Historic snowstorm this week, or not
Snow in some parts of Western Washington and colder temperatures have everyone wondering what will happen with a storm that’s supposed to roll through the Puget Sound region.
Cliff Mass , a professor of atmospheric sciences at the University of Washington, is a widely-followed weather blogger. Heading into the weekend he wrote , “Taken literally, the latest model runs based on the U.S. global modeling system suggest a major lowland snowstorm.”
Earlier projections suggested the storm would hit late Wednesday into Thursday, now it seems it’ll be a Tuesday night/Wednesday morning event if it happens.
Mass explained how it’s difficult to predict the weather that far out, but his best reading of the computer forecast models was that, “Several inches of snow gets to Seattle, but the heaviest stuff is to the south, with roughly a foot in the Portland area and roughly half a foot to Olympia. The previous run had the heaviest snow over Seattle. This is all followed by snow showers and continued cold.”
Local TV meterologists echoed the uncertainty of predicting the storm, but said between eight and 12 inches of snow are possible in Seattle, depending on where the front hits. As always, the amount of snow you might see also depends on where you live. The National Weather Service in Seattle says areas north of the convergence zone have already seen some snow – on Whidbey Island, Skagit, San Juans and Kitsap County. Mount Vernon picked up between three- and five-inches of snow. Everett had a light dusting of snow yesterday, and Seattle had a mix of rain and snow.
Seattle even had enough big snow flakes to send my kids to the windows screaming, “It’s snowing!”
Hold on kids, Mass now thinks the chances of a major snowstorm are fading. Mass says, “It is clear now that the trend of several of the forecast models is to bring the low and the associated warm air farther north and to move things in earlier. Yes, we might get some light initial snow but right now it looks like it will rapidly turn to rain near sea level.” Mass does a great job of explaining why this storm is a particularly tricky one to figure out:
OK, lets talk about the potential snowstorm. The type of event is different than the recent snowstorms of the past few years, which have been associated with convergence zones or disturbances coming out of the north. The midweek event was going to be an over-running snowstorm, in which cold air was in place and an approaching major Pacific system pushes moist over over the low level cold air, resulting in snow…and potentially lots of it. A great example of such an over-running snow event occurred during the last week of December 1996. In fact, there were two of them that week. At my house there was nearly 20 inches of snow on the ground by the end.
The issue with overrunning snow events is that many are associated with low centers and associated fronts. If the low goes too far south, you stay cold and dry. (meteorologists hate that!). If it goes north of us, we are warm, wet and often windy. To get massive snow, the low needs to go south of us, close enough to give us the precipitation but far enough to keep the warmest air at bay. And the low south of us helps pull nice cold BC air into the region. When this sets up right you can get HUGE snowstorms, but everything has to be perfect.
Janelle took this photo of her winter wonderland in LaConner yesterday
A tiny bit of blue in the sky over I-90 heading east, just a few miles west of Snoqualmie Pass. Thanks for the photo Scott.