February 07, 2021

Convergence Zone Snow Tonight and Major Lowland Snow Event Possible Later this Week

A major lowland snow event is increasingly possible starting on Thursday and Friday, but uncertainly is still substantial.  But before I get into that, let us start with the potential for light snow tonight, particularly for higher elevations north of Seattle.

The latest visible satellite image (below) show cool unstable air entering our region.  The air is being forced to rise as it hits the Cascades producing substantial snow on the upper slopes and passes.  A particularly heavy snow area is indicated by the blue arrow.

Snoqualmie Pass, located in that areas, has had heavy snow and chains are required in both directions.


A weak Puget Sound convergence zone is in place and this is going to rev up this evening (see below).  A convergence zone is when northwesterly flow off the Pacific  moves around the Olympics and converges over Puget Sound, producing clouds and precipitation.

The air above us has been cooling over time and the snow level is about 1500 ft and will drop further.

This cooling will be aided by a surge of cooler air from the Fraser River Valley of British Columbia.

The UW model forecast snowfall total through 7 PM tonight (Sunday) showz the mountain snows and that heavy band I was talking about....which is the culprit behind the troubles at Snoqualmie Pass.


The total through 10 AM tomorrow shows some light snow in north King and Snohomish counties from the convergence zone--- perhaps a few tenths of an inch to an inch-- above 500 ft.  It will melt quickly on the roads.


And there is another snow area over the northeast side of the Olympics as some of the Fraser River northeasterly flow is forced upward by the terrain.  The forecast wind gusts at 7 AM tomorrow morning shows the cold Fraser River winds pushing across Bellingham, the San Juans and then into the Olympics.


All of this is just a "warm up" for the real action.  

Our region is going to be hit by the coldest air this winter and by Thursday we won't get out of the 30s and perhaps even the 20s.   I mean cold, really cold. Windy.

And major forecast systems are now going for major lowland snow.  The latest European Center forecast has around 15 inches of total snowfall over central Puget Sound by Friday afternoon!  How much would pile up?  Perhaps half of that.

Looking at the ensembles of many forecasts, here is the snowfall  totals for all 51 members of the European Center ensemble for Seattle:  nearly all have significant snow.


The U.S. GFS model is less aggressive with snow, but has several inches over the area.  A big issue is the track of the storms coming in:  the U.S. GFS is taking the action further south, burying Portland with snow, with far less north of Olympia.  Keep tuned.

We will have the cold, the big uncertainty will be the precipitation.   I will be watching this carefully.

I have learned about writing snow blogs.... I am heading to the food store right now!   If this forecast becomes more certain, the shelves will be stripped of eggs, milk, bread or toilet paper.

25 comments:

  1. Hoping for snowmageddon, fingers crossed!

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  2. Strange...all local news outlets are basically saying dry...and NOAA says chance of snow...so from dry to 15 inches...how can anyone plan for this...

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    1. Easy: you plan for it to be 15 inches and stuck in the house. It is easier to adapt to good weather than it is to bad.

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  3. Sounds like a repeat of February 2019, even down to the day (if memory serves). Unfortunately for me, I get snowed in really quickly and can't even get down my steps when it snows even a little (somewhat disabled). I was snowed in almost that entire February. I always get groceries when I see snow forecast, so I'll be fine.

    I'm thankful that this year I have heat. I couldn't afford it in February of 2019. My beloved hubby had suddenly died and I was in terrible shape in every way. I'll have groceries delivered if I'm snowed in this year (if the roads are safe and the amount of snow allows 'normal' people to get up and down my steps, that is). I can afford it. And if the battery dies in my car, I can afford a new one.

    I feel very blessed this year, and always count on you, Cliff, for my weather news. And I love your Friday podcasts. Your podcast prepares me for the week ahead; plus, I learn a lot, which makes me happy.

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  4. This comment has been removed by the author.

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  5. To borrow a lyric from the venerable Backstreet Boys, "don't go playing games with my heart!"

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  6. What about Portland? Models seem to be suggesting significantly higher amounts there.

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  7. I just cannot believe the change in the forecast as everyone was saying we had run out of time this winter to have lowland snow. I really do not want to shovel the driveway. My back hurts just thinking about it. Any chance the snow amounts could be even worse (greater) than the current modeling?

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  8. I see you threw in their that we will only see half of that 15" tho??? Maybe we will see more than 15".

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    1. 15" of snow falling, but now snow on the ground. There's a difference between the two numbers.

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  9. February 2019 the snow was terrible. It was very VERY difficult to do my job. No power. Broken trees. Could not get out. Any help had a great deal of trouble getting in here. I see so many begging for lots of snow... just for ONE minute think about those of us who have to work outside all the time no matter what the weather. Half of that 15" would be extremely hard, 15" would be endless long hours and blocked roads, fences demolished by trees and limited access. More than that... well, just no. I never see those who think it is "pretty" (as they sit inside on their couch sipping hot chocolate) out here helping me shovel paths through the snow to the barns, struggle to keep water moving, chip at ice build ups, deal with no power (usual for any remotely heavy snow) and having to keep the little generator going on top of everything else. Heavy snow is not "pretty " in a place (most of Puget Sound) that is not built to handle it. Please keep the snow on the ski hills and not down here. What happened to the clear sunny, cold week that was supposed to happen? That would be much more preferable. I hope the snow forecast changes. Please.

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    1. That sounds tough. Horribly so. I hope it's less cold than predicted with no snow. I feel terrible for those impacted by truly horrendous weather elsewhere. I read that antifreeze was freezing in some places. Anyway, be well, stay safe and take good care.

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    2. If it does snow, well, that's just nature and you have no control over it. Do not blame those who enjoy snowfall for your ails. This far north in latitude, even with the moderating influence of the ocean, does not preclude this area from a snow risk. Heck, Arizona has tallied more snow than here so if you want ZERO risk of snow, perhaps check out Hawaii.

      Its not like anyone is cursing you specifically with demon snow on purpose. That 2019 storm cost me a week of PTO due to being snowed in but hey, lucky it was there to use. Helped the neighbors dig out and we got on with the day to day. Adapt and overcome! Seattle not handling snow events well is a Seattle problem, not a snow problem.

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  10. Am following you closely as we are supposed to get our second vaccine on Friday some ten miles south of our home in Des Moines.

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  11. Interestingly, the 'gold standard' weather.com app has absolutely zero snow in Bellingham Thursday through Sunday, but has Portland getting buried.

    I appreciate this is a tough forecasting challenge (as ever in Western Wa) but the spread between the forecasts makes it tough to plan ahead.

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  12. Cliff following you from Portland. Any thoughts for us? BTW love your podcast!

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  13. Just a reminder. Here in Bremerton school shutdowns lasted a week. A major cause was snow plowing blocking all major avenues and streets. Buses could get to school, but all the walkers would have had to walk on the roads at least part of the way. It was also pretty scary for the homeless to access their regular resources. When I lived in Manhattan what to do with the snow that was plowed was always the major and bigger problem. I could tell some funny stories about one particular failed attempt.

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  14. Just so you can all be as confused as me, check out the Feb 8 GFS and European pictures. New ball game! New GFS chart shows most snow staying south of Olympia until next Monday. New European chart looks like yesterday's GFS. Paging Dr. Mass!

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  15. Bought a brand new fluorescent lime green winter coat, lime green hat, but can't find my lime green gloves! I guess I have one or two more days to find them or suffer the cold chills. (Why don't you put your hands in pockets?) I can't, I have a bag to carry with one hand and cane in the other. I best be digging in my storage unit! :D

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Please make sure your comments are civil. Name calling and personal attacks are not appropriate.

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