textproduct: Seattle/Tacoma

SYNOPSIS

High pressure will nose into the area today for warmer afternoon temperatures and sunny skies. The next chance for rain will be on Friday and Saturday as a frontal system moves through the region. Cooler temperatures will linger in the wake of this system into early next week.

SHORT TERM /TODAY THROUGH SATURDAY/

Areas of fog and stratus are present on the satellite imagery early this morning from King County north along the water and along the Pacific coast. The fog and stratus should be less extensive this morning compared to the last few days. Once this dissipates later this morning, afternoon high temperatures will climb to the low to mid 70s.

The warm conditions are short lived as a weak frontal system will be arriving Friday into Saturday and will usher in a pattern change. The front isn't expected to be strong, but will bring about a round of rain to western Washington as well as breezy southwesterly winds throughout the Puget Sound region. Westerly wind will also be elevated through the Strait of Juan de Fuca. The QPF is expected to be around a quarter to half inch in the Cascades, with a few hundredths to a tenth elsewhere. This is going to be a cooler system, so the snow levels will fall to around 4,500-5,000 ft Friday night into Saturday and bring an inch of snow or less primarily to the North Cascades. Saturday morning lows will be in the low 40s for much of the Puget Sound area, but in the Cascades and adjacent foothills, lows in the mid to upper 30s are expected.

LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/

Drier but cooler conditions are expected Saturday night into Sunday. Sunday morning lows will be a bit cooler than Saturday with much of the area seeing the upper 30s and low 40s. Sinking cold air in the Cascade valleys could drop the lows down to around freezing. The probabilities for seeing lows 32 degrees or less for Sunday morning are about 30%, most notably in the Cascade valleys of Snohomish and Skagit Counties as well as the Mount Rainier area. This will be of note for frost and freeze impacts for the agricultural realm and for those with sensitive vegetation. The lows increase into Monday and beyond, but the afternoon highs through the middle of the week will be in the low to mid 60s.

The ensembles generally favor west CONUS troughing through Wednesday, with another chance at some light rain come Tuesday. Things start diverging in the models a little bit after Wednesday in a competition between the trough lingering and high pressure attempting to return to the area.

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AVIATION

Northwesterly flow aloft will become more westerly by this evening as an upper ridge over the area flattens and an upper trough drops down into British Columbia. Another round of fog/ low stratus will be the main concern for area terminals this morning, with latest satellite imagery already showing fog present along the Pacific Coast, portions of the central Sound, and across the North Interior. Conditions across the area terminals remain predominantly VFR as of 08Z, but expect the extent of fog to continue to expand over the next few hours. Conditions will likely deteriorate to IFR/LIFR for any terminals in fog. With the layer of moisture being shallower than previous days, expect fog and low clouds to scatter out by 18Z. VFR conditions will then prevail this afternoon and evening, with only high clouds streaming in overhead ahead of a frontal system on Friday. Light and variable winds this morning will pick up from the north and persist between 5-10 kt this afternoon and evening.

KSEA...LIFR conditions persist this morning with fog at the terminal. Conditions will gradually improve through the morning hours, with fog expected to scatter by 18Z for a return to VFR conditions. Winds are light and variable this morning, but will pick up from the north at 5-10 kt this afternoon and evening.

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MARINE

Fog is the primary marine impact over the area waters early this morning as areas of dense fog have developed along the Pacific Coast and across much of the inner waters. Expect areas of fog to reduce visibilities down to 1NM or less through the early morning hours. Visibilities will then improve as fog scatters mid to late morning.

High pressure will remain situated over the coastal waters today while a thermal trough pushes inland. The return of onshore flow will bring small craft westerlies to the central and eastern Strait of Juan de Fuca this afternoon and evening. A frontal system will then move across the area waters on Friday, bringing gusty winds and building seas. The northern and central coastal waters and the Strait of Juan de Fuca will likely see the strongest winds, with latest REFS guidance indicating roughly a 50-75% chance of gusts exceeding 34 kt across the coastal waters and a 30-50% chance of gusts exceeding 34 kt along the central and eastern Strait. As guidance has continued to trend upward, have gone ahead and issued Gale Watches for these areas. Seas will build in the system's wake, with latest GEFS probabilities indicating a 60-80% likelihood of seas exceeding 12 ft across the coastal waters by Friday night.

Winds will ease and seas will gradually subside through the day on Saturday as the system exits the area. High pressure will then build back into the coastal waters by Sunday, while a thermal trough expands northward along the coast. This pattern will persist into Monday, bringing periods of offshore flow back to the area waters. Seas will persist between 5-8 ft. The next frontal system then looks to move into the area waters on Tuesday.

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SEW WATCHES/WARNINGS/ADVISORIES

WA...Dense Fog Advisory until 10 AM PDT this morning for Grays Harbor County Coast-Northern Washington Coast.

PZ...Small Craft Advisory from 2 PM this afternoon to 3 AM PDT Friday for Central U.S. Waters Strait Of Juan De Fuca- East Entrance U.S. Waters Strait Of Juan De Fuca.

Gale Watch from late tonight through Friday evening for Central U.S. Waters Strait Of Juan De Fuca-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-East Entrance U.S. Waters Strait Of Juan De Fuca.

Dense Fog Advisory until 10 AM PDT this morning for Admiralty Inlet-Coastal Waters From Cape Flattery To James Island Out 10 Nm-Coastal Waters From James Island To Point Grenville Out 10 Nm-Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm-East Entrance U.S. Waters Strait Of Juan De Fuca-Northern Inland Waters Including The San Juan Islands-Puget Sound and Hood Canal.