I have held off talking about this until we were closer in time and uncertainty had declined, but there is a very good chance that some of you living in the western Washington and western Oregon lowlands will see some flakes on Tuesday and Wednesday.
I don't want to paint this as a snowy apocalypse, but there is a significant chance for some light snow, with marginal accumulation.
It won't be this bad
Let me be VERY clear about something.
Snowfall is NOT the same as snow depth. Snow melts on the surface and gets compressed. Snow depth is generally MUCH less than snowfall.
The predicted snowfall total through Thursday morning is shown below.
The Olympics get hit hard, with much of the lowlands experiencing some flakes, including some bands of a few inches of wet flakes.
Oregon will get even more snowy bounty with lots in the mountains and some accumulation in the southern Willamette Valley:
The lower-resolution European Model is similar, but has less snow over the western Washington lowlands.
When will the snow start, and what is the uncertainty in the forecasts?
A good tool for answering these questions is ensembles of many forecasts.
The National Weather Service global model ensemble forecasts (below) for Bellingham are very generous with snow (I suspect too much). The gray lines show that the various solutions were all over the place (substantial uncertainty), with the highest resolution model indicated by blue (and the average of all the forecasts by black).
So what is going on?
As shown by the upper-level (500 hPa, about 18,000 ft) forecasts for late Monday, a strong trough of upper-level low pressure will move southward down our coast.
This is a well known as a cold pattern for our region.
As shown by the surface forecast for Wednesday morning, this will bring VERY cold air into British Columbia (purple colors, blue is cold enough to snow) and low pressure just east of Astoira.
This configuration will pull cold air from Canada into northwest WA, particularly through the Fraser River Valley.
To illustrate, below are the predicted winds and temperatures on Thursday morning. You can see the cold northwesterly flow coming out of Canada.
Give me the chills to look at it.
Hopefully, this bountiful snow will calm down some of the current panic in the media and social media about the current low snowpack.
Do you think there is a chance we can have an actually good solid snow/storm in this last half of the month? Given the below average temps and above average precipitation we’re expected to see?
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ReplyDelete"During the next few weeks, there will be substantial snow in the mountains, as shown by the predicted totals through March 2 (below)."
I'll believe it when I see it. There are two facts that need to be considered:
1) Long range forecasts (more than a week out) are notoriously unreliable.
2) Multiple times this winter we were supposed to have some big dump of snow, only to have very little. If you doubt me, you don't read the UW forecast discussion on a regular basis.
I sincerely hope I'm wrong. I hope that this particular part of winter has lots of snow, and we at least get somewhere close to normal (in the mountains). But given the pattern this winter, I fear that won't happen.
Good points. Forecasters are already backing off.
DeleteHopefully some convergence snow! Doing my snow dances!
ReplyDeleteHe's the professor You sposed to take notes and don't talk in class
ReplyDeleteMt Baker's been getting more snow than the passes farther south - quite a bit more - and the inversion conditions swapped back to 'typical' (in the 20's and 30's). It's a different convergence zone up here? The skiers have been pretty happy, despite the road damage.
ReplyDeleteWe seem to get more snow in February. It was on 2/14/2021 that we received 9” of snow. I live in the convergence zone.
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