textproduct: Seattle/Tacoma

SYNOPSIS

Upper level trough remaining over Western Washington through Saturday morning. Small upper level low developing in the trough moving over the area tonight into Saturday. Trough and low move east Saturday afternoon and evening. Weak upper level ridge moving through Sunday. Upper level trough developing Monday remaining offshore. Warm front brushing Western Washington Tuesday with the trailing cold front arriving Wednesday. Front possibly stalling over the area into Thursday.

SHORT TERM /TODAY THROUGH SUNDAY/

Satellite imagery shows a combination stratus and high clouds over Western Washington early this morning. No precipitation echoes on the doppler radar. Temperatures at 3 am/10z were in the 50s and lower 60s.

Weak upper level trough over the area combined with light low level onshore flow making for a cloudy morning. Chance of showers this afternoon over the northern portion of the area while the clouds decrease over the southern portion. Highs in the 60s and lower 70s.

Upper level low moving down the British Columbia coast tonight ending up over Northwest Washington by 12z Saturday. Shower activity increasing from about Seattle northward into early Saturday morning. Mostly cloudy skies over the remainder of the area. Lows in the 50s.

Upper level low hanging out over the Northwest Interior Saturday morning before moving east of the Cascades Saturday afternoon. Showers likely north of Seattle in the morning. A little daytime heating along with the small pool of cooler air associated with the upper level producing a slight chance of thunderstorms in the afternoon over the Cascades and possibly as far west as Puget Sound with a convergence zone forming in the afternoon. Highs in the 60s and lower 70s.

Convergence zone dissipating Saturday evening. Shower activity over the Cascades drying up quickly Saturday night as the upper level trough moves east and drier northwesterly flow aloft kicks in. Low level onshore weakening overnight. With the nights getting longer these days could see some fog forming in the usual places, Southwest Interior/Cascade river valleys, by Sunday morning. Chilly morning with lows in the mid 40s to mid 50s.

Temporary upper level ridge moving through Sunday. Light low level flow in the morning giving the area plenty of morning cloud cover. Weakening front moving down the British Columbia coastline spreading high clouds over the area in the afternoon. Highs once again only in the 60s and lower 70s.

LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/

Extended models in pretty good agreement this morning. Front moving down the British Columbia coast never reaches Western Washington as an upper level trough digs offshore Sunday night into Monday. Strong upper level low moving out of the Gulf of Alaska Monday night will be off the Central British Columbia coast by Tuesday afternoon. Warm front associated with the low brushing western Washington Tuesday for a chance of showers. Highs in the 60s and lower 70s both days.

Models still showing a well organized cold front reaching Western Washington Wednesday. The new wrinkle in the solution is the associated upper level low now predicted to have a more north south track offshore on the ECMWF. This brings up the possibility of the front stalling over the area Wednesday night into Thursday. The GFS track is closer to the coast pushing the front into Eastern Washington leaving Western Washington in a cool and unstable air mass Thursday. Either way Wednesday and Thursday look wet and cool. Snow levels as low as 7000 feet by Thursday. Highs only in the 60s. There is a chance these days could be the coolest since late June/early July. Felton

AVIATION

Westerly to southwesterly flow aloft as upper level troughing remains over western Washington. VFR at terminals early this morning will be brief as incoming stratus will bring a mix of MVFR/IFR ceilings across most terminals. Could see localized LIFR along coastal terminals, and in areas of the Kitsap Peninsula. Ceilings will slowly improve by 19z-21z, with a return of VFR with mid level clouds. S/SW winds will continue generally 3 to 6 knots. Some terminal sites north of King County could see winds turn northerly in the afternoon and evening, but generally still remain light.

KSEA...VFR ceilings early this morning. Ceilings will gradually lower later this morning as MVFR stratus moves over the terminal, generally around 10z-13z. Latest guidance shows a 20-25% chance of IFR ceilings over the terminal as well, around 13z-16z. Otherwise, MVFR will continue throughout early afternoon before rebounding to VFR around 19z-21z. S/SW winds this morning may take a more N/NW later this evening but remaining light, after 00z-02z. A weak disturbance looks to trigger a Convergence Zone later this evening, and may lower conditions near KPAE at times. At this time, it should stay generally north of Everett.

Mazurkiewicz

MARINE

A weak system will cross over the area waters today for the continuation of onshore flow. Marine stratus this morning could reduce visibilities, especially along the coast. Increased southwesterlies can be expected this afternoon, along with small craft westerlies through the Central Strait of Juan De Fuca. Additional weak systems through the weekend will keep onshore flow across much of the area waters, along with another push down the Strait of Juan De Fuca on Saturday. Marine winds will become more benign late into the weekend.

Coastal seas will remain generally around 4 to 6 feet through the first half of next week.

Mazurkiewicz

FIRE WEATHER

Onshore flow, cooler temperatures, and increasing RHs will persist through next week. There still remains an isolated threat for thunderstorms Saturday afternoon mainly over the Northern and Central Cascades. If a thunderstorm develops, wetting rains are unlikely and lightning may pose a hazard that could lead to new fire starts. Erratic and gusty outflow winds over existing fires could also be problematic. Weather system next Wednesday has a good chance of producing wetting rains along the coast and over the mountains. Felton

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Small Craft Advisory from 2 PM this afternoon to 11 PM PDT this evening for Central U.S. Waters Strait Of Juan De Fuca.