Snow storm dumps as much as a foot in the North Sound

Snow storm dumps as much as a foot in the North Sound
There are convergence zones...and then I guess there are CONVERGENCE ZONES. We got the former yesterday morning, and the all-caps version yesterday evening.

That wacky weather pattern conspired to drop nearly a foot of snow in some Snohomish County locations Wednesday night. Meanwhile, 20 miles to the south in Seattle, the ground is completely bare you'd hardly know about all the commotion (well, except for the morning ice.)

Snow reports ranged from 5-12" across Snohomish County as the zone set up shop and dumped a steady dose of snow for several hours.

The largest snow totals are in from Maltby, Clearview, Snohomish, Echo Lake and Lake Stevens -- all close to, or at a foot of snow.

Here are some of the snow totals we've received from viewer reports. Note that these are unofficial:

Gold Bar: 9-13"
Clearview: 12"
Snohomish: 12"
East Everett Hills: 11"
Darrington: 11"
Duvall: 7-10.5"
Mill Creek: 10.5"
Lake Stevens: 9"
Monroe: 8-9"
Granite Falls: 8"
Hollywood Hill (E. Woodinville:) 7"
Silverlake: 7"
Everett: 6-8"
Maltby: 6"
Marysville: 6"
Napavine: 5"
Echo Lake: 5.5"
Mukilteo: 5"
Lynnwood: 5"
Bryant: 5"
Quilcene: 5"
Kenmore: 3-6"
Bellingham: 4.5"
Bothell: 4.5"
Langley: 4"
Mountlake Terrace: 4"
Edmonds: 4"
North Seattle (145th): 4"
Woodinville: 3.5"
Kingston: 3"
Redmond: 2.5"
Snoqualime Ridge: 2.5"
North Seattle (125th): 2"
Kirkland: 1"
Lake Sammamish: 1"

(E-mail me your snow totals -- my e-mail is linked to my byline at the top -- just be sure to measure on a flat surface away from trees or awnings. No guessing!)

Aside from the snow, temperatures dropped into the 20s for most areas, making for icy roads even in places where snow didn't fall.

That caused several school districts to close or delay start of classes Thursday morning, putting pressure on a school year that has already seen several days lost to severe weather this fall and winter.

U.S. 2 was closed for several hours by a crash that brought down power lines about 40 miles east of Everett early Thursday morning, according to the state Transportation Department.

State troopers and local police officers spent the morning responding to dozens of crashes and spinouts.

In Marysville, two teens were injured after the car they were in smashed into a telephone pole just before 6 a.m.

Witnesses said the car was going more than 70 miles per hour when it crashed near the intersection of 11th Avenue NE and NE 140th.

Firefighters had to cut the boys out of the mangled wreck and both airlifted to Harborview Medical Center in Seattle. Their current conditions are not known.

Any more snow?

The Convergence Zone is gone, but there are still a few lingering showers that are dropping random snow showers in a few spots. One shower hung out around the Bellingham area early Thursday morning and dropped 2-4" in spots up there. The Cascade foothills and Hood Canal area were also seeing a few early morning snow showers. Any of these other showers should be brief with only light snow and any additional accumulations would be under an inch.

We begin to dry out some for this afternoon, with temperatures warming into the low 40s, so we should begin the process of melting the snow that's out there.

Where do we go from here?

By the time we get to tomorrow evening, you'll wonder how in the world we got so much snow as temperatures quickly warm in advance of our next storm.

Tonight will be dry, but chilly once again. Lows will drop to around freezing.

Friday will feature much warmer temperatures as, appropriately, a much warmer storm moves in. Rain will develop by morning, and temperatures will soar to near 50 degrees. I know we had a few photos sent in of snow next to outdoor pools around here. Maybe this will be your chance to use it? :)

Rain falls Friday night and into Saturday, before tapering off to showers in the afternoon. Long range forecasts is for occasional rain next week, but temperatures well above freezing, ending any chances of snow.

Meteorological Mumbo-Jumbo

So by now, the Convergence Zone probably has about as much name recognition around here as Starbucks and Ichiro. But what exactly is a Convergence Zone?

The short answer is: it's caused when two winds collide. When the general air flow is from the northwest, as it typically is in the wake of a passing storm, that air splits around the Olympic Mountains. Some of the air goes east down the Strait of Juan de Fuca, then turns south toward Everett. The other branch curves around the southern end of the Olympic Mountains and then turns north over the I-5 corridor toward...Everett.

Those two winds collide and are forced upward. The rising air then cools, condenses, and poof, you've got clouds and precipitation. Generally the collision happens over an area between Everett Mall and Northgate Mall, but as we saw last week, that's not always the case. Last Thursday, the winds sort of weirdly collided over Skagit and Whatcom County. Other times, like the big commute disaster of last November, it can park over central King County.

(Read more in our Weather FAQ)

This snow yesterday was somewhat amusing because the convergence zone formed twice. The early morning one is what brought 1-4" between Everett and Snohomish, with Clearview and Snohomish getting nearly 4".

As that Zone fizzled, a strong individual storm cell formed over northern Kitsap County, and then really intensified as it moved across Puget Sound and into southern Snohomish County. That's what brought the heavy snow to Mukilteo and Everett -- about 2-3" in a very short burst.

In the wake of that storm, the Convergence Zone refired right where it left off, and that was the "icing on the cake" that brought the additional 2-6" that fell in the late evening and overnight hours.

So, why did this zone bring snow, despite the fact that temperatures were in the upper 30s/low 40s around the area during the day? Intense precipitation can temporarily lower snow levels.

You can read more about how this works at this link in our Weather FAQ's Northwest Snow Scenario site. This is also why these random showers outside the zone have sometimes been snow, even during the day when it was 40 or so degrees before the shower arrived.

The other factor in play was just timing. (Snow scenario 5 in our Snow Scenario page) Most of the other snow that's fallen over the past few days has just been because we were in a generally cool air mass, and our low temperatures at night dropped to near freezing just before dawn, allowing what were rain showers during the day to be snow showers at night.

As we mentioned, the weather flips around starting Friday, as we climb a good 10 degrees and no scenario will make it snow around here when it's in the low 50s :)