January 09, 2024

Will Heavy Lowland Snow Fall over Western Washington on Friday or Saturday?

Update Tonight On the Arctic Air Entering Our Region and Localized Areas of Snow

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The buzz is up regarding the potential for a major snow event over the lowlands of western Washington and Oregon on Friday or Saturday.

I have had nearly two dozen emails about this issue today and calls from local media....so folks know about the potential.

This is a very challenging situation with relatively low predictability and large differences in model forecasts.  But slowly, the picture is getting clearer...and I will tell you about it in this blog.

Our confidence in the forecast should improve substantially tomorrow and Thursday as we get closer to the event and more powerful forecasting tools (large high-resolution ensembles of many forecasts) become available.

To show you what some of the excitement has been about, here is the forecast 48-h snowfall ending at 10 AM Sunday from the main U.S. model, the GFS (started at 4 PM yesterday).  

Wow.  Roughly TEN INCHES around Seattle.  And this snow would have started to move in during Friday evening.  Ten inches of snow is like the apocalypse in this region.


No wonder folks were getting excited.

The trouble was that other models, such as the generally more accurate European Center model, were going for very little snow over Puget Sound for the same period, but predicted snow in the Portland area (see below).



Several other major forecast models did the same (took the snow south).   Another important fact was even the U.S. GFS model, run many times in an ensemble, had several forecasts with little snow in Seattle.

With all this disagreement, and thus uncertainty, I held off predicting a big snow event on Friday and early Saturday.   Some folks, including a well-known local weather video purveyor, suggested I was being "conservative", while another comment suggested I had somehow lost interest in making the hard calls.  Hyping snow events may be good for getting clicks but bad science and leads to "cry wolf" reactions.

The truth is that all forecasts have uncertainty and some are more uncertain than others.

The snow forecasts varied because different forecast systems predicted different locations and intensities for a small-scale low/trough of low pressure reaching our coast.   

 The U.S. GFS model predicted the low to be considerably farther north than the EC model, which brought the precipitation (snow northward)in the GFS model.... see below.  Both had temperatures cold enough to snow over Puget Sound.





Since the EC model is generally more skillful, the smart bet was on little snow north of Tacoma on Friday and early Saturday.   And in the latest forecast (just released), the U.S. GFS has started to drift toward the European Center solution, reducing the snow over Seattle but increasing snow over the Rose City.

Assuming that the true situation will trend towards the European Center solution, here are the latest 24-h snow totals ending Saturday morning at 4 AM and Sunday morning at 4 AM from the EC model.  Little snow around Seattle, but lots in Portland.



I will update more tomorrow and Thursday.




17 comments:

  1. It's pathetic that the GFS model is even being considered as a possible outcome when the European model is right nine times out of ten. Get ride of the dam gfs for good.

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    Replies
    1. But remember, GFS was pounded out by some of our very best hackers. And besides, it's already been paid for.

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  2. Nice blog Cliff. We concur on the importance of communicating uncertainty instead of making wild calls. Emergency managers need to be getting prepared and the public needs to know something significant is possible, but it could easily go south (literally). Here's the latest Euro ensemble mean snow depth by Sunday evening. Very little in Seattle. The control basically doesn't have any, but some of the latest Euro ensembles members are going for snow in Seattle beyond the weekend.
    https://weather.us/model-charts/euro/washington/snow-height-avg-in/20240115-0600z.html (not sure if the ensembles work for non-subscription users)

    As we discussed, the Euro is holding on to the cold temperatures.
    https://weather.us/model-charts/euro/washington/temperature-f/20240114-1500z.html
    Maybe even becoming more aggressive. Definitely the most interesting regional cold wave in quite some time, with multiple days below freezing. Getting pellets here in NE Portland as I write.

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  3. Just thought I'd post, it's snowing here in Tenino, WA, tonight! Outside temp showing 36° at ll:30pm Tuesday 1/9/24

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  4. I know you don't want or need to burn any bridges over this, Cliff. But it would be edifying and arguably very useful (in terms of serving the greater good) to name names and call out those who cried wolf with doomsday snow predictions.

    And frankly, anyone who interprets your stance as shying away from the "hard calls" is being crudely disingenuous -- or perhaps they really are that dumb. Going against the idiocracy and refusing to jump on the media whore/Snowmageddon bandwagon is the DEFINITION of making a hard call. You truly can't fix stupid, but perhaps you can at least shame it into keeping its mouth shut the next time an opportunity like this presents itself.

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  5. Keep up the good work Cliff, appreciate your honesty.
    24hrs is fine for forecasting.

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  6. Lived here for over 20 years now and I hate that our weather is so weird and unpredictable. The only thing we can ever count on is that winter will be dark and grey -- anything else is a crapshoot. Everyone was getting excited 5 days ago seeing snowflakes on their weather apps and I knew the odds were against it. The Puget Sound has a lot going for it, but weather is not one of those things. It's my least favorite feature of this area.

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    Replies
    1. I tend to agree. Although I like that summer seems to be getting longer and less June Gloom. But yes, compared to the rest of the country it's boring. Not much snow, not many thunderstorms, not much winter sun, too many fires...

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  7. Snow is not a big issue for me. I've got 4 inches now.
    What does concern me is all the cold air in northern B.C. and Aberta.
    The NWS thinks I should have near 0°F for several mornings, starting with
    an introductory Thur night low of 10. Pray that air stays east of the Rockies.

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  8. In my telling, forecasters were roundly criticized by many (including the Seattle Times) in the late 80's when they forecast snow that later failed to appear. Kids were staying home from school while the adults were staying home from work, yet nary a snowflake fell. The criticism ended after the Monster Storm of Winter 89/'90, that seemingly came out of nowhere and left people stranded at work and on the road. Then it was "Why didn't they (forecasters) warn us?"

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  9. Given the way Portland has handled anything like snow or ice in the past, I surely hope that the current forecasts are revised. The city and county are inept and ignorant about what needs to be done, both in preparation and during these events

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  10. There was a burst of heavy wet snow at around 400ft in S Bellingham this morning which whitened the grass for a short while. Looks like the next 36 hours may have a few flakes here but we will likely be a few hundred miles from the real snow over the weekend.
    That said, I guess we have all seen the models flip again as we get closer to the event so not all hope it lost!

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  11. The is completely understandable to me. I would go with the European models anyday after what we've seen in the last 10 years. The USA needs a serious update in weather computing. Good forecast, this is VERY helpful Cliff. I have bald tires.

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    Replies
    1. Hopefully you are just joking about having bald tires...super dangerous in any weather.

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  12. My big concern, personally, is Thursday night, as it will go from wet to just below freezing during a time i have plans to be out, and we live on a big hill/worry about driving on ice. Growing up in the midwest, have been in too many really dicey situations where wet roads as temp drops to and just below freezing = super dangerous sheet ice on roads. Actual snow is easier to drive in (until it's packed down into thick ice by people driving on it before can be plowed/salted as is common in the NW....). Cliff, any advice about the likelihood of icy roads on Thursday night? Thanks!

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  13. Thanks Cliff, I don't know what we'd do without you. (Swear at the constantly changing-without-explanation forecasts I guess)

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

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