It is the old story, the temperatures are marginal for snow near sea level around western Washington.
At 10 AM, some locations around Puget Sound were reporting mixed rain and snow, and some higher elevations (like Paine Field in Everett) were all snow. However, the temperatures aloft are relatively warm and the road surfaces have warmed after our relatively balmy weather. So not much is sticking. But you can see flakes on some web cams (see one near Paine Field below), with some whitening on grass.
The issue: warm temperatures above. A plot of temperature with height at 9:30 AM shows a freezing level of 1750 ft, which implies a snow level of 750 ft. Yes....the higher hills could get some accumulation, but not much near sea level.
A plot of temperatures aloft (over Seattle) in time, shows -2C air at 850 hPa (around 5000 ft). That is extremely marginal for snow, particularly when one does not have cold air in place at low levels.
The forecast pressure pattern is also not favorable, with a low center right over us and no feed of cold air from the Fraser River Valley (see forecasts of pressure and temperatures for 10 AM below).
The latest National Weather Service HRRR forecast (made every hour for 18 h) suggests some very light snow north of Seattle...and remember that is NOT snow on the ground, but what falls out of the sky. (see example of snowfall ending 11 AM)
Bottom line: if you are near sea level, you will not see much and there is very little risk of significant snow. If you are above 500 ft, you will see some very light accumulations. More over Whatcom county.
Sorry for folks wanted a white Christmas at sea level. But there is plenty of snow in the mountains.
At 10 AM, some locations around Puget Sound were reporting mixed rain and snow, and some higher elevations (like Paine Field in Everett) were all snow. However, the temperatures aloft are relatively warm and the road surfaces have warmed after our relatively balmy weather. So not much is sticking. But you can see flakes on some web cams (see one near Paine Field below), with some whitening on grass.
The issue: warm temperatures above. A plot of temperature with height at 9:30 AM shows a freezing level of 1750 ft, which implies a snow level of 750 ft. Yes....the higher hills could get some accumulation, but not much near sea level.
A plot of temperatures aloft (over Seattle) in time, shows -2C air at 850 hPa (around 5000 ft). That is extremely marginal for snow, particularly when one does not have cold air in place at low levels.
The forecast pressure pattern is also not favorable, with a low center right over us and no feed of cold air from the Fraser River Valley (see forecasts of pressure and temperatures for 10 AM below).
Sorry for folks wanted a white Christmas at sea level. But there is plenty of snow in the mountains.
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