textproduct: Seattle/Tacoma

SYNOPSIS

An upper-low will exit the region tonight as an upper-ridge replaces it. Ridging looks to remain in place to start the week before a well-organized system arrives on Wednesday and lead into Thursday with the potential for widespread rainfall. This disturbance will remain in the vicinity through the weekend keeping conditions cool and unsettled.

SHORT TERM /TONIGHT THROUGH MONDAY NIGHT/

The upper-low that brought widespread showers and isolated thunderstorms earlier today has now crossed the Cascades. A few showers remain over the west slopes of the Cascades but conditions are beginning to trend drier. An upper-ridge offshore is slated to build in later tonight as straggling shower activity wanes. Lingering surface moisture from recent precipitation will likely lead to areas of low clouds and fog developing into early Sunday morning. Overnight lows tonight will bottom into the mid 40s to mid 50s.

Sunday and Monday are panning out to be really nice days. Areas of fog and low clouds will start off for both (more so on Sunday) but gradual clearing should eventually give way to some sunshine. High clouds are favored to pass overhead at times but nonetheless conditions are to remain dry via large-scale subsidence with upper-ridging in place. Highs to start the week will rise into the 60s and 70s but areas in the southwest interior could top out near 80 F on Monday. Overnight lows mainly in the 50s but a few spots could settle into the 40s.

LONG TERM /TUESDAY THROUGH SATURDAY/

Guidance has an upper trough and its associated low digging further offshore now than previous runs. As a result, subtle ridging upstream of it may keep conditions relatively drier on Tuesday than previously thought. Though, shower chances remain but more widespread precipitation is favored on Wednesday and Thursday as a well-organized disturbance remains on track to enter the region. Too early to tell estimates are bringing between 1.00-3.00" of rain for the coast and Olympics in a 30 hour period ending early Thursday morning with more QPF expected to fall throughout the remainder of the day. Interior locations are so far ranging between 0.50-1.00". The upper-trough will maintain over the region through Saturday as it's sandwiched between two areas of upper-ridging. Cool and unsettled conditions trending into the weekend as temperatures measure well-below normal.

AVIATION

An upper level low will track to the east of the area tonight, keeping northwesterly winds aloft. A scattered cloud deck with VFR ceilings remains over much of western Washington, with showers confined mostly to the mountains this evening. Clouds look to remain scattered through this evening before they begin to fill in once again overnight. The areas most likely to see lower ceilings are along the coast and from Everett northwards (40-60% chc), while around Seattle and southwards probabilities are less certain (35-40%). Most terminals will likely see at least some MVFR cigs by sunrise on Sunday. Terminals such as PAE and PWT may see some brief periods of fog tomorrow morning as well. Clouds look to scatter form south to north Sunday afternoon, but mid and upper level clouds may impede scattering, especially across the northwestern most portions of the area.

Winds generally remain south-southwesterly tonight and into Sunday. Areas around PAE and the north-central Puget Sound may briefly turn northerly this weekend. A full shift to N in the Sound is more probable Sunday evening.

KSEA...VFR conditions will continue through this evening. Areas of low clouds look to develop Sunday morning, but will lean on more of an MVFR stratus threat for SEA. Clouds look to lift and scatter by Sunday afternoon. Winds look to remain southwesterly 4-8 kt, and may begin to turn northerly approaching 00Z Mon. 33/62

MARINE

Another westerly push down the Strait of Juan de Fuca this evening will likely create Small Craft Advisory winds this evening. Afterwards, weak frontal systems passing by to the north tomorrow into Monday and early Tuesday will keep high pressure well offshore, allowing winds to remain mostly light across the area waters. A stronger low pressure system looks to move in from the north Tuesday night into the middle of next week, which will bring the first fall- like system with increased southerly winds across all the area waters. There is a 60-70% chance of gusts reaching up to gale force through the east entrance to the Strait of Juan de Fuca and the inner coastal waters on Wednesday.

Seas remain around 3-6 ft until Wednesday, rising up to around 8-11 ft then as the system moves through. 62

FIRE WEATHER

A cooler and more moist airmass will remain in place for the majority of the week. A stronger system arriving Tuesday night into Wednesday will bring with it abundant rainfall to the coast and Cascades. One to three inches of rain are forecast in the Olympics, and between 0.75"-1.00" of rain is expected in the lowland and Cascades. This will ease fire weather concerns for the near future as fuels respond to wetter conditions.

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SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Small Craft Advisory until 1 AM PDT Sunday for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca.