Timeline: Lowland Snow, Frigid Temperatures In Store For Western Washington – KING5.com

SEATTLE — While it’s looking unlikely the Puget Sound region will have a white Christmas this year, anyone hoping for lowland snow will likely get their wish. Chances are it just won’t be here by Christmas morning.

While widespread heavy snow is not expected in western Washington on Christmas Day, the NWS said much of the lowlands could see between 1-4 inches of snow by Monday afternoon.

Some areas could see snow showers late Friday night, but minor accumulations of less than an inch are expected by Saturday morning for most.

And where there’s snow, there are also freezing temperatures. A weather system is expected to bring the coldest air of the season to the region this weekend, dropping snow levels to sea level. 

“While we will almost certainly see snow accumulations in Seattle, our main concern at this time is the cold that will envelop the region from Sunday onward,” said NWS Warning Coordination Meteorologist Reid Wolcott.

High temperatures in the lowlands are expected to struggle to reach freezing, with lows in the teens by early next week. It is possible lows could drop into the single digits.

“This is a rare event,” said Wolcott. “It’s been many years since those of us at the weather service in Seattle have seen forecast data like this, much like the heat event that we experienced earlier this year.”

Below is a forecast timeline of what to expect leading up to the holiday weekend and beyond:

Friday

Cooler air filters in on Friday, and a cold north wind will help that cool air push south through Puget Sound. The Kitsap Peninsula and around Hood Canal may have wet snow showers Friday morning.

Friday will be slightly colder and blustery, with widespread rain in the morning, tapering to scattered showers closer to the afternoon. The NWS said there is a chance for a thunderstorm along the Washington coast, bringing a threat of lightning and “small hail/graupel.”

High temperatures for most lowland areas will be in the upper 30s and lower 40s.

A Winter Storm Warning is in effect for the Washington Cascades and the Olympic mountains until 10 a.m. Friday for areas above 3,000 feet. Paradise on Mount Rainier and the Mount Baker and Crystal Mountain ski areas could see additional snow accumulations of 6-8 inches by Friday morning.

Stevens and Snoqualmie passes could see 3-6 inches of additional snow by 10 a.m. Friday.

Anyone traveling across the mountain passes should check the pass reports and keep a flashlight, food, water, and other supplies in their vehicle in case of an emergency.

Snow levels will be around 1,000-1,500 feet during the day but could drop to around 200-500 feet in Whatcom County as colder air moves in. Snow levels will drop towards sea level by Saturday evening.

The NWS reported snow had begun to fall in some northern portions of Whatcom County around 8 a.m. Friday.

A wintry mix of rain and snow is possible in Whatcom County in the afternoon and evening as snow levels drop and arctic air pushes into western Washington. A brief rain/snow/graupel mix is possible across the lowlands in the heaviest showers Friday. 

Christmas Day

Another system is expected to bring more precipitation to western Washington Saturday morning. The arctic air coming in from British Columbia is expected to push snow levels to near sea level.

Widespread heavy snow is not expected on Christmas Day, but the NWS said there is a chance some areas could see accumulation in the afternoon and into the night.

Rain or a rain/snow mix early on Saturday may change to just snow later in the day, but surface temperatures are expected to be above freezing which will limit accumulations.

However, some areas could see snow accumulate.

Snow showers around the Puget Sound convergence zone may bring focused showery snowfall as rain mixes in, before switching to all snow showers by Saturday evening. Snow is expected to continue to become lighter with colder, dry air moving in.

The NWS said the best chances of lowland snow accumulation will be Saturday night through Sunday night as modified arctic air pushes into the areas.

Overnight lows Saturday into Sunday will be in the upper 20s.

Sunday into next week 

Highs on Sunday will be near or below freezing, and snow levels are expected to remain at sea level until at least Monday and possibly through the new year.

Snowfall is expected around the Puget Sound region, but accumulation will range from nothing, a trace, to up to 3-4 inches.

The NWS said the best chance for lowland snow will be Saturday night through Sunday night. Between 4 p.m. Saturday and 4 p.m. Monday, Seattle has an 80% of seeing at least 1 inch of snow, a 60% chance of at least 2 inches, and a 35% chance of 4 inches or more of snow.

Bellingham, Olympia, Aberdeen and Port Angeles have a 40-50% chance of getting 4 inches or more of snow by 4 p.m. Monday.

The NWS said snow amounts generally show between 1-4 inches of snow for most lowland areas, with “heavier amounts possible in areas of heavier banding.”

The higher amounts are expected east of I-405 into the foothills, all around Kitsap and Hood Canal, and potentially around the convergence zone. Wind will be strong enough to prevent excessive snow depth near the Canadian border but though there will be blowing, drifting snow.

High temperatures next week are expected to be in the 20s, with overnight lows in the teens. Some areas could see lows in the single digits, the NWS said.

Some precipitation may return later in the week, bringing another chance for lowland snow as cold arctic air is expected to remain in the Puget Sound region.

The National Weather Service said temperatures will stay well below average into January.