textproduct: Seattle/Tacoma

SYNOPSIS

Dry conditions will continue across western Washington through this afternoon. A weak system will brush the region tonight, bringing chances of light rain to the area into early Tuesday. The weather pattern becomes more active mid to late week as a series of systems brings lowland rain, mountain snow, gusty winds, and the potential for high surf to western Washington. A brief break in the unsettled weather is possible Friday night into Saturday, before the next round of unsettled weather moves in late in the weekend.

SHORT TERM /TODAY THROUGH WEDNESDAY NIGHT/

Satellite imagery shows another round of low stratus and fog developing across the interior lowlands early this morning. Expect low stratus/fog to continue to increase in extent through the early morning hours before scattering by late morning into early this afternoon. A few areas may see fog become dense, with visibilities dropping down to around a quarter mile or less at times.

Dry conditions will continue across western Washington through this afternoon as an upper level ridge pushes inland across the Pacific Northwest. A weak, splitting system offshore will then brush the region tonight into early Tuesday and will bring slight chances of showers to the area. The most likely areas to see any precipitation are the Pacific coast, Olympic Peninsula, and areas primarily north of Everett. Conditions will dry out across western Washington again by Tuesday morning, making for a another mostly dry day for many spots.

Precipitation chances will increase midweek as the first in a series of weather systems moves across the area on Wednesday. This first system will bring more widespread rain and high elevation snow to western Washington, with the bulk of the moisture focused over the Olympic Peninsula and the North Cascades. Rainfall amounts for the Pacific Coast are expected to range between a quarter of an inch to half an inch. Many spots across the East Puget Sound lowlands will get rain shadowed, with only a few hundredths of an inch expected for most areas. Snow levels generally hovering near 5500 ft will bring a few inches of snow to the higher peaks of the Olympics and North Cascades. Winds will also increase as this system approaches the area, with southerly winds expected to pick up along the coast during the late morning to early afternoon hours and increasing across the interior during the evening hours. Winds will be the strongest along the Pacific Coast, with the most likely scenario at this time highlighting wind gusts reaching 25-35 mph. Winds across the interior will increase to 10-20 mph, with gusts to 25-30 mph possible. Winds will ease again overnight into Thursday.

LONG TERM /THURSDAY THROUGH SUNDAY/

Precipitation will gradually taper across the area during the day on Thursday, however a stronger system will move into the area Thursday night into Friday. This system will bring another round of gusty winds, lowland rain, high elevation snow, and the potential for high surf along the Pacific Coast. The bulk of the moisture with this system will remain aimed at the Olympic Peninsula and the North Cascades, with the highest rainfall amounts likely being along the North Coast, where half an inch to an inch of rain is expected. Many areas across the interior lowlands will be rain shadowed again and generally look to receive a couple hundredths of an inch to a quarter of an inch of rain. Snow levels between 4500-5000 ft will bring some additional snowfall to the higher peaks of the Olympics and North Cascades. Winds will become gusty as the system approaches, with latest probabilistic guidance indicating a 50% chance of wind gusts exceeding 40 mph along the Pacific Coast and a 40-50% chance of wind gusts exceeding 40 mph for areas from Whidbey Island northward. Increasing potential for high surf along the coast could also bring localized beach erosion to coastal communities and create hazardous conditions for beachgoers.

Ensemble clusters continue to hint at a brief break in the unsettled weather Friday night into early Saturday as a ridge of high pressure temporarily moves back over the region. Discrepancies remain in regards to the amplitude of the ridge over the area at this time, however it does look to aid in directing the bulk of the moisture of the next incoming system more into British Columbia. The ridge does look to push inland rather quickly though, which would open the door for the system impacting British Columbia to move into the area by Sunday.

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AVIATION

High pressure will slowly drift east with a weak front remaining offshore through the period. Satellite and cameras this morning shows a mix of low MVFR or IFR stratus, and patches/areas of fog. The stratus is generally confined to the south interior, where areas to the north in Puget Sound and the north interior are seeing instances of fog (which has been thin in vertical depth). Thought process is once high clouds build in ahead of an offshore front, the fog will shut down going into the 16-19Z timeframe. The coastal terminals have a 20 percent chance of showers later this afternoon and evening. Remaining terminals will likely stay dry. Higher clouds likely remain overnight tonight, and keep low ceiling/fog potential limited to the south interior. Winds at the surface will generally flow out of the southeast, with winds of 5-10 kt in the mountains/coast, and 5 kt or less in the interior.

KSEA...Vicinity fog in progress this morning. The greatest chance of restrictive visibilities is from 10-14Z as fog continues to grow and spread across the area. High clouds filling later this morning likely shuts off the fog/low stratus threat sometime later this morning from 16-19Z, with VFR conditions for the remainder of the TAF period. Light southeast winds at 5 kt or less.

HPR

MARINE

High pressure will slowly drift eastward today with a front remaining offshore in the coastal waters. This will result in some breezy winds in the far outer coastal waters up to 20 kt. The pattern will become active again from Wednesday through the weekend as an atmospheric river pattern begins to take shape, The first system on Wednesday will primarily bring wind impacts to the coastal waters, with a 60-80% chance of winds gusts over 20 kt. The next system on Friday will be stronger, with gusty winds covering the coastal and the interior waters as southerly winds increase with the system passing through. There is a 25-40% chance of gale gusts in the coastal waters and the east Strait of Juan de Fuca. 2 additional systems may also impact the waters through the weekend and early next week, with again chances for wind gusts over 20 kt.

A small craft advisory continues for seas of 8 to 11 ft in the coastal waters/west Strait of Juan de Fuca. Seas will decrease to 6- 8 ft on Tuesday before building back to 10 ft to 13 ft Thursday, and further increase to 15 to 20 ft on Friday before decreasing back to 11 to 15 ft next weekend.

HPR

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Small Craft Advisory until 1 AM PST Tuesday 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-West Entrance U.S. Waters Strait Of Juan De Fuca.