November 18, 2011

Snow Update

It is is looking increasingly unlikely there will be any significant snow over the lowlands tonight north and west of Olympia.  Just a few scattered snow showers, particularly over higher hills and in a dying convergence zone near Everett and extending east.  The latest model runs show far less precipitation and a much more amorphous low center (see graphic below).  Less cold air moving fact, the freezing level has gone up to

Forecast 4 AM sea level pressure and temperatures

2000 ft, which implies a roughly 1000 ft snow-level.  Our wonderful new Langley Hill radar show some strong showers coming to the coast right now...but very little significant precipitation behind it (see below):

8:20 PM radar
The ensemble forecasting system and probcast concur on predicting dry conditions for the Sound and northwards, but some light snow showers to the southeast of the Sound. Perhaps some light snow over the NE slopes of the Olympics and eastern Vancouver Is.  Here is the predicted 24-h snowfall ending 4  PM Saturday.  There could be some light snow in the Centralia/Chehalis area and over SW Washington.   Of course, with it being  cold enough for snow tomorrow we will need to be attentive for the forecast going wrong...

Mixed clouds and sun tomorrow after the late morning, but quite cool (lower 40s should be it). Heavy rain still on tap for Tuesday.  This is a serious threat for those living near the Olympic Mountains...and will be the first major event observable with the new Langley Hill radar.


  1. What are the conditions like for snow south of Olympia. Just curious as I will be heading down to Corvalis tomorrow!

  2. Up here in North Bothell it is snowing and 34 degrees at 8:50. I am expecting temps to drop a bit in the nighttime and for it to possibly stick on the roads. Weather radar shows that we may be in a (familiar)convergence zone as the clouds and just hanging above us.

  3. My first grader, resigned to another no-snow day, after checking NOAA, KOMO, and here: "You know, Cliff Mass could be the *only* weather guy that we need. What he says is always right.* Is he the smartest weather guy on earth?"
    You have a fan! And no pressure, but the next time your site says Snow ("certified by Cliff Mass!"), there really needs to be some.

    * I explained that's not the case, and then tossed in a bit about multiple data sources and ambiguity.

  4. Hey Cliff, Sorry I left a cynical comment couple days ago but I gotta continue it tonight....

    Truth...I love the NWS...We need them. Talk about privatizing our forecasts to outside companies is idiotic...

    But i'd grade their performance around D- the last couple days.

    Winter storm warnings for Ellensburg, Yakima two days ago. Same for Spokane to the Palouse today. Now advisories south sound, eastern foothills, portland and the gorge tonight. Nothing but trace amounts across the board.

    Its like the little boy who cried wolf. After three times, we'll stop listening.

  5. There were some wet flurries around 9PM on Capitol Hill at about 400 feet elevation this evening. No accumulation. Rain showers were mixing with and changing to snow here at High Point in West Seattle when I left at about 8.

  6. @smokejumper
    User sensitivity is certainly a significant issue in the field. It is very difficult to make a call as granular as advisory/no advisory when the users who are acting based on this have such a wide range in sensitivity to the conditions. There's some people/businesses that would take such a hard hit from say 1" of snow that they need to prepare for it even for just say a .05 probability of occurrence, while other users may just want to know the most probable outcome, and others that may only care if it is a virtual certainty. So it is difficult to issue a single advisory that caters to everyone, and my impression is that the NWS tends to take a "safe" route by minimizing the false negative rate/beta error, catering to those sensitive users who want to prepare for even reasonably low probability events (in this case, snowfall). By minimizing the beta error, the false positive rate/alpha error must go up. It is an interesting tradeoff and perhaps their current approach is not ideal, though I'm sure one of those sensitive users would disagree.

  7. rock! I live in Eburg and work in Seattle. You are more reliable than any other forecast out there!!!!

  8. Woke up with white yards and roofs with a little slush on the streets this morning in Olympia. The children are out on their sleds and making snowmen (or really leaf infused snowmen). It has stopped snowing and it's melting but it was nice for a walk.

  9. woke up this morning in east olympia with 2" or so of snow on the back deck. very pretty. but it is melting quickly.

  10. It's been snowing in Eburg since 7:00am or so. Still coming down at 10:00am as I write this.

  11. We got about an inch last night in Port Townsend between 7:30 and 9. Made for a fun bike ride home!

  12. I live in a particularly cold little pocket in west Olympia near Evergreen State College. Woke up to snow, still sticking on the trees, melted on the road. At 4 pm, still a few patches of snow in my yard.


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

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