Cliff Mass Weather Blog: Is it Loss to Blow Over the Lowlands?

Several of you get asked the voltage for cold and snow this weekend, and this morn the National Weather Service put out a particular statement regarding the hypothesis of a switch to more winter-like conditions.And today, I got several calls from the media about it.And yes, the local TV stations are already talk about it online and on air.It is never just to get excited about snow too early-there are a few ways to get snow in the lowlands and so many ways for it to go wrong.

nyway, we are now near enough to the weekend, and the models are in just enough agreement, and I am comfortable talking about what I see happening.Bottom line:forget lowland snow this weekend but much of c in the mountains this week.Strong NE winds will float through the Fraser Valley into Bellingham and NW Washington and colder air will unfold over the area on Sun and Monday.Clear show of the classic La Nina pattern.Maybe snow on late Monday or Tuesday, but too early to be sure.At this point, the Mayor can preserve his snowplows in the garage and Jim Forman of KING TV can get his famous parka dry cleaned this weekend.And thither will be lots of active and interesting weather during the following week!But lets begin with tonight.A low pressure center is now passing north and northeast of us, bring a strong N-S pressure difference and gusty winds (see image). During the past hours winds have gusted to 30-40 mph over the area, with some minor damage.Nothing peculiar in November.Perhaps more limited are the stronger (30-65 mph gusts) winds predicted for tonight and tomorrow morning over the eastern slopes of the Cascades.My lights are flickering right now and my Uninteruptable Power Supply (UPS) is passing on and off!But the weather fun is only beginning!During the following two years the upper level pattern is passing to change radically-to one reminiscent of many La Nina winters-one with a really high amplitude ridge over the eastern Pacific and troughing and cold air in our area.Here is the situation on Wednesday morning aloft.Huge N-S ridge extending to the Aleutians and a high-amplitude trough to its east.At the surface, there is a strong low center NW of the tip of Vancouver Island and Very cold air move south into northern BC.On Wednesday and Thursday trough and low slowly slip southward.And a strong,cool, moist flow hits the Cascades and Olympics.the result?Several FEET of new snow at head level and above (see one 24-h period below ending 5 AM Thursday).Good for Thanksgiving skiing!But then the weekend. The low slowly weakens and moves south.No cold air over us on Saturday.On Sunday at 4 AM the surface pressure pattern and low-level temperatures (shaded) and winds (the barbs) are shown below.The stale air is still mainly stuck in British Columbia-with one exception-air starts flowing through the Fraser River Valley into Bellingham and NW Washington, accompanied by strong NE winds (see figure)The job for snow lendeds is that the precipitation over the weekend falls as rain over the lowlands since the air is too warm. And so when cold air moves in late on Sunday , things have dried out.Here is the predicted snow for the 24-h ending 4 AM on Monday.The only c is over far NW Washington and southern BC.The site changes on Monday and Tuesday, but that is too far out to be certain about anything.The frigid air will be in space and showers could bring snow in a convergence zone or other feature. And the upper level pattern looks much more care the canonical snow pattern.So keep tuned.And see that there is even some uncertainty for the forecasts overthe weekend.we are still days out and a small shift in positions ofsome features could get a substantial impact.By the way, there was a lot I didn't mention.like strong SE winds over NW Washingtonon Wednesday and Friday.and the strong coastal winds with the low on Friday.Or the strong westerly wind surge into the Sound of Juan de Fuca tonight. My colleagues at the National Weather Service will be worn down when this week of dynamic weather is done!