textproduct: Seattle/Tacoma

SYNOPSIS

Shower activity will lift northwards into Western Washington this afternoon. A shortwave on Friday will bring lowland rain and mountain snow. A change in the weather pattern this weekend through midweek with an upper level ridge favored to build over the Pacific Northwest, bringing drier conditions and patchy fog possible.

SHORT TERM /TODAY THROUGH SATURDAY/

Latest radar imagery shows weak radar echoes starting to push northwards into Western Washington. A quick burst of shower activity will push across the region this morning into the afternoon hours. A shortwave trough will quickly follow on Friday, bringing additional lowland rain and mountain snow. Snow levels Friday morning will be around 2500 ft near the passes and lower below 1000 ft by Friday evening. Around 6-12 inches of snow are expected at the passes, for which a Winter Weather Advisory has been issued for the north and central Cascades through late Friday evening. As for the lowlands, between 0.25-0.50 inches are expected, with higher amounts near the coast. Conditions will dry up on Saturday as an upper level ridge begins to build over the Pacific Northwest. High temperatures will in the 40s, and low temperatures will be in the 30s, with slightly cooler temperatures on Saturday. 29

LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/

There is good agreement between long term ensembles that the Pacific Northwest will be under the influence of an upper level ridge through midweek. In addition, lingering moisture from recent rainfall may promote fog development/low stratus across the region. 29

AVIATION

VFR for majority of terminals this morning, with localized areas of IFR/LIFR in low stratus and fog. Shower activity will return this morning and push northwards across the terminals this afternoon. This will bring widespread MVFR ceilings after 18Z. A second round of rain on Friday. Localized IFR/LIFR possible in the heavier bands of rain. N/NE winds at 5-12 kt will shift southerly late Thursday evening at 2-5 kt.

KSEA...VFR ceilings will lower this afternoon to MVFR as showers push through the terminal. MVFR ceilings will likely prevail through the TAF period. There is a slight chance (20-25%) of IFR ceilings between 09Z-16Z Friday as a second round of rain pushes through. N/NE winds this morning 10-15 kt will decrease to 5-7 kt. Winds will shift southerly this evening at 5-7 kt. 29

MARINE

A broad surface trough south of the area and high pressure over the interior of British Columbia will lead to northerly flow today. Weak surface trough moving over the waters tonight into Friday. High pressure will build over the area Friday night and remain through early next week.

Small craft advisory winds developing over the outer coastal waters tonight spreading to the inner coastal waters as well as the Western and Central portion of the Strait of Juan de Fuca Friday morning into Friday afternoon. Winds easing Friday night.

Seas building to 7 to 10 feet tonight and 10 to 14 feet Friday. Seas subsiding below 10 feet late Saturday afternoon into Saturday evening.

Light conditions due to the surface high pressure over the waters brings up the possibility of dense fog over the interior waters Saturday night through Tuesday. Felton

HYDROLOGY

No river flooding is expected over the next 7 days. The threat of landslides has greatly decreased across western Washington.

SEW WATCHES/WARNINGS/ADVISORIES

WA...Coastal Flood Advisory from 7 AM this morning to 1 PM PST this afternoon for City of Seattle-Lowlands of Pierce and Southern King Counties-San Juan County.

Winter Weather Advisory from 4 AM to 10 PM PST Friday for Cascades of Snohomish and Northern King Counties-Cascades of Southern King County-Cascades of Whatcom and Skagit Counties.

PZ...Small Craft Advisory from 1 PM Friday to 6 AM PST Saturday for Grays Harbor Bar.

Small Craft Advisory from 6 AM Friday to 1 AM PST Saturday for Central U.S. Waters Strait Of Juan De Fuca-West Entrance U.S. Waters Strait Of Juan De Fuca.

Small Craft Advisory from 1 PM Friday to 1 AM PST Saturday for East Entrance U.S. Waters Strait Of Juan De Fuca.

Small Craft Advisory from 1 AM Friday to 6 PM PST Saturday for Coastal Waters From Cape Flattery To James Island 10 To 60 Nm-Coastal Waters From Cape Flattery To James Island Out 10 Nm-Coastal Waters From James Island To Point Grenville 10 To 60 Nm-Coastal Waters From James Island To Point Grenville Out 10 Nm-Coastal Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm-Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm.