textproduct: Seattle/Tacoma

SYNOPSIS

Cold front east of the area early this morning. Atmospheric river to the south lifting north over Western Washington this afternoon with the river remaining over the area Friday. Upper level ridge building offshore will pinch off the river and push it south Friday night. Weak upper level trough Saturday keeping showers in the forecast. Warm front moving over the top of the ridge brushing Western Washington Sunday. Atmospheric river aimed at Southern British Columbia the first part of next week with the southern portion of the river over the area. Warming trend beginning Monday into the middle of next week.

SHORT TERM /TODAY THROUGH SATURDAY/

First a word about the blizzard warning. While the forecasted winds developed the snow did not materialize. The cold front was a few hours behind schedule keeping the warmer air over the Cascades for a longer period of time allowing the snow levels to climb above Stevens and Snoqualmie Pass last night and remain above pass levels into the morning hours. The colder air is arriving now ( 3 am ) with the temperature at Stevens Pass back below freezing. Snoqualmie Pass will follow suit in a few more hours with the precipitation turning back to snow in the passes. At this point the winds are starting to ease so the blizzard warning has been cancelled. The winter storm warning is still in effect for today into Friday evening. It's certainly not going to be an easy go across the Cascades today through Friday.

Satellite imagery shows the cold front east of the Cascades early this morning. Doppler radar has plenty of showers over the area with a bit of a rain shadow over the Central Puget Sound with the strong westerly flow aloft. Convergence zone hanging out over Snohomish county. Temperatures were in the 40s at 3 am/10z with all of the wind gusts over the lowlands less than 30 mph.

Post frontal shower activity continuing this morning. Atmospheric river aimed at Western Oregon will lift to the north this afternoon spreading steady rain back over the area. Winds will continue to ease throughout the day. Snow levels dropping with Western Washington remaining slightly on the cool side of the jet. By this afternoon snow levels will be back down to 1000 to 2000 feet in the Cascades. Highs will be cool, in the lower to mid 40s.

Little change in the pattern tonight into Friday with the Western Washington remaining on the north side of the atmospheric river. Forecast gets a little tricky late tonight into Friday morning as the air mass continues to cool. Onshore surface gradients going light. Snow levels getting down to around 500 feet by sunrise Friday. This brings up the possibility of a rain/snow mix for the precipitation type late tonight into early Friday morning. Daytime "heating" warming the air mass up in the afternoon to lift snow levels back up to at least 1000 feet. Could an inch or so of snow in the Cascade foothills in the morning hours Friday. Lows in the mid 30s. Highs in the lower to mid 40s.

Atmospheric river moving south Friday night as an upper level ridge builds offshore. Cooler air mass moving into the area with the snow level down to the surface in many locations by early Saturday morning. At this point it is the game we play frequently around here with the moisture decreasing as the air mass cools. Precipitation type changing to showers overnight making snow accumulation forecast tough. If there is enough moisture around as the snow levels lower to near the surface could see some small snow accumulations. With the precipitation being showers lowland snow will be localized and not widespread. Lows in the upper 20s to mid 30s.

Cool northwesterly flow aloft Saturday with the upper level ridge axis well offshore. Models showing a weak trough embedded in the flow aloft moving through during the day keeping showers in the forecast. Snow levels will be low but once again with limited moisture if there are any snow accumulations in the lowlands they will not be widespread and will be early in the day. Like Friday daytime heating will lift the snow level back up to at least 1000 feet in the afternoon. Highs in the mid 40s.

LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/

Extended model solutions have been consistent with the general pattern solution of an upper level ridge offshore and an atmospheric river moving over the top of the ridge. Where the river moves inland has been bouncing around a bit but the general consensus is it will move inland over Vancouver Island and Southern British Columbia. There is also good consensus that the ridge will not be strong enough to keep the tail end of the river north of Western Washington Sunday through Tuesday giving Western Washington a rain at times or rain likely forecast. Some of the solutions for Wednesday drop the weakening atmospheric river over Western Washington. Confidence not real high at this point so will stay with the rain likely or rain at times forecast. Warming trend next week with the area being on the south side of the jet. Highs near 60 for both Tuesday and Wednesday. Snow levels rising significantly ending up in the 7000 to 8000 foot range. Felton

AVIATION

Majority of terminals VFR early this morning with a few locations MVFR as light scattered showers move across the region. Another system will impact the terminals today, bringing steadier rain after 14z. Widespread MVFR cigs/vis expected after 16z-20z. IFR cigs possible (20-40% chance) after 00z, with the highest chances for the coast, Kitsap Peninsula, and southern interior. Breezy SW winds will continue this morning with gusts to 20-25 kt, with the gusts expected to subside by the evening.

KSEA...VFR cigs this morning, with cigs/vis expected to deteriorate this afternoon after 20z. Stratiform rain expected to arrive at the terminal by 17z. Guidance hints at a small chance (20%) of IFR cigs after 06z, with probabilities slightly increasing to 30% after 16z. Breezy SW winds continue at the terminal early this morning with gusts 20-25 kt. Winds will ease throughout the day, with winds decreasing to 5-10 kt by the evening hours.

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MARINE

The latest observations show winds have been on a decreasing trend early this morning and the Storm Warning for the East Strait of Juan de Fuca has been downgraded to a Gale Warning. Conditions will remain breezy along the Strait of Juan de Fuca this morning through this evening, for which a Small Craft Advisory will follow the Gale Warning. In addition, the Gale Warnings for Puget Sound, Admiralty Inlet, and the Northern Interior waters have been downgraded to Small Craft Advisories. Seas early this morning are hovering around 12-14 ft and are expected to continue decreasing throughout the day, with seas around 8-10 ft by the afternoon hours. A weak front will stall over the coastal waters today and Friday, with surface winds shifting northerly Friday morning through the weekend. Brief small craft gusts possible (45-65%) for the outer coastal waters on Saturday. Seas are expected to remain below 10 ft through the weekend. A warm front will move over the waters on Monday. Seas may build near 10 ft. In addition, there is moderate chance (40-60%) of small craft winds for the coastal waters.

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HYDROLOGY

The Skokomish River went above flood stage overnight and will crest this morning. The river will recede back below flood stage later today. More rain in the forecast through Friday will keep the threat of flooding along the Skokomish Friday into Saturday. With the heaviest precipitation over the Southwest Interior there is also a threat of flooding Friday into the weekend for a few rivers in the Chehalis Basin including but not limited to the Skookumchuck, Newaukum and the Chehalis River from Grand Mound to Grays Harbor. The flooding threat will ease Sunday into next week for the southern portion of the area. Atmospheric river forecasted to move inland to the north during the first part of next week. If the river ends up a little further south rivers over the northern portion of the area will bear watching the first part of next week. Felton

SEW WATCHES/WARNINGS/ADVISORIES

WA...Winter Storm Warning until 5 AM PDT Saturday for Cascades of Pierce and Lewis Counties-Cascades of Snohomish and Northern King Counties-Cascades of Southern King County- Cascades of Whatcom and Skagit Counties-Olympics.

PZ...Small Craft Advisory until 2 PM PDT this afternoon for Admiralty Inlet-Grays Harbor Bar-Northern Inland Waters Including The San Juan Islands-Puget Sound and Hood Canal.

Gale Warning until 8 AM PDT this morning for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca-West Entrance U.S. Waters Strait Of Juan De Fuca.

Small Craft Advisory from 8 AM this morning to 5 PM PDT this afternoon for Central U.S. Waters Strait Of Juan De Fuca- East Entrance U.S. Waters Strait Of Juan De Fuca-West Entrance U.S. Waters Strait Of Juan De Fuca.

Small Craft Advisory until 11 PM PDT this 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.