textproduct: Seattle/Tacoma

SYNOPSIS.

Weak high pressure will bring dry conditions today. Active weather returns on Tuesday for more rain, high elevation snow and gusty winds. Showers and a convergence zone will form on Wednesday with onshore flow. Drier weather will prevail late in the week and into the weekend.

SHORT TERM /TODAY THROUGH WEDNESDAY/

Weak high pressure is over the area today for dry conditions. Temperatures will be mostly in the 30s this morning with freezing temps around the south sound. Expect highs in the lower to mid 50s this afternoon (near normal) with increasing clouds during the evening.

A strong and wet Pacific frontal system will impact the area on Tuesday. This system is tied to a deep low spinning offshore that will shift north of Vancouver Island. The main threat will be gusty south winds, primarily coast and north interior, where probabilities of gusts exceeding 45 mph are the highest. Up in the mountains, snow levels are lowest over the northern Cascades where a few inches of snow will fall. Snow levels will be rising over 6,000 ft in the central Cascades thus minimizing impacts to I-90 and US 2. Rivers will see small rises but additional flooding is not anticipated.

We remain under moderate onshore flow on Wednesday with high pressure offshore and deep low pressure to our north. Snow levels are lower, around 2,500 ft, with snow in the Cascades and passes. Showers with a convergence zone may enhance snow amounts near Stevens Pass. The air mass is slightly unstable with isolated thunderstorms possible too. 33

LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/

High pressure shifts inland on Thursday with the flow turning offshore. This pattern will persist through the weekend for slightly warmer and dry weather. Highs in the interior will reach the lower 60s Friday and Saturday. A trough kicks the ridge inland on Sunday with slightly cooler temps and a chance of rain. 33

AVIATION

Zonal flow will continue to prevail across western Washington today. VFR conditions will prevail for much of the TAF period with high clouds continuously overhead. Lower ceilings will begin to reenter the forecast after around 06Z Tue as a warm front begins to arrive along the coast. The best chances of seeing MVFR cigs by 12Z Tue will be along the Pacific coast and portions of the north interior (incl. BLI), probabilities around 25-50%. Winds calm to light northerly this morning, remaining northerly up to 4-8 kt through the day.

KSEA...VFR conditions through the period with high clouds overhead. Ceilings begin to redevelop and lower but remain VFR after 06-12Z Tue. Winds north 6-10 kt through the period.

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MARINE

Broad high pressure over the region will maintain relatively light winds and seas in the 7 to 9 ft range today. A developing low pressure currently in the north-central Pacific around 35 N/150 W will move northwestward, reaching the area early Tuesday. The low center will track up towards the northern point of Vancouver, with the associated cold front moving across the Washington coastal waters Tuesday evening. Winds will start to increase across the area early Tuesday morning. Winds peak first across the coastal waters Tuesday afternoon ahead of the frontal passage, then subsequently through the interior waters later Tuesday evening. Guidance continues to indicate that gale force winds will be likely across the coastal waters, as well as through the Puget Sound, Admiralty Inlet, and into the East Entrance to the Strait of Juan de Fuca. All of these locations continue to be under a Gale Watch through early Wednesday morning. Elsewhere, winds will likely meet Small Craft Advisory thresholds on Tuesday. Winds will likely remain a bit elevated for much of Wednesday as strong onshore flow continues behind the system. Calmer conditions look to prevail Thursday through the end of the week as high pressure looks to redevelop across the area. In addition to winds, seas will rise on Tuesday, peaking around 15-18 ft, with seas up to and exceeding 20 ft possible across the northwest outer waters. GEFS guidance continues to show a 40-60% chance of seas exceeding 20 ft, with the highest chances over the outer northwestern-most waters. Seas will slowly subside through the day Wednesday, becoming 6-8 ft Thursday through the rest of the week.

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HYDROLOGY

Flows on the Cedar River at Renton remain high, just below Minor Flood Stage, due to dam operations. Otherwise, rivers will continue to recede today. Small rises are expected with Tuesday's wetter system however additional flooding is not expected. 33

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Gale Watch from Tuesday morning through Tuesday afternoon for Admiralty Inlet-East Entrance U.S. Waters Strait Of Juan De Fuca.

Gale Watch from Tuesday morning through Tuesday evening for Puget Sound and Hood Canal.

Gale Watch from late tonight through Tuesday evening for Coastal Waters From Cape Flattery To James Island 10 To 60 Nm-Coastal Waters From Cape Flattery To James Island Out 10 Nm-Coastal Waters From James Island To Point Grenville 10 To 60 Nm-Coastal Waters From James Island To Point Grenville Out 10 Nm-Coastal Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm-Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm.