823 FXUS66 KSEW 121034 AFDSEWArea Forecast Discussion National Weather Service Seattle WA 334 AM PDT Sun Oct 12 2025
.SYNOPSIS...Cool and unsettled conditions will continue across Western Washington today as a system moving southward tonight brings the first noteworthy high elevation snow of the season to the area. Drier conditions return by Tuesday with weak high pressure over the area through midweek. Another disturbance likely brings cooler and cloudier conditions and another round of precipitation late in the week.
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.SHORT TERM /TODAY THROUGH TUESDAY/...A lingering convergence zone has steadily weakened overnight and early this morning, with the lingering remnants moving east near a Sultan to North Bend line. This will continue to push east and fade out toward daybreak. Elsewhere, a few areas of showers remain in the onshore flow, but a bit of a temporary lull in between these two weather systems within the broad upper trough. This next disturbance will drop south from British Columbia today, maintaining more widespread showers and lowering snow levels that will bring snow in the mountains. Expect the largest snow totals above 5000 feet at places like Mount Baker and Paradise on Mount Rainier, with some accumulations down to 3000 ft or so in the North Cascades and around Stevens Pass in the central Cascades, where a 2-4 inches of snow may fall through Monday morning. While accumulations are unlikely at Snoqualmie Pass, some snow mixing in with rain down to pass level is possible. This will be the first notable snowfall of the season in the mountains, and those heading into the higher Cascade elevations should be prepared for snow and colder conditions.
As this upper low tracks south off the Oregon coast and down to California, expect to see an increase in offshore flow and Fraser outflow setting up across western Whatcom County and across the San Juan Islands with gusts up to 40-45 mph. Breezy northerly winds across other portions of the interior may follow early Monday morning, but only topping out closer to 25 mph in these other locations. This disturbance pushing away from the area will also bring a drier trend and decreasing cloud cover. This will lead to rather cool nights, especially as the air mass dries cools efficiently, with some potential for frost starting Tuesday morning. 12
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...As mentioned above, There`s potential for frost in some of the outlying, sheltered location both Tuesday and Wednesday mornings, with even around a 15% chance for some of the cool spots south of Olympia through Centralia and west toward Aberdeen approaching the freezing mark for an hour or three on Wednesday morning. Daytime highs will reach into the lower 60s with mostly sunny skies through the midweek period. Ensemble guidance then begins to split late in the week with the potential for at least a weak system to get close to the area by late Thursday. A resumption of typical fall weather then follows with stronger frontal systems favored to arrive Friday through the weekend. 12
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.AVIATION...The next upper disturbance is beginning to drop across the region, spreading isolated showers and maintaining widely variable ceilings. Generally lowering MVFR ceilings, lowering again toward 12-15z as the leading edge of the next round of precipitation approaches. This will reach the far northern terminals (KBLI toward KBVS) first, as well as across the southern tier of the area, before eventually filling in later today. This brings more widespread rain and likely lower ceilings, though confidence in either IFR or VFR periods remains generally low. Fraser outflow winds will impact KBLI Sunday night with breezy northerly winds for the Puget Sound terminals. Expect lingering precipitation Sunday night into early Monday with drying trend early Monday morning onward.
KSEA...Southerly winds at the terminal early this morning with lower MVFR stratus firmly in place and scattered showers at times. There could be some scattering of the lowest layer later this morning, with a 60% chance of improving to VFR later this morning 16-22z. Expect another lowering in ceilings with increasing showers this evening and overnight with winds becoming northerly or northeasterly at around 7-8 kt. 12
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.MARINE...Northwesterly winds will ease today over the coastal waters as a low pressure system begins to form along the southern coast of Vancouver Island. The system will then begin to move southward along the coast on Monday. Winds will turn to become northeasterly and increase late Sunday night into early Monday morning. Small Craft Advisory level winds will continue across the coastal waters through most of the day on Monday. Outflow winds will develop over the Northern Inland Waters as well as through much of the Strait of Juan de Fuca. Frequent gusts up to gale force are expected in the Strait of Georgia north of the San Juan Islands, but elsewhere SCA conditions are expected. Some gusts may meet SCA criteria through the West Strait of Juan de Fuca, but sustained winds should be lower than in the central zone and confidence is lower in the outflow winds making it all the way there. Winds will ease area-wide Monday night as the low rides down the coast into California. Broad high pressure will build in the wake of the system, allowing winds over the coastal waters to return to northwesterly and light onshore flow through the interior waters. Conditions look to remain benign through much of the week, with the next system not moving into the area until Friday.
Seas 11 to 13 ft across the coastal waters this morning will slowly ease throughout the day, becoming 8 to 10 ft tonight. Seas will remain steep with a dominant period of 10 seconds. Seas remain around 7 to 10 ft with a dominant period of 7 to 8 seconds on Monday. Seas return to 4 to 6 ft Tuesday through late week. The system on Friday may rise seas back above 10 ft.
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.SEW WATCHES/WARNINGS/ADVISORIES... WA...Wind Advisory from 8 PM this evening to 2 PM PDT Monday for Lowlands of Western Whatcom County-San Juan County.
Winter Weather Advisory from 5 AM early this morning to 5 AM PDT Monday for Cascades of Snohomish and Northern King Counties-Cascades of Whatcom and Skagit Counties.
Winter Weather Advisory from 8 AM this morning to 11 AM PDT Monday for Cascades of Pierce and Lewis Counties.
PZ...Small Craft Advisory until 5 PM PDT this afternoon for Coastal Waters From Cape Flattery To James Island Out 10 Nm- Coastal Waters From James Island To Point Grenville Out 10 Nm-Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm-Grays Harbor Bar-West Entrance U.S. Waters Strait Of Juan De Fuca.
Small Craft Advisory from 8 PM this evening to 2 PM PDT Monday for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca.
Gale Warning from 8 PM this evening to 2 PM PDT Monday for Northern Inland Waters Including The San Juan Islands.
Gale Warning until 8 AM PDT this morning for Coastal Waters From Cape Flattery To James Island 10 To 60 Nm-Coastal Waters From James Island To Point Grenville 10 To 60 Nm.
Small Craft Advisory from 8 AM this morning to 5 PM PDT Monday for Coastal Waters From Cape Flattery To James Island 10 To 60 Nm-Coastal Waters From James Island To Point Grenville 10 To 60 Nm.
Small Craft Advisory until 5 PM PDT Monday for Coastal Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm.
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NWS SEW Office Area Forecast Discussion