textproduct: Seattle/Tacoma

SYNOPSIS

Cooler temperatures and increased chances for precipitation arrives Tuesday through midweek. Warmer and drier conditions look to return later through the week and into the weekend.

SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/

Mid and high clouds are increasing across Western Washington this evening associated with an upper low offshore of Oregon/California. Generally dry conditions tonight with showers increasing on Tuesday. No major forecast updates this evening, previous discussion below.

A deep upper level low continues to meander offshore and will shift further inland on Tuesday, allowing for wrap around moisture to move into western Washington. This will allow for showers to move northward throughout the area on Tuesday and for cooler temps in the upper 50s and lower 60s. There will also be instability from the aforementioned upper level low, so we could see some isolated thunder Tuesday afternoon/evening, but mainly confined to the Cascades. Snow levels will remain above 5000 to 6000 feet with minimal accumulating snow over the higher peaks.

This trend continues into Wednesday with scattered showers across most of the area and high temperatures in the mid 50s.

LONG TERM /THURSDAY THROUGH MONDAY/

Shower activity will decrease heading into Wednesday night as an upper level ridge develops offshore. Ensemble guidance shows a warming and drying trend through the end of the week and heading into the weekend, with temperatures warming back up into the upper 60s and potentially low 70s. Models do show some disagreement on the strength of the ridge and how long the conditions remain dry for.

Mazurkiewicz

AVIATION

Southerly flow aloft will continue into Tuesday as a cutoff upper level low off the northern California coast gradually shifts eastward. A combination of developing low level onshore flow and moisture wrapping around this system will lead to increasing shower activity along with lowering ceilings across the area on Tuesday. Ceilings are expected to lower to MVFR along the coast overnight then spread northward across interior areas Tuesday morning. These conditions will then persist into Tuesday night and beyond.

KSEA...VFR conditions will continue into this evening. Ceilings will lower overnight and are expected to become MVFR by around mid- morning Tuesday with showers in the vicinity of the terminal by afternoon. Surface winds will become S/SW 4 to 8 knots with gusts near 15 kt tonight and continue overnight. Winds will rise to 10 to 15 knots at times Tuesday morning. 27/41

MARINE

Weak low pressure will remain over the inner coastal and interior waters into midweek with broad high pressure remaining well offshore. A modest increase in onshore flow on Tuesday is expected to produce small craft advisory winds in the central and east portions of the strait. Gusty north to northwesterly winds and steepening seas are expected over the outer coastal waters on Wednesday. Winds ease, seas subside and the flow turns more northerly late this week in response to a strengthening surface ridge over British Columbia. 27

HYDROLOGY

No river flooding is expected over the next 7 days.

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Small Craft Advisory from 3 PM to 11 PM PDT Tuesday for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca.