Updated Friday at 6:45 p.m.
Lowland snow: will we or won't we?
The first ingredient necessary is certainly here...it's cold! While Friday featured fantastic blue skies and sunshine, it certainly was not of the warm variety. A brisk north wind signaled the arrival of chilly air from Canada, and while afternoon highs still managed to hit the middle 40s for most of the Sound, the northerly breeze often gave us wind chill readings in the 30s.
After dark, the starry skies will help us to plunge mainly into the 20s around the region by dawn. Biting! The wind should be just enough to prevent widespread fog from forming, but we may end up with a few pockets of murkiness taking root in the wind-sheltered valleys. The fog combining with the sub-freezing temperatures will lead to freezing fog and black ice, so if you see a bank of low visibility, know that the pavement or steps within it could be slippery.
Saturday will be glorious, but like Friday, it will still be puffy-coat-worthy! Highs will remain in the low to middle 40s with a bit of a breeze. Clouds, however, will increase late in the day...a sign of incoming precipitation.
By Sunday morning, a cold rain works its way into Western Washington's lowlands. At first, the snow level will push back up to about 1,000' as warming southerly winds ride in with the front. We'll see a few inches of snow over the Cascade passes and resorts, and lower 40s will keep the precipitation falling in the liquid form for the first part of the day. However, cooler air once again starts to ride a northeasterly wind in from Canada later in the day, and another chill will push in from B.C. via the Fraser River Valley. As such, the lingering precipitation later Sunday and into Monday morning will start to turn over to wet snow in some spots. So far, the American (GFS) forecasting model is bringing light accumulations of about an inch near Hood Canal, whereas the European (ECMWF) forecasting model favors an inch or two in the Cascade foothills east of I-5 (around 400') and 2 to 3" in Whatcom County and near Bellingham. A lingering Puget Sound Convergence Zone on Monday may bring a batch of accumulating slushy snow near the King-Snohomish County line, too, even near sea level.
Tuesday is now trending drier, but models then bring another batch of precipitation in late Tuesday into Wednesday. It still looks cold enough for pockets of lowland snow by the middle of the week, too, but it's too early to be specific about most likely communities or totals.
Bottom line: yes, we'll see some lowland snow one way or another, although it doesn't look yet like it will go down as a Western Washington-wide white out. Rather, we'll most likely see widely scattered sleet and snow showers, and *pockets* with accumulation on the ground by next week.
Meteorologist Shannon O'Donnell
The KOMO4 Forecast Team
Today's Record Temperatures