textproduct: Seattle/Tacoma

SYNOPSIS

Drier and slightly cooler weather will prevail across western Washington this weekend into Monday with high pressure. A dissipating system will arrive Saturday night into early Sunday, bringing chances for light rain to the northwestern areas. A stronger low pressure system will bring rain, higher- elevation mountain snow, and gusty winds across the area Tuesday into Wednesday.

LONG TERM /MONDAY NIGHT THROUGH FRIDAY/

Active weather will begin to return on Tuesday as a shortwave trough develops over the northeast Pacific and moves northwestward into British Columbia. This will allow for a strong low pressure system to develop over the northeast Pacific and then push northwestward into the Pacific Northwest. Models differ on the exact track of this low--whether the center will track closer to Vancouver Island or whether it will drift farther north towards Haida Gwaii--but a wetter, winder system will be on track to impact the area Tuesday into early Wednesday. Since it will be fast moving, it will not be a hydrologically significant system with 0.5-1" expected across much of the area. Southwesterly winds will increase across the area Tuesday, peaking Tuesday evening, before decreasing later on Wednesday. There is a 50- 65% for gusts to exceed 45 mph for portions of the Pacific coast and the north interior north of Island/Skagit co.s. Snow levels above 4000 ft will likely mean that the system will be mostly rainfall in the passes on Tuesday. Snow levels will lower late Tuesday but as precipitation decreases snow accumulations at the passes will be limited but non-zero through Wednesday. The active pattern looks to continue into the late week timeframe with additional, albeit weaker, systems moving through the area. Temperatures will largely be consistent during the long term period, with high temperatures in the low to mid 50s and low temperatures in the low to mid 30s.

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AVIATION

West flow aloft will prevail with mostly zonal flow and an embedded shortwave moving through late tonight. MVFR cigs prevail across much of the central Puget Sound terminals with weak but broad post-frontal convergence is keeping ceilings lower. Elsewhere, VFR conditions prevail with mid to upper level clouds slowly clearing. Clouds over the Puget Sound will persist through much of the morning but slowly begin to clear through the afternoon with ceilings lifting to VFR across the entire area. Lower ceilings will begin to return tonight into early Sunday morning as a dissipating cold front arrives across the area.

Winds this morning mostly light with the exception between Seattle and Whidbey Island where west to north winds continue to push out of the Strait of Juan de Fuca. Winds will generally remain west (or north through the Puget Sound) through this afternoon, when more southwest to south winds begin to prevail between around 00-06Z Sun, though generally 5 kt or less by this time.

KSEA...MVFR cigs this morning under broad post-frontal convergence. Ceilings will gradually lift and scatter through the morning, around 17-20Z. VFR conditions prevail through the remainder of the TAF period. Lower ceilings return after 12Z Sun. N/NE winds 8-12 kt will become southerly from 23-02Z this evening.

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MARINE

Winds will continue to subside across the area, with the strongest winds lingering through the Strait of Juan de Fuca into Admiralty Inlet. These winds will ease later this morning below thresholds. Rather tranquil conditions will prevail over the waters for much of today. A weakening surface front will approach the northwestern waters tonight and may briefly increase winds to near Small Craft Advisory thresholds (40-50% probability between around 6PM - midnight Sunday). The front will dissipate as it moves across the area early Sunday morning, with high pressure filling in its place. This will remain in place until Tuesday when a stronger low pressure is expected to move into the region. These remains uncertainty on the exact of this system, with the level of impacts differing whether the low center hugs closer towards Vancouver Island or if to moves farther north towards Haida Gwaii, but expect stronger winds and seas with this system. The most likely solution has winds reaching gale force across the coastal waters with seas reaching into the 15-18 ft range. The GEFS shows a 30-50% chance of seas exceeding 18 ft across the northwestern portions of the coastal waters by early Wednesday. The system will northwest with the surface front traversing the coastal waters Tuesday evening.

Seas today around 6 to 8 ft will remain like so through the weekend and into early Monday until seas rise with the aforementioned system Tuesday into Wednesday, likely above 15 ft.

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HYDROLOGY

Active warnings are in effect and rivers will either crest or continue to recede today. Additional flooding is not anticipated on rivers not already warned and therefore the Flood Watch has ended. Rivers will continue to recede through Monday. A wetter system will bring small rises Tuesday and Wednesday but additional flooding is not forecast as this time.

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Small Craft Advisory until 7 AM PDT this morning for Admiralty Inlet-Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca.