIS SYSTEM...6000-7000 FT. THE
COLD FRONT WILL STALL OVER SOUTHERN B.C. FRI NIGHT THEN SLIDE S/SE
INTO WESTERN WA ON SAT. STRONG WESTERLY FLOW ALOFT WILL FOCUS HEAVY
PRECIP ALONG THE WEST SLOPES OF THE OLYMPICS AND CASCADES AND MODELS
SHOW 1-3 INCHES OF RAIN WITH THIS EVENT. SNOW LEVELS ARE STILL VERY
HIGH DURING THIS PERIOD. SHARP RISES ARE EXPECTED ON THE RIVERS
FLOWING OFF THE OLYMPICS AND NORTH CASCADES BUT FLOODING IS NOT
EXPECTED WITH THESE AMOUNTS. PRECIP WILL START TO TAPER OFF SAT
AFTERNOON AND EVENING AS AN UPPER LEVEL RIDGE REBUILDS OVER THE PAC
NW. 33

.LONG TERM...THE LATEST GFS AND ECMWF SOLUTIONS DEFLECT ALL MOISTURE
AWAY FROM WESTERN WA EARLY NEXT WEEK AS A STRONG UPPER LEVEL RIDGE
BUILDS OVER THE PAC NW. SO LOOK FOR DRIER WEATHER AHEAD...ALTHOUGH
WILL STILL SEE MORNING LOW CLOUDS AND FOG. A WEAK SYSTEM MAY BRING A
FEW LIGHT SHOWERS BY WED AS THE RIDGE SHIFTS INLAND. 33

&&

.HYDROLOGY...FLOODING IS UNLIKELY OVER THE NEXT SEVEN DAYS.

&&

.AVIATION...HIGH PRESSURE ALOFT WILL CONTINUE OVER THE PAC NW TODAY.
THE RIDGE WILL BEGIN TO WEAKEN TONIGHT. GENERALLY DRY
CONDITIONS...EXCEPT MOIST NEAR THE SURFACE. INCREASING HIGH LEVEL
MOISTURE LATE THIS AFTERNOON AND TONIGHT AS A FRONT APPROACHES.
STABLE CONDITIONS.

SATELLITE FOG PRODUCT AND OBS INDICATE PATCHY STRATUS WITH CIGS
BELOW 1K FT ACROSS THE SW INTERIOR/S PUGET SOUND...AND ALONG THE
STRAIT OF JUAN DE FUCA. FOG WILL ALSO BE PREVALENT ACROSS THE SW
INTERIOR AND S SOUND EXPANDING INTO THE CENTRAL SOUND WITH IFR
CIGS/VIS AT TIMES THROUGH 18Z. CLOUDS AND FOG SHOULD BURN OFF BY
AFTERNOON.

KSEA...NE WIND 3-6 KT...BECOMING NLY 5-9 KT AFTER 18Z. TEMP AND DEW
POINT SPREADS ARE CLOSE THIS MORNING SO FOG IS STILL POSSIBLE NEAR
OR AT THE TERMINAL. OCCASIONAL VISIBILITY AOB 1/2SM FG IS STILL
POSSIBLE...MAINLY 12Z-15Z. DTM

&&

.MARINE...HIGH PRESSURE BUILDING OVER THE INTERIOR WILL MAINTAIN
OFFSHORE FLOW TODAY. MARGINAL SMALL CRAFT ADVISORY EASTERLY WINDS
ARE EXPECTED AT THE WEST ENTRANCE STRAIT OF JUAN DE FUCA AND OVER
THE ADJACENT COASTAL WATERS BEFORE WINDS EASE THIS AFTERNOON.

A WEAK COLD FRONT WILL MOVE THROUGH THE WATERS TONIGHT AND THURSDAY.
SMALL CRAFT ADVISORY SOUTHERLY WINDS EXPECTED OVER THE COASTAL
WATERS. WIND OVER THE INTERIOR WILL LIKELY REMAIN BELOW 20
KT...EXCEPT THE E ENTRANCE WHICH COULD HAVE LOW-END SMALL CRAFT
WINDS.

ANOTHER SLIGHTLY STRONGER FRONT WILL REACH THE COASTAL WATERS
THURSDAY NIGHT WITH SMALL CRAFT WINDS SPREADING TO THE INTERIOR
WATERS N OF PUGET SOUND FRIDAY AND FRIDAY NIGHT.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT THROUGH WEDNESDAY
     MORNING FOR WEST ENTRANCE STRAIT OF JUAN DE FUCA AND COASTAL
     WATERS ZONE 150.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML




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