textproduct: Seattle/Tacoma

SYNOPSIS

A frontal system will continue to move across Western Washington through today with lowland rain, breezy winds, and mountain snowfall. Unsettled conditions continue on Wednesday. Drier, cool weather Thursday and Friday. A system will approach the area offshore over the weekend.

SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/

A frontal system continues to move across western Washington this afternoon. Steady rain through this evening with a brief convergence zone progressing across central Puget Sound tonight. South winds will remain breezy, peaking this afternoon and evening. A Wind Advisory remains in effect for the Grays Harbor County coast, as well as Admiralty Inlet and Everett region, with gusts of 35 to 45 MPH in these areas. Winds remain breezy elsewhere, with gusts ranging 25 to 40 MPH. Increasing foliage will make trees more susceptible to damage, which may result in localized power outages.

Snow levels around 4000 feet this afternoon will fall to 1500 feet by Wednesday morning, resulting in snow for the Cascades and Olympics, including the Passes. Snow will continue at times for the Cascades through Wednesday. Total snowfall amounts of 8 to 14 inches are expected for Snoqualmie and Stevens Passes, with locally higher amounts near 18" around White Pass and Mount Baker. A Winter Storm Warning remains in effect. Snow will subside Wednesday night.

An upper low will move across the Pacific Northwest on Wednesday. This will result in colder temperatures aloft, and increasing instability. Scattered showers will be around Wednesday, with the threat for isolated thunderstorms. The probabilities for thunderstorms peak between 15 to 25 percent, primarily during the afternoon. Lightning, breezy winds, as well as small hail may accompany any heavier showers.

Drier conditions will develop Wednesday night as conditions begin to clear for some areas. Temperatures by Thursday morning will fall into the low to mid 30s, resulting in potential frost concerns. Will also need to monitor freeze conditions for portions of south Sound. Otherwise, increasing sunshine is expected during the afternoon Thursday.

LONG TERM /FRIDAY THROUGH TUESDAY/

Weak upper ridging brings drier conditions on Friday. Will need to monitor the frost potential once again, mainly from Olympia southwards Friday AM. An upper low will track towards the west coast over the weekend. Uncertainty remains in ensembles in the location of the upper low by Sunday, which impacts the eastward extent of precipitation over the weekend. At this time, the highest probability for rain over the weekend is along the Olympic Peninsula, but precipitation chances extend through Puget Sound, especially by Sunday. The bulk of the energy then moves towards California by early next week, which may result in drier conditions for western Washington. However, slight chance of precipitation remains in the forecast at this time. A warming trend exists over the weekend with highs reaching the low to mid 60s. JD

AVIATION

A frontal system will continue to push across the region today, with most locations seeing MVFR to IFR cigs with 3-6 SM visibilities in light to moderate rainfall. The front will reach the coast around 00Z Wed, moving inland across the area after 06Z. Behind the frontal passage, conditions should improve to VFR. Scattered showers will move in behind the front, and a convergence zone is expected to develop behind the front late this evening into Wednesday. It will likely start north of the metro then slowly move southward during the day Wednesday. Outside of these areas, expecting mostly VFR conditions with a broken cloud deck for much of the day. In these showers and the convergence zone, there will be a 15-25% chance for some of these to be thunderstorms (highest probabilities Wednesday afternoon), but currently there is not high enough confidence to include this in any of the TAFs at this time.

Southwest winds 15-25 kt with gusts 25-35 kt will continue this afternoon as the front moves through. Winds will gradually taper overnight into Wednesday becoming south to southwest 5-10 kt through the overnight period. KPAE may temporarily change to N between around 03-12Z Tue.

KSEA...MVFR conditions continue with low ceilings and temporary reductions in visibility in light to moderate rain. Rain will cease this evening behind the frontal passage at around 03-05Z Tue. Clouds should lift and break apart for low-end VFR conditions. MVFR conditions are then favored to develop early Wednesday morning before VFR conditions return late-morning and through the remainder of the day Wednesday. Scattered showers will continue throughout the day in the vicinity of the terminal. A post-frontal convergence zone is favored to develop overnight into Wednesday, but will likely stay north of the terminal until later in the day on Wednesday. 15-25% chance of thunder as well on Wednesday, through currently confidence too low to include in the TAF.

S winds 12-15 kt with gusts 25-30 kt will continue until around 06Z Wed, after which winds will ease and begin to turn more SE overnight. SW winds prevail during the day on Wednesday at 5-10 kt.

62

MARINE

Stronger south winds continue through this evening as a weather system moves across the waters. Gale force wind gusts are expected at times for the Coastal Waters, as well as Puget Sound and Admiralty Inlet through this evening. SCA winds are expected for other waters into the evening. Onshore flow increases this evening into tonight with a strong westerly push through the Strait of Juan de Fuca. Gale Warnings have been issued for the central and eastern portions of the Strait of Juan de Fuca this evening into tonight, with gale force west wind gusts expected. Winds will slowly subside late tonight into Wednesday for the majority of waters. Northwest winds increase for the outer Coastal Waters late Wednesday before subsiding through Friday. Another weather system will approach the waters offshore over the weekend, resulting in increased southerly winds for the Coastal Waters.

Seas will build to 9 to 12 feet this evening. Seas will remain around 8 to 10 feet Wednesday before building to 10 to 13 feet Wednesday night. Seas will subside Thursday through Friday. JD

HYDROLOGY

No river flooding the next 7 days.

SEW WATCHES/WARNINGS/ADVISORIES

WA...Winter Storm Warning until 11 PM PDT Wednesday for Cascades of Pierce and Lewis Counties-Cascades of Snohomish and Northern King Counties-Cascades of Southern King County- Cascades of Whatcom and Skagit Counties.

Wind Advisory until 7 PM PDT this evening for Downtown Everett / Marysville Area-Island County-Lowlands of Western Skagit and Northwestern Snohomish Counties-Shoreline / Lynnwood / South Everett Area.

Winter Weather Advisory until 11 PM PDT this evening for Olympics.

Wind Advisory until 6 PM PDT this evening for Grays Harbor County Coast.

PZ...Small Craft Advisory until 2 AM PDT Wednesday for Grays Harbor Bar.

Small Craft Advisory until 2 AM PDT Wednesday for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca-Northern Inland Waters Including The San Juan Islands-West Entrance U.S. Waters Strait Of Juan De Fuca.

Gale Warning until 11 PM PDT this evening for Admiralty Inlet.

Small Craft Advisory until 2 PM PDT this afternoon for Puget Sound and Hood Canal.

Gale Warning until 11 PM PDT this evening for Puget Sound and Hood Canal.

Small Craft Advisory until 5 AM PDT Thursday for Coastal Waters From Cape Flattery To James Island 10 To 60 Nm- Coastal Waters From Cape Flattery To James Island Out 10 Nm.

Gale Warning until 8 PM PDT this evening for 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.

Small Craft Advisory from 8 PM this evening to 5 AM PDT Thursday for 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.