Pacific Northwest to Experience Storm of the Season Tomorrow

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It’s been an interesting weather pattern for the past few weeks. Gone are the “plunges” of Arctic or, for the most part, even Canadian air that bring snow storms to the ski resorts of Colorado and southern ski regions like North Carolina. Since well before Christmas we’ve been witnessing an elevated storm track that’s taken storms farther north than usual, and this continues today. Storms that would normally sweep across the Plains to the Mid-Atlantic, have instead been skirting along the U.S./Canadian border. Even there, storms were moving uncharacteristically fast preventing significant snowfall accumulations. In the U.S., most of us fell into one of two camps — either, “Where’s the snow?” Or, “I can’t believe how warm it is!” A third camp was far-reaching in that it has affected so many of us for so long, “Man, is it windy, or what?”

One area however, is a camp unto itself. Unless you’re living in the Pacific Northwest, you’re probably not aware that many of these fast-moving storms moved right through that region before moving along the border to the Great Lakes and then northern New England. As we head into the middle of the week, another Pacific storm system is taking aim on Oregon, Washington and the northern California coastline. This one will likely be the strongest yet and may perhaps be the strongest this season.

A series of Pacific disturbances will move onshore over the next several days and interact with a deep pool of Arctic air resulting in a strong chance of heavy snow and mixed freezing rain — on top of what’s already been falling. Be advised that this is a classic heavy snow pattern for those coastal areas along the Pacific Northwest where the combination of shallow Arctic air interacts with Pacific moisture to produce heavy wintry weather.

Wednesday's ImpactWeather map shows the low just off the coast of Washington and Oregon. Click for larger image. Image: ImpactWeather

Snow is expected to increase in coverage and intensity over much of Oregon, Washington, northern Idaho and western Montana today and tonight, shifting east and south across northern Utah, Wyoming and central Montana on Wednesday. Even the lower elevations, including Seattle and Portland, will likely see more snow and even heavy bursts of snow over the next 24 to 48 hours as moisture continues to surge inland. Portland will see their heaviest snow later tonight through tomorrow morning where as much as 4-18 inches may accumulate before the transition to mainly rain occurs tomorrow afternoon. Seattle snow (snow, not the more typical rain) will increase in coverage and intensity tomorrow morning and continue into Thursday morning before a transition to mainly rain (back to normal!) occurs during the afternoon. Total snow accumulations in the Seattle area are forecast to average from 6-12 inches with locally higher amounts up to 15 inches or more.

By Thursday, the storm system is centered over the Panhandle of Idaho. Click for larger image. Image: ImpactWeather

In addition to the snow, local areas of freezing rain will be possible over broad regions of both Portland and Seattle before the transition to mainly rain occurs. Areas east of Portland and Seattle along the Columbia Gorge, where subfreezing air will likely remain trapped, may see heavy accumulations of freezing rain through Thursday which will result in very hazardous driving conditions. Total snow accumulations will likely be measured in feet across the higher elevations of the Pacific Northwest including the Cascades, Olympics,  Sawtooths and Bitterroot Mountains from this afternoon through Saturday.

Though a strong storm system can certainly be considered as one with only a high moisture content (and this one certainly is), a truly strong storm system will also pack a walloping punch from the wind, as well. This one has the moisture and this one indeed has the wind: sustained wind speeds of 30-40 miles per hour, with higher gusts, will accompany this storm with some higher elevations and mountain tops experiencing winds nearing 90-100 mph. This is the type of wind that can easily down trees, topple high profile vehicles and disrupt power supplies, while the significant rainfall will bring area rivers and streams to flood stage and perhaps beyond. The National Weather Service has issued High Surf Warnings and Advisories for coastal communities and beaches, along with Hurricane-force Wind Warnings that may drive offshore seas to 35 feet.

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