Dangerous winter storm approaches Western Washington

Dangerous winter storm approaches Western Washington »Play Video
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SEATTLE -- A dangerous winter storm is approaching Western Washington Saturday morning, bringing the potential for widespread heavy snows, damaging winds, and a significant number of power outages to a region still recovering from two winter storms earlier in the week.

Hurricane-force winds are possible for communities that nestle up against the Cascades in the eastern foothills of Snohomish, King and Pierce Counties, while farther west, several inches of snow are possible in the greater Seattle-Tacoma-Everett Metro area, and over toward the Olympic Mountains, they could be measuring new snowfall in feet.

The situation could be particularly dire along the far north coast, where you will get a combination of heavy snow and very strong winds. A rare BLIZZARD WARNING is in effect there.

Latest Update as of 8 a.m.:

The storm is still on track as anticipated. Satellite imagery shows the storm forming and strengthening as forecast, due to starting bringing increasing winds to the foothills as the morning progresses, and snow to the lowlands as we get into the late afternoon and evening. I did add some minor details to the extended forecast for what happens after this storm passes, but no changes to the short term forecasts that we posted Friday.

By the way, to give an idea of how much cold air is in place for this storm, the temperature dropped to -3 degrees in Arlington overnight, while we had unofficial reports of -2 in Lake Stevens and -1 in Sedro-Woolley.

Quick Overview

  • The foothills could see east winds of 50-70 mph, gusting to 70-90 mph Saturday morning through Sunday, with the strongest winds between 7 p.m. Saturday and 7 a.m. Sunday. A HIGH WIND WARNING is in effect here. Widespread and potentially prolonged power outages are a concern in this region, combined with below-freezing temperatures and dangerous wind chills.
  • The Seattle-Tacoma-Bellevue Metro area could see 3-8" of snow Saturday evening into Sunday. Gusty winds in the eastern parts of this region could get to 50-60 mph.
  • The Hood Canal area could see 8-24" of snow
  • Southwest Interior might get 6-12" of snow as well as a coating of ice from freezing rain
  • Everett north to border could get about 4-6", but has higher uncertainty
  • Some areas, especially south, could also get freezing rain and icing problems
  • Blizzard warnings are in effect for the far north coast and Cascades where heavy snow will combine with strong winds for whiteout conditions.
  • Blizzard warnings in effect for all Cascade passes -- could see 1-2 feet of snow combined with 75 mph wind gusts and wind chills ranging from 0 to -25.
  • Storm calms down Sunday evening

What's Happening?

Unlike the past few storms that have come from the chilly north, this storm is coming in from the west, and it looks pretty wet -- and much warmer than we've seen lately. So we have a much greater moisture source.

In the meantime, we'll not only have some arctic air here in Western Washington, but even more in Eastern Washington, where temperatures have been in the single digits and teens for several days. That air is very dense, and thus has higher pressure.

First, The Wind

As the strong low pressure of the storm approaches, we will have a massive difference in pressure between Eastern Washington and Western Washington. The Cascade Mountains block the wind from blowing across much of the region, but the gaps in the Cascades act like a hole in balloon, allowing air to race through into western Washington to try and equalize the lower pressure approaching offshore.

That means starting Saturday morning, a roaring east wind for those who live on the western end of those gaps. Cities here include North Bend, Gold Bar, Sultan, Enumclaw, Cumberland, Maple Valley, Black Diamond, Covington and Snoqualmie Ridge. The east Renton and Kent Highlands are also in danger of getting some of these higher gusts. If you've lived out there for any period of time, you know if you get the east wind. A HIGH WIND WARNING is in effect from Saturday morning through Sunday evening for this area.

How strong? Forecasting models as of Friday morning indicate sustained winds could be as strong as 50-70 mph with gusts of 70-90 mph. That would be hurricane force. Again, this is starting Saturday morning, but could last into Sunday. If this verifies, it would be the strongest one since December 2003.

During that storm, power was knocked out to thousands for several days. People here need to be prepared for a prolonged power outage and, with temperatures still in the 20s, dangerously low wind chills to near zero, especially if you lose power. With a severe snow event expected to occur in the lowlands late Saturday into Sunday, travel may be difficult to get to areas that do still have power farther west.

But you also need to be aware of the dangers of some alternate heating sources. We've seen carbon monoxide kill several people in the region during prolonged power outages as people use gas grills indoors, or run their car in their garage for heat. All of those can put out carbon monoxide, which can be deadly.

The highest winds look localized to the cities immediately along the Cascade foothills, however the winds will funnel out into parts of the lowlands, where winds could gust into the 40-55 mph range, especially along the I-405 and SR 167 corridors south from Bellevue south. This area of potentially damaging winds, but not hurricane force winds, would include Woodinville, Redmond, Bellevue, Renton and Auburn. We are not expecting winds of 70-90 mph in Bellevue proper or any city along the I-405-SR167 corridor. These would be in the 40-55 mph gusts.

Lower wind speeds, but still gusty, are expected along the I-5 corridor between Seattle and Fife. Note that areas north of Seattle and western Pierce and Thurston County would not be expecting problematic winds.

Think of it as just big fans sitting up in the outflow of the Cascades -- such as near I-90, SR 410 and US 2 -- turned on full blast. As you get farther away from the fan, or move north or south of the direct flow, you won't feel the wind as much.

On the other hand we could also see strong east-southeast winds along the northwestern tip of the Olympic Peninsula as the air rushes out to sea via the Strait of Juan de Fuca (Clallam Bay, Sekiu, Forks. This is covered in the Blizzard Warning.) Gusts could reach 40-60 mph here.

It'll also be quite breezy in the Admiralty Inlet, western Whatcom County and along the central coast, but wind speeds will stay in the 30-40 mph range at most. Wind would taper off all areas as the front passes on Sunday.

Next, The Snow

Overview:

  • Blizzard Warning for North Coast / Western Strait of Juan de Fuca (Clallam Bay, Sekiu, Neah Bay, Forks).
  • Winter Storm Warning everywhere else *except* Cascade foothills and Port Angeles to Port Townsend areas along US 101.
  • Blizzard warnings in effect for all Cascade passes -- could see 1-2 feet of snow combined with 75 mph wind gusts and wind chills ranging from 0 to -25.

While the strong wind is only for parts of the region, the snow will be much more widespread. As that storm arrives Saturday evening or perhaps into Sunday night, all that moisture will fall into the cold, arctic air in place, making for a heavy snow overnight Saturday into Sunday across a large swath of the region.

Some areas will get a combination of these strong winds and heavy snow. We then may undergo a transition into freezing rain or sleet or even just rain as we get into Sunday.

Specifics:

A BLIZZARD WARNING is now in effect from 4 p.m. Saturday to 4 p.m. Sunday for the North Coast / Western Strait of Juan de Fuca (Clallam Bay, Sekiu, Neah Bay, Forks). Here, we'll get a combination of winds gusting as high as 40-60 mph combined with snow totals between 9-15 inches.

This will create whiteout conditions and snow drifts feet high. Travel -- or just even being outdoors -- is strongly discouraged during this time frame as you could become disoriented. Wind chills will drop to around 10 degrees.

A WINTER STORM WARNING is in effect for most of the rest of the Western Washington lowlands, including the Seattle metro corridor. Snow will begin around sunset Saturday and fall heavily through Saturday night and into Sunday morning before tapering off midday Sunday.

But this storm's effects will be highly variable -- even more than Thursday, so it presents a hefty challenge to try and get too specific, but here is our best forecast for now:

As of now, forecasting models suggest the brunt of the storm will head into northern Oregon and southwestern Washington. Areas south of Olympia could see as much as 6-12" of snow with this storm before changing to rain or freezing rain.

The greatest snow totals will be along the western Kitsap Peninsula/Hood Canal area and the Highway 101 corridor between Shelton and Quilcene along the eastern slopes of the Olympic Mountains. The strong east winds blowing out of the Cascades will run into the mountains, where the moisture will be wrung out in a heavy, relentless snow.

These areas could see 12-24" of snow, possibly even higher amounts in isolated spots. This is on top of the snow that's still on the ground over there. Even out toward Bremerton and Bainbridge Island, snow totals could be 8-10". Residents here need to prepare for incredible snow.

On the other hand, over where the winds are roaring out east in the foothills, snow totals will be considerably less due to the dry, east wind. Snow totals here could be almost nothing to 3". (This is a trade off-- the stronger the wind, the less the snow you'll get.) This area is not included in the Winter Storm Warning.

This puts the greater Seattle-Tacoma-Bellevue metro area in a transition zone between the not much snow to the east and massive totals out west. So snow totals will be highly variable. The more wind you have, the less snow you'll see, and the farther west you go should be snowier than east.

But the farther north you go would be less snowier than south. That could mean, roughly speaking, Downtown Seattle gets 4-8", while Renton and Bellevue get 2-4". Again, these are just rough guesstimates and highly dependent on the wind and the storm's track. Plus, local elevation could affect totals. Just be prepared for anywhere from 2-8" for now.

In a change from Thursday night's forecast, it appears the north end, from Everett north to Bellingham, could see a decent amount of snow as well, but this is more uncertain as it'll depend on how much moisture makes it this far north. We'll put 3-6" as a potential total here.

The sole other area not in the Winter Storm Warning is the northeastern Olympic Peninsula area between Port Angeles and Port Townsend. Here, you'll be protected from the heavy snows as well as the strong winds by the Olympic Mountains. In fact, this area, at the moment, doesn't have any advisories or warnings issued. You still might get 1-3" of snow, but we expect this to be area to get the least impact from this storm.

The Cascades and Olympics will also be hammered. A Blizzard Warning is in effect for all Cascade passes, where we're expecting 1-2 feet of snow from late Saturday through Sunday, combined with wind speeds up to 75 mph and wind chills ranging from 0 to -25 degrees. Travel is strongly discouraged and should be put off until Monday or be done early Saturday morning. It wouldn't surprise me to see the main passes shut down anyway.

Avalanche danger is also extremely high in the Cascades.

Then, The Warm Air Arrives

As I mentioned earlier, this storm is a warmer storm, so as we get through the event, late Saturday night and into Sunday, warmer air will begin to mix in and start scouring out the arctic air in place, changing the snow to perhaps a rain or sleet. However, with that frigid east wind blowing in from Eastern Washington, that could create some areas of still-freezing air near the ground -- a recipe for freezing rain.

That would be the icing on the cake (and everything else) to make this storm truly a headache, as that could cause a thick glaze of ice to form on just about everything, possibly knocking over trees and power lines due to the added weight of the ice.

Right now, freezing rain appears limited to the south coast, Southwestern Interior and perhaps as far north as Tacoma, with an outside chance of it getting into Seattle, with lesser ice the farther north you go.

This will depend on how fast and how much warm air makes it into this region, and it's a devil's choice as to which is better. A quicker transition means less snow but more freezing rain -- perhaps as much as 1/4" to 1/2" thick in the southwestern interior.

On the other hand, a slower changeover means less ice, but more snow.

A worst case scenario is a widespread freezing rain event on top of a several-inch snow event with winds still roaring to 40-60 mph across parts of the region -- a recipe for power outages in the midst of freezing weather, especially in the foothills and in Southwestern Washington. So use today's calm weather, maybe once we get into Friday afternoon and the roads improve, to get yourself at least prepared for the possibility.

Trying to gauge exact timelines for the interactions between these three scenarios of wind, how much snow will fall before the changeover, and how long it'll take to change over (or in some places -- especially north -- *if* there's a changeover), is next to impossible, and these times will vary widely across the region with our complex topography likely making conditions highly variable. We could see a prolonged snow in some areas, while others get a quicker change to rain and limited snow totals.

It's also fairly likely that areas from Everett north don't ever change over and just remain snow until it tapers off.

But the bottom line: This weekend could be messy and residents face multiple weather-related challenges. We'll of course, be monitoring the situation through the weekend as small changes in the storm's track and development could require big changes to the forecast.

Quick Recap:

Saturday morning to evening: Strong winds develop in the Cascade foothills. No snow problems yet.

Saturday evening: Heavy snow develops region wide from south to north.

Saturday night: Strongest gusts in Cascade foothills, heavy snow falls regionwide.

Sunday morning: Begin transition to rain or freezing rain in the southwest, winds still roaring, but slowly tapering off.

Sunday midday: Winds taper off, Most of the area is now trending toward rain or freezing rain, but moisture supply is dwindling.

Sunday afternoon: Storm basically over. Showers linger, could be rain or snow, with showers of snow likely north of Seattle and rain/mix south.

Other areas:

If you're planning on trying to go south to Portland this weekend, you are facing similar dangerous conditions. Blizzard warnings are in effect from Saturday morning through early Monday morning in the western outflow area of the Columbia Gorge. 8-14" of snow is expected there amid winds howling to 40-50 mph.

In the main Portland/Vancouver metro area, a Winter Storm Warning is in effect from 10 a.m. Saturday through 1 p.m. Sunday for as much as 4-10 inches of snow, followed by a severe freezing rain/ice storm that could paralyze the city with frozen freeways and widespread power outages and cause significant delays at Portland's airport.

Eastern Washington will fare no better, where heavy snow will fall late Saturday through Sunday, dropping as much as 9-18" of new snow across the area.

Overall, travel across the entire Pacific Northwest will be incredibly difficult this weekend, and should be put off until Monday or Tuesday if possible.

Where do we go from here?

Forecasting models show whatever warming we get from this weekend's storm is very brief, with the jet stream quickly swinging back to a more northwesterly trajectory and bringing systems in from the cooler north (although not arctic cold -- we appear to be done with that after this weekend.)

Another weak system dropping in behind the mega storm on Monday. This one could be either rain or snow, but now we're leaning toward snow showers. However, it would be light showers and not expected to add any significant accumulations.

A series of weak systems continue to drop in from the northwest through Christmas week. These will be a tough call as to whether they are rain or snow, likely leaning more snow from Seattle north and rain/mix/snow from Seattle south, but none of the storms are significant.

But it does look like aside from maybe along the central coast, we'll have plenty of snow on the ground for Christmas, and no real prospects of a huge warm up that would melt it all away. After an 18 year wait for Seattle proper, it looks like it's finally time to have a White Christmas.