Strong winds down trees, power lines in foothills

Strong winds down trees, power lines in foothills »Play Video
The howling winds blew down a barn in Enumclaw overnight. (Photo by YouNews contributor lilmsleanne)
ENUMCLAW, Wash. - Strong winds gusting over 70 mph downed trees and power lines in some Cascade foothill towns Friday night, leaving thousands in the dark and temporarily blocking some roads.

Puget Sound Energy says 75,000 customers are without power on Saturday morning, mainly in south and east King County.

Seattle City Light had 3,800 people without power as of Saturday at mid-morning, mainly affecting Magnolia and east Queen Anne. Grays Harbor PUD had 900 in the dark.

The peak gust from the storm was in Enumclaw, where a weather observation station recorded a gust to 73 mph just after 4 a.m. Saturday. North Bend reported a gust to 60 mph while a spotter in Black Diamond saw a gust of 58 mph.

A High Wind Warning remains in effect for the Cascade foothills through noon Saturday for easterly winds of 30-40 mph with gusts as high as 60-65 mph. A lesser Wind Advisory is in effect for the greater Seattle-Bremerton areas until noon for gusts to 50 mph. Sea-Tac Airport reported a gust of 51 mph early Saturday morning.

The strong winds wreaked havoc with some major roadways overnight. SR-18 was closed between I-90 and the Issaquah-Hobart Road for much of pre-dawn Saturday hours due to downed trees. The roadway reopened just before 8 a.m.

In addition, Highway 169 was closed near Enumclaw by fallen trees and power lines. It was reopened at about 11:10 a.m. Saturday.

 A tree fell onto a car at South 222nd Street and 96th Place South in Kent.

In Kent, city crews have been out since 1:30 a.m. Saturday removing trees that were blown down over the road. All have now been cleared except for a large tree that is tangled in power lines on South 222nd Street, blocking access to 20 homes. Officials said it could take several hours to shut off power and remove the tree.

Strong winds were also reported in North Bend, Snoqualmie, Black Diamond and Covington. In Black Diamond, a witness reported around midnight that multiple power lines were down along 264th Avenue between 400th SE and 416th SE.

In Preston near Issaquah, crews had to close eastbound I-90 down at Jones Road due to downed power lines. It reopened a short time later.

"We have a lot of damage outside our carport canapy (sic) is on top of our car...Our boat is very likely ruined," Denise Moss Nonan of Cumberland wrote on my Facebook page. "Things are slamming my house from all sides. This is truly scary. Scarier than it has ever been."

Most towns affected are near the outflow areas of the Cascades such as North Bend, Enumclaw, Gold Bar and Cumberland, but this system also produced mountain waves that can bring strong wind gusts all along the western spine of the Cascades, even out into the eastern lowland areas like Issaquah, Black Diamond, Eatonville, and Sultan.

"Power is still on in North Bend," @Lockettlady Tweeted just after midnight. "But it sounds like we are in the middle of a hurricane."

"I think a car just hit our house. Oh wait, no, it was just one of those cows that flew in from Enumclaw," Tweeted @OuroborosSnyder.

"The (wind) just blew my thermometer off the back deck and broke it," Tweeted @SteeleThisLOL from Covington.

Another place in the warning is the far north coastal areas near the western entrance to the Strait of Juan de Fuca, such as Neah Bay, where east winds race out to sea. Tatoosh Island had gusts over 60 mph for much of the night.

Winds will calm rather quickly as we get into Saturday afternoon.

Wet snow possible around Hood Canal area Saturday and Elma/Montesano area.

Aside from the wind, showers will pick up on Saturday morning as this at low moves through. It will be all rain for 98% of the Western Washington lowlands (including all of the big cities) as the snow level will be around 1,000 feet Saturday.

Generally speaking, we're looking at rain at times Saturday as that storm comes ashore. But the western Kitsap Peninsula/ Hood Canal area could see some wet snow as those easterly winds crash into the eastern slopes of the Olympic Mountains and intense showers drag the snow levels down to the surface. It's the reverse rain shadow effect.) This is a frequent snow belt and those who live between Shelton and Chimacum are well versed in this phenomenon.

A Winter Weather Advisory is in effect from 4 a.m to 1 p.m. Saturday for the Hood Canal area and inland Grays Harbor County, including Elma and Montesano, for a much as 1-3" of snow, especially above 500 feet.

For everyone else, snow levels look to be around 1,000 feet Saturday but there is one more wrinkle that could briefly drop snow levels down to a few hundred feet or lower. (Check your elevation here.) The east winds will dry out the lower levels of the atmosphere because as that air sinks down the western slopes of the Cascades, it'll dry out the air. Now if moisture above falls into a dry layer near the surface, it can do a process called "evaporative cooling"

You can read more about evaporative cooling on our Snow FAQ but long and short of it is that the dry air can cause temporary cooling when a shower begins, and depending on how strong the shower is, it can lower the snow level a few hundred feet.

This is not a big issue for Seattle, but anyone might see the rain begin as wet snow if showers are heavy enough Saturday.

The Kitsap snow chances end Saturday afternoon, but we could see these brief 500 foot snow showers Saturday night as well. By Sunday, evaporative cooling is no longer in play and it's rain for everyone.

What causes the strong east winds?

It's yet another quirk of Washington that we can have sunny skies and yet still, the weather is dangerous in spots. During the winter, cold, dense air settles in the Eastern Washington Valley, and since the air is so heavy, it's difficult to budge, as anyone who has lived over there can attest.

But it's that density that creates very high pressure in Eastern Washington. Meanwhile, when a low pressure center approaches from the west, it creates a very large difference in pressure between Eastern and Western Washington, and the wind will shoot through the gaps in the Cascade Mountains into Western Washington to try and equalize the pressure.

To wit: During the peak of the storm early Saturday morning, Seattle's pressure was at 29.41" while Wenatchee was at 29.77".

That is why towns near the mountain passes get so windy. You're essentially standing at the end of a wind tunnel. Wind speeds decrease as the air spreads out into Western Washington and you go farther west from the mountain passes.

Mountain waves can add problems

But sometimes it's not just air coming through the mountains but over them. If the storm is strong enough, you can get "waves" of air crashing down the slopes, bringing sudden, high gusts of wind.

These occur when you have wind going across a mountain range and air flow that increases as you go higher in the atmosphere. These can create turbulent waves that act much like the water waves you see at the ocean, only it's air that’s rolling down the hills, not water.

These can bring high winds along any area near the mountains, not just next to the pass gaps. They are characterized by sudden gusts that seem higher than the sustained winds, for instance it can be blowing 20-25 mph then a mountain wave can bring a sudden burst of 50-55 mph winds.

Winds will calm down Saturday afternoon as the difference in pressure decreases rapidly.