textproduct: Seattle/Tacoma

UPDATE

Marine stratus is creeping into the southwest interior this evening as onshore flow steers it from west to east. Stratus will become more widespread tonight as cooler air off the Pacific filters in. Overnight lows are forecast in the upper 40s to lower 50s. The previous discussion remains below along with an updated marine/aviation section:

SYNOPSIS

Upper level ridge over Western Washington through Thursday shifting east Thursday night. Dissipating front trying to move into the area later Friday into Saturday morning. Another upper level ridge builds Saturday afternoon into Sunday. Low level flow turning onshore today with varying degrees of onshore flow through most of the week.

SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/

Strong high pressure over the Pacific NW is bringing one more warm day for western Washington, especially across the interior, with temperatures in the 70s to lower 80s. The coast is cooler and in the 60s dues to NW onshore flow. Tuesday will be similar with marine clouds and cooler conditions along the coast. Temperatures in the interior will lower a few degrees but we'll still see highs in the mid to upper 70s. High pressure remains in control moving into Wednesday, leading to more dry and mild weather. Stronger onshore pushes will bring interior temps down and few more degrees with highs in the lower 70s. 33

LONG TERM /THURSDAY THROUGH MONDAY/

Dry and mild weather will extend into Thursday due to high pressure over the region. A weak front will cross the area on Friday/Friday night for a chance of rain. However, the probabilities of exceeding 0.10" of rain over the area is low or less than 10%. Most areas may only see a trace or a few hundredths if anything. Broad high pressure rebuilds over the weekend and into early next week for another dry period of weather. Interior temperatures will track a few degrees warmer than average and in the 70s. NW winds will keep the coast cooler and in the 60s. 33

AVIATION

North to northeast flow aloft continues with an upper ridge located offshore with southwesterly surface flow 5-9 kts area wide. VFR continues in the interior for the evening. Satellite continues to track stratus pushing inland through Grays Harbor County this evening. It remains on track to reach the southern interior shortly after dusk, as well as another push through the Strait of Juan de Fuca overnight, spreading across the central interior/Puget Sound. Initial onset of the stratus will be MVFR, with IFR likely. There is a slight chance of brief LIFR in the interior, with LIFR more likely towards the coast. A return to VFR cigs are expected by mid to late morning, generally after 15Z. Surface winds will remain out of the southwest around 5 kt tonight, increasing to 5-10 kt Tuesday.

KSEA...VFR through the evening. Stratus expected to return around 06Z-10Z Tuesday, breaking out more completely after 16Z. Initial onset is expected to be MVFR, with ceilings deteriorating to IFR (slight chance of brief LIFR ceilings). Southwest surface winds 5-10 kt - diminishing to under 5 kt tonight and increasing back to 5-10 kt during the day Tuesday.

21/HPR

MARINE

A thermal trough will continue shifting inland today for a return to onshore flow. Varying degrees of onshore flow will then persist through the week as a surface ridge remains anchored offshore with lower pressure inland. Small craft advisory westerlies are likely in the central/east strait each of the next several afternoons and evenings. Additionally, low marine stratus and/or fog in the coastal waters and Strait of Juan de Fuca may reduce visibilities to mariners at times next couple mornings.

21/HPR

HYDROLOGY

No river flooding in the next 7 days.

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Small Craft Advisory until 5 AM PDT Tuesday for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca.