textproduct: Seattle/Tacoma

SYNOPSIS

An upper level ridge will remain situated over Western Washington through Thursday. Onshore flow will continue throughout the week, leading to additional rounds of morning marine stratus over the next days. A weak frontal system will move over the area on Friday, bringing a small chance of showers to the coast and mountains. An upper level ridge will rebuild over the area this weekend into early next week, leading to a gradual warm up in temperatures.

SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/

Temperatures will continue to slowly lower, but given the trend of the stratus stuck in place, low temperatures will likely remain relatively warm compared to forecast, in the low 50s.

An upper level ridge will remain in place over Western Washington through Thursday. Onshore flow will keep stratus over the region into Thursday morning, with guidance suggesting clouds scattering out in the afternoon. Therefore, slightly warmer tomorrow with high temperatures in the mid to upper 50s along the coast and mid to upper 60s in the interior. Cloud cover will be reintroduced Thursday evening as the next system heads towards the region.

On Friday the ridge axis will push east as a shortwave trough moves through the region, which will be accompanied by a weakening cold front. Not much expected in terms of precipitation with this frontal system. Majority of locations are expected to remain dry. The locations that have the highest chances of seeing precipitation will be limited to the coast and mountains, with current PoPs at 10% or less.

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LONG TERM /SATURDAY THROUGH WEDNESDAY/

Ensemble guidance is in good agreement that an upper level ridge will rebuild over Western Washington this weekend and likely persist into early next week. The ridge will keep strengthening into early next week, leading to a gradual warm up. The latest guidance suggests high temperatures this weekend will be in the low 60s along the coast and mid 60s to low 70s along the interior. Temperatures early next week through midweek will warm up to the mid 60s along the coast. Temperatures along the interior will be in the mid to upper 70s, with 80s possible in the southwest interior. 29

AVIATION

High pressure remains in place over the region. Low level onshore flow continues, which has maintained a fairly extensive stratus deck through the lowland. Near the surface, low level onshore flow continues with stratus clouds covering much of the lowlands. Most areas are within MVFR range. Clouds will lower overnight with pockets of IFR conditions. Weaker onshore pressure gradients will help low clouds to lift and scatter in the interior Thursday afternoon.

KSEA...MVFR ceilings remain in place. Brief IFR conditions possible Thursday morning. Improving conditions after 21Z. S/SW winds to 10 kt.

MARINE

Surface high pressure is over the offshore waters with lower pressure inland, resulting in ongoing onshore flow over western WA. Steep seas persist over the northern-most coastal waters with seas 8- 10 ft with a dominant period of 8 to 10 seconds, but seas will begin to ease early Thursday morning. Winds through the Strait have also be slightly lower that previously forecast, so confined the advisory to the central Strait through early Thursday morning.

Onshore flow is weaker on Thursday. A weak front will cross the waters on Friday. Expect light winds over the waters on Saturday with a stronger onshore pushes Saturday night and Sunday night.

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HYDROLOGY

The daily hydrology discussion has ended until the start of the next rainy season; it will only be updated during this time as needed.

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Small Craft Advisory until 5 AM PDT Thursday 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.