Sunday, January 12, 2020

Convergence Zone snow

There are a number of moving pieces that have been occurring during the past six hours, but the most significant was the convergence zone that set up between Lynnwood and Everett, resulting in 2-4 inches of wet snow.

And then there is the cold air (the Arctic front) that is now pushing southward, with strong flow coming out of the Fraser River Valley.  As shown by this radar image a few hours ago, there has been a band of often heavy convergence zone precipitation over the North Sound, which was stronger than the models predicted. The convergence was produced by the  confluence of air moving eastward in the Strait of Juan de Fuca and air from the southwest coming around the Olympics.


The air aloft had started cooling after around 1 PM as the low center aloft moved through, and by later in the afternoon the combination of this cooling air aloft and the cooling effects of heavy precipitation (melting and evaporation) were enough to bring wet snow down to the surface in the convergence zone.    In addition, we are now getting snow showers over NW Washington associated with the invading cold air from the north.

Seattle to Tacoma have gotten little snow so far.   If you want to see the cold air coming in, here are the observations from 8 PM.  Cold, gusty winds are blowing from the northeast out of the Fraser towards Bellingham and the San Juans.


This cold air will push southward during the next few hours.   The convergence zone in the north Sound will probably weaken during the next few hours, and snow showers will move southward over Seattle and Tacoma.  It should be over by 3 AM or so.

59 comments:

  1. Thanks for the late night update! Do you expect the snow volume in Bellevue/Seattle to be equal to what the convergence zone areas have seen? Do you expect higher snowfall at moderate elevation (500-1000 FT)?

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  2. Thanks for the update, Cliff! It's frustrating that South Kitsap gets left out of a lot of forecasts...hard to tell, but seems like this whole storm is going to give us a miss. Super disappointed. :(

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    1. No kidding. It's morning and we got a total of a light dusting here in Port Orchard, while up north Poulbo got 8.5 inches. Waaaaaa!!!!

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  3. finally, some light snow in east bellevue. only some small flakes but hey - it's snow!

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  4. I was just checking the site because we measure just shy of 5 inches near Seattle Hill Road and it keeps coming down, seems to be shaping up more than predicted

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  5. Welcome to Western Washington! Nature is a tricky mistress.

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  6. As of 10:30 PM, we have 4+” of very wet snow at an elevation of about 400 feet. Considerably less down in downtown Woodinville. Amazes me how just a couple hundred feet can make so much difference.

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  7. Thanks, Cliff! Still hearing the big THUMPs as the snow builds up and then slides off our solar panels and hits the ground here in Clearview.

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  8. 4 inches in Poulsbo, 2 in Bainbridge so far. Still coming!

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  9. Yes, it's 3:30 AM, and I think I see another inch out there, so about 3" thus far, covering the road, too. I viewed some traffic cameras online, and it's definitely the north Lynnwood/south Everett convergence zone that got hit, from what I can glean. I remember one year, I left my home and it was hailing, with ominous clouds overhead; I drove a mile down I5 towards Seattle, and the sun was blinding. I'm fascinated by our convergence zone: part of the unique beauty of our area, indeed.

    OT: I loved seeing you, Cliff, when KOMO honored Steve Pool, and your article about him, too.

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  10. This turned out to be quite a minimal event in my location in Bellingham near the airport. Maybe an inch maximum of snow with very little on the roads immediately near my house. Perhaps a bit more surprising is the predicted winds never happened with a maximum gust of 35 mph at the airport (nothing close to the 50-60 mph predicted gusts). NWS has dropped the high wind warning. So, the Fraser River outflow is weaker than originally anticipated, at least so far. It is pretty chilly here, but nowhere near record lows. There is nothing out of the ordinary here as far as winter events are concerned.

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    1. Yes, the area near Bellingham airport (BLI) is often uncharacteristic of Whatcom County. Its irritating that NWS and others rely on it (along with Blaine and Clearbrook) so heavily for area condition reports and models.

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  11. school is canceled in bellevue, and for all you that didnt get canceled or work, im sorry.

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  12. 7 inches at my house in Woodinville

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  13. Here on Sinclair Inlet not so much as a flake of snow visible (don't know what fell before 6am), did see a couple distant lightning flashes over the cascades(?). Sister at the 200 feet plus level above Kitsap Lake reports school late starts, and a couple inches of snow.

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  14. 6" at 800' here in Port Angeles. Snow has picked up again this morning.

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  15. Five inches on the deck in Indianola as of 7:30 am, right in the convergence zone.

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  16. How did that convergence zone drift so far south? Unexpected, but lovely snow, in North Kitsap.

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  17. Cliff,

    The snow covered tree tops, soft grey sky, and mirror finished bodies of water are really beautiful in the city where most of us can keep dry and warm.

    However, an Alaskan man's story of survival in subzero temperatures after his cabin burned reminds me of nature's hostile environment. This article contains the story in his own words. https://time.com/5763418/alaska-man-fire-rescue

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  18. 5 inches above Hood Canal....
    Beautiful morning

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  19. The snow is awesome (5" here in Kirkland on N. Rose Hill, and another shower is dumping more as I write this), but did we not get as much arctic air as forecast? Overall everything seems pretty wet, and the low temps for Mon-Wed on the forecasts keep going up. A few days ago they were forecasting lows in the teens, and now it's mid-upper 20s.

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  20. almost 3 inches in east bellevue, and still coming down hard. (I think we're in a random shower)

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  21. Traces at Bremerton ferry & airport and Hansvile. Narrow convergence zone in between: 6" @70' in Suquamish, 9" at 300' in Poulsbo.

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  22. I have 4.5 inches in my house on the Mill Creek line.

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  23. Glacier WA had 5.2" new, and our overnight low was 15.4 F. It's still snowing, by the way, breezy, and still just over 16 F. We're are not "alpine," elevation just 910. Mt Baker Ski reported 24" new for the 24 hours - a completely credible figure. I don't see that this event is over yet. I'm very interested in the forecast.

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  24. Up to 10" now and it's still coming down!

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  25. It seems to be bit colder than forecast at my location in NW Bellingham. The morning low was 17.7F and the THSW index overnight dropped to 4.8F.

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  26. That major snow event (potential for this wednesday/thursday) that was blogged about last thursday seems less likely. Looks like the temps didn't get anywhere near the low points they were suppose to or are now (newly) predicted to over the next couple of days (i.e. we will be hovering around 30 instead of hovering around teens and 20's).

    I do see a potential for big wind event wednesday night into thursaday that will pull in some east winds. Any new info on this storm? Looks like it may be too warm for snow at that point though. And it's rare to get heavy rain with high winds, usually it's one or the other.

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  27. I've seen some places saying chance of snow every day this week, especially tonight and Wed with highs 33 or lower until Friday. What are your thoughts on the rest of the week?

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  28. Cliff, The GFS actually was very poor during this event, on extent of cold, pressure gradient out of the north, no snow south of Seattle, epic cold forecast last week, not going to happen, many forecasters now saying this was a bust!!!! Mabey a write up on how the models were so poor, snow was very isolated, and there was not near the extent of the cold. Would love to here. A lot of twitter/Social media forecasters really overhyped this event....

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  29. I suppose my question is what happened to the arctic air that was forecast? The forecast was that this would be the coldest Seattle's been in years with high temps in the 20s. I'm in Lake Forest Park and it seems to be hovering just above freezing so that any sidewalk snow already melted.

    Of course this could be a mixed blessing if it means that the slushy sidewalk-melt will form ice patches overnight and Tuesday morning.

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  30. About an inch and a half in Arlington Heights (elev around 400 feet). Very pretty.

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  31. Why get worked up or excited about snow?

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  32. My experience from this is that you have to read NWS (NOAA, i.e., weather.gov) + weather.com + Cliff Mass blog to get an idea of what could in principle happen.

    It's snowing right now (11:30 AM) at UW and other locations in Seattle. The temperature, according to NWS, is supposed to drop to 27 F by 5 PM, and chance of snow for the day is 50%. Is it going to accumulate? And/or, are we going to have icy conditions for the evening commute? I really like NWS with their point forecasts. They seem to have been erring a bit on the pessimistic side, but at least I'm prepared for the worst case scenario.

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  33. Received about 5" in Kingston. We got the first three or so within the first hour and a half or so after onset - an amazing rate of accumulation. School's closed, and I'm working from home as my kids play out back. What could be better?

    Now, I wonder, what Wednesday-Thursday has in store for us?

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  34. MAC's location in Bham is rather different than mine in north Whatcom County. While we haven't had much snow, either, roads are an icy challenge and the wind chill was below zero this morning thanks to the unending northeaster. And per a friend, roads in the Lake Samish area are icy, while I-5 last night was a real mess. Along with the fact that schools here are closed, it's an event whether we want it to be or not.

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    1. The northern and southern part of the county are often very different. The same is true for the foothills to the east. The airport is used as a reference because there are long term data, but those numbers should not be interpreted as typical for all of the county. Things usually start changing at about Ferndale as you head north. But this is not at all unusual winter weather.

      Historically, things used to be a lot more severe. Look at the list of record lows for the Bellingham Airport. Many of these records were set in the 50's:

      https://www.wrh.noaa.gov/climate/monthdisp.php?stn=KBLI&year=2020&mon=1&wfo=sew&p=temperature

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  35. About 6 to 7 inches on the Woodinville/Redmond border down the hill from Redmond Ridge.

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  36. snow is melting in bellevue. There is still about 1 - 1/12" in grass, roads are clear.

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  37. Just as I thought. The garbage in the ocean has stalled the front. Until it's addressed including in the models they are going to continue to screw up the forecasts assuming things are like they were.

    The garbage heap is bigger now then the west coast (and still growing) which effects ocean currents causing little eddies that make water stagnant then slowly heat up as there is no movement going on to disperse it. Hence a 'blob' is formed.

    The Artic Air (and any air mass) other then higher pressure will take the path of least resistance and that is certainly not going to be over us where the garbage is in the ocean. It will go elsewhere.

    If you look at Windy.com you can see where the artic air is and it's slipping eastwards to Montana as it should. It would defy the laws of thermodynamics if it didn't.

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  38. As long as the government is not telling the truth about weather manipulation and changes since Fukushima Earthquake which had big effects on the earth we are not going to have a working model. And someone needs to take into account the island of microplastic larger then the west coast in the middle of the Pacific. It effects fluid dynamics of the entire Pacific ocean.

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  39. A little over 8" on Hollywood Hill near Woodinville (~ 400' elevation) as of 12PM.

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  40. Looks like this snow event is turning into a Dud for those of us in Tacoma: was hoping for at least a couple inches. All we got was a dusting this morning, it's 36 degrees: very anticlimactic. HOPEFULLY we get more snow this winter.

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  41. 2pm Monday, still snowing in South Lake Union.

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  42. I'm sitting on the hill above lake Washington, Houghton Neighborhood in Kirkland, where it's been snowing steadily for the past couple hours and still sending down lots of powder. No wind, and the temperature hasn't come up past 33. Forecast now says snow off and on for the next 2 days!

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  43. The major disappointment is the fumble on the Fraser outflow...I think that would have aided in more snow for more folks...forecast models did not do well with this forecast for western Washington...models fumbled the cold spell...all in all the news media hyped this for ratings and viewership...loved watching them drive around Bellingham with nothing happening...the guy in Tacoma...Keith Eldridge looked like why am I out here...zip going on...

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  44. Any updates? We’re getting some light snow and little white balls here in Fremont. Wondering if I should worry about it sticking at sunset.

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  45. At least a foot of snow in incorporated Redmond.

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  46. 8 inches in Redmond Ridge..elevation 500 ft.

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  47. South Rose Hill in Kirkland received 7 inches.

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  48. After much hysteria about the upcoming Snowmeggedon in Portland this week, looks like only a dusting in the city because the cold front won't stick around long enough. Of course, far different story in the coastal mountains and Cascades.

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  49. 9 in. in Poulsbo not near the Sound

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  50. While nowhere close to record-setting, the past 24-hr have produced some of the coldest maximum temperatures that have been measured at my location in NW Bellingham and at BLI since the January 2012 blizzard. The 24-hr maximum temperature at my location is 21.9F, at midnight Monday 1/13 and the maximum diurnal temperature is 19.9F. It will be interesting to observe tomorrow's temps as I suspect that period will be most likely to produce notably cold temperatures. For reference, during my period of record, which begins 10/1/15, the lowest temperature I've measured is 15F on several occasions and the coldest maximum daily temperature I've measured is 25F on a few occasions. The last time BLI recorded a daily maximum temp below 20F (19F) was during the January 2012 blizzard (the minimum temperature was 10F - lowest temp for that location since January 1996).

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  51. 15° in lynden, the frasier valley winds are howling. I'm expecting heavy snow here Wednesday and Thursday.

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  52. It snowed nearly all day here in Bellingham, lightly, with a few short flurries. I live in Geneva neighborhood and we are close to Lake Whatcom and always get a bit more than downtown. Just a dusting downtown, but close to 2" up here.

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  53. Any news on this moisture that is supposed to arrive Wednesday/thursday?

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