February 06, 2017

Snowy Aftermath


The Northwest Weather Workshop, the big annual weather gathering in the Northwest, will take place on March 3-4, 2017 in Seattle (NOAA Sand Point Facility).   Everyone is welcome.  For more information and to register, go to https://www.atmos.washington.edu/pnww/

One more band of snow will be passing over western Washington during the next few hours, but for most of you, the majority of the snow of this event has already fallen.     Amounts so far range from 1.5 inches near the water in north Seattle to 15 inches on the higher hills of the eastern suburbs.  Many of the schools are closed (including the UW!) and there are extensive power outages from branches laden with wet/heavy snow falling on power lines.  As shown by the outage maps, about 6000 customers have lost power in Seattle, roughly 80,000 lost power in the PSE system, and several thousand in the Snohomish PUD system.

Snoqualmie Pass is closed and the cams don't suggest an early opening.

Snow amounts varied hugely.    I had the misfortune of living in one of the least snowy locations (north Seattle with 1.75 inches).   On the other hand, on the hills behind Bellevue, one location had 14 inches (see picture from Peter Benda).

Some reports were collected by the National Weather Service (see below).  A number of locations in the Sound Sound and eastern suburbs got roughly 6 inches of snow.

The snowfall yesterday heavily controlled by temperature, since the air temperatures were close to being marginal for snow.    That was why the snow was so wet in many areas, resulting in power loss.  
Being away from the water helped.  Being higher helped.  And precipitation intensity was critical. Heavy precipitation results in cooling by melting, which can drop the freezing/snow level to the surface.    Another factor last night was easterly flow that developed west of the central WA Cascades last night that warmed the temperatures a few degrees and increased the temperatures a bit (see time-height cross section of temperature and winds at Seattle to see this).

That  easterly flow, low elevation, and water influence resulted in less snow in parts of Seattle. Bummer.

Today, temperatures aloft are cold enough to snow...the issue is moisture.   Recent radar and satellite imagery(8 AM)  show a final band of precipitation coming off the Pacific (see figures)

The latest UW WRF snow forecast for the 24h ending 4 AM Tuesday shows modest snow (2-4 inches) over the mountains, NW Washington, and SW Washington, but Puget Sound get much less.  Why?

Answer:  we will be "snowshadowed" by the Olympics as westerly flow develops aloft (see forecast map at 850 hPa--around 5000 ft-- for 1 PM.  Winds are parallel to the lines.

Was this forecast a success?  Was the uncertainty information useful?  We will get feedback during the next several days.

Finally, let us note that there has been massive snows in the Northwest mountains (several feet of new snow the past several days), which is great for skiers and wonderful for water resources next summer.  And California is now being hit by massive amounts of precipitation as well, further reducing any fears of drought or water shortages there later this year.

Public Information Statement
National Weather Service Seattle WA
736 AM PST Mon Feb 6 2017

...Snowfall Reports...

Location                     Amount    Time/Date                            


...Clallam County...
6 E Joyce                    1.0 in    0925 PM 02/05                        

...Grays Harbor County...
2 SSW Montesano              3.8 in    0554 AM 02/06           

...Jefferson County...
S Brinnon                    6.0 in    0730 AM 02/06             

...King County...   
Snoqualmie Ridge             12.0 in   0530 AM 02/06
4 WNW Enumclaw               11.0 in   0554 AM 02/06      
S Bellevue                   9.5 in    0700 AM 02/06               
Renton                       8.0 in    0554 AM 02/06   
Newcastle                    8.0 in    0725 AM 02/06
Kent E Hill                  7.5 in    0700 AM 02/06                     
1 N Palmer                   7.0 in    0603 AM 02/06  
Highland Park                6.0 in    0730 AM 02/06                     
2 S Renton                   6.0 in    0603 AM 02/06                        
4 WNW Enumclaw               6.0 in    0925 PM 02/05    
Auburn/Federal Way           6.0 in    0645 AM 02/06     
West Seattle Seaview         5.0 in    0700 AM 02/06               
3 ESE Kent                   4.5 in    0554 AM 02/06   
Sunrise Heights              4.3 in    0530 AM 02/06   
Mercer Island                4.0 in    0700 AM 02/06                  
SeaTac Airport               3.7 in    0453 AM 02/06  
Magnolia - Seattle           3.5 in    0620 AM 02/06
Upper Fremont                2.0 in    0706 AM 02/06      
Greenwood                    2.0 in    0720 AM 02/06 
Ballard                      1.8 in    0700 AM 02/06
...Kitsap County...
Port Orchard                 5.5 in    0530 AM 02/06
Bremerton                    3.0 in    0620 AM 02/06
Seabeck                      2.6 in    0650 AM 02/06                     

...Lewis County...
1 S Pe Ell                   9.0 in    0652 AM 02/06                        
3 E Chehalis                 7.0 in    0603 AM 02/06                        
4 NE Toledo                  4.5 in    0603 AM 02/06                        
1 NNW Chehalis               3.0 in    0925 PM 02/05                        

...Pierce County...
Graham                       14.0 in   0530 AM 02/06
1 S South Hill               14.0 in   0603 AM 02/06                        
Bonney Lake                  13.0 in   0700 AM 02/06
5 NNW Eatonville             12.0 in   0925 PM 02/05
Frederickson                 9.0 in    0650 AM 02/06   
1 WNW Sumner                 8.1 in    0925 PM 02/05                        
3 WNW Tacoma                 7.0 in    0603 AM 02/06      
Milton                       6.0 in    0730 AM 02/06                  
1 WNW Ruston                 5.0 in    0652 AM 02/06                        
1 S South Hill               4.5 in    0925 PM 02/05                        
2 S Ruston                   4.5 in    0925 PM 02/05                        
2 S Graham                   4.2 in    0925 PM 02/05                      
Ft. Lewis                    3.0 in    0958 PM 02/05                

...Snohomish County...
Duvall                       7.5 in    0615 AM 02/06
4 NNW Sultan                 4.0 in    0554 AM 02/06
Mill Creek                   4.0 in    0625 AM 02/06   
Tulalip                      3.0 in    0730 AM 02/06
North Bothell/S Mill Creek   2.9 in    0530 AM 02/06
3 S Lake Stevens             2.2 in    0711 AM 02/06        
1 SSW Esperance              2.0 in    0603 AM 02/06         

...Skagit County...
Lake Cavanaugh               7.0 in    0704 AM 02/06                 

...Thurston County...
4 WSW Rainier                7.5 in    0554 AM 02/06                        
1 SSE Tumwater               3.0 in    0925 PM 02/05                        
2 SSW Yelm                   3.0 in    0925 PM 02/05                        

...Whatcom County...
Mount Baker                  5.5 in    0600 AM 02/06                       
4 WNW Ferndale               3.0 in    0603 AM 02/06 


  1. 4.5" so far at only 100' above sea level, Winslow, Bainbridge Island. Even right on the bayshore there's at least 3" on the ground. Changed over from rain to snow around 8pm last night.

  2. All us folks in Eastern Washington are happy for you snow-starved people on the Westside.You get to "enjoy" what we have had continuously for the last 60 days.Ironically,we were on the warm side of the trough last night:rain and a warm southerly wind.The snowpack here in Spokane is down to "only"18 inches. :)

  3. From my standpoint, I thought the overall forecast was good and I found the uncertainty information on the blog very helpful.

  4. Great forecast!!!!!! I live in Lacey and it happened as you predicted except it moved in a bit earlier than expected. We have had about 9 inches here. 6 inches still with us. I have to say that based on YOUR information yesterday I made the decision not to go to airport this morning!! THANK YOU!! I enjoy driving in the snow but not with all those loony tunes behind the wheel of their deadly weapons!

  5. Really pleased with this forecast! It was dead on for my area (First Hill). As a Texan new to Seattle, I am clueless about what to expect weather-wise. Love the blog and I always find myself here when there is a chance for a weather event. I do miss the wild thunderstorms and chance for tornadoes, though...

  6. Some of us in NE Seattle are at 3.5-4 inches now.

  7. Why didn't we get a convergence effect around N. Seattle/S. Everett? This is what a westerly flow is supposed to generate.

  8. You nailed the forecast, Cliff.

  9. Never stopped snowing in Port Angeles, even when the sun came out, still snowing. 6" and counting. Where's our blue hole?!

  10. 4" in Gig Harbor just above Sunrise beach 370' elevation. Nephew in Buckley sent photos with measured 18".

  11. The forecast for north Whatcom County was a "success" in that we anticipated snow would arrive as early as Friday. But the amount of snow forecast was nowhere near the reality. The impression was that we might get a few inches. After the initial freezing rain & sleet (Friday afternoon/evening), snowfall total in my Lynden neighborhood was well over a foot. Temps have also been quite a bit lower than predicted. So what seemed like a possible day or two with a bit of snow has instead been a multi-day event, and the effects are going to stick with us for quite a while!

  12. "Heavy precipitation results in cooling by melting, which can drop the freezing/snow level to the surface."

    Thanks for this, Cliff. I've always wondered why the snow level drops (sometimes more than 200 vertical metres below the forecast freezing level) during higher intensity precipitation events.

    That said, I have a basic understanding of thermodynamics but can't quite reconcile "cooling by melting" with the bigger weather picture.

    Could you please elaborate on this mechanism? (or make it a separate blog post?)

    Thanks as always for such an informative blog.

  13. Blue hole is where it belongs - over Sequim right now. Snow stopped hours ago but there are three inches on the ground - very heavy with a bottom layer of slush/frozen slush. 34F right now at 1:55PM

  14. Most of Portland escaped with only a dusting, if only half of the rain that fell had turned to snow it would have been a foot, maybe more.

  15. Love the percent chance of x or Y. And the most probable outcome - that was really helpful. I wonder if it will get cold enough to freeze all this water/snow tonight before it all melts away today?

  16. Be careful if you take a lovely walk in the snow: Trees and branches are still coming down, and you can even get hit pretty hard by heavy snow falling off the branches as it warms up. The City Arborist in Seattle is very busy.

  17. Hasn't stopped snowing in victoria yet, though it's so warm and melty it's not really sticking anymore.

  18. About 4" here in B'ham 80' above sea level.
    A claimed 27 degrees, a few snow flurries throughout the day, amounting to maybe 1/2" tops.
    All main roads are clear.

  19. The variation in the Tacoma area is crazy. 2 inches in the North Slope Historic District despite an elevation of nearly 400', much more in west Tacoma and Point Defiance area.

  20. Thank you Cliff for keeping us up to date on your thoughts during these types of events! I have waited along time for this type of storm. Snowed all day yesterday, heavily last night into the morning hours. Measured a solid 11" which is the most in 24 hours I have seen in 17 years where I live in SE Auburn. Amazing how just a little elevation can make a big difference in depth with less than half of that at the bottom of my hill.

  21. What I want to know is...
    Will it still be on the ground and frozen tonight? Should we expect delays tomorrow morning? And is this it for snow in the near future?
    Happy snow day!

  22. We have 30 inches in Maple Falls in the foothills of Whatcom county!

  23. Snow shadow this afternoon was evident in Magnolia, we even got a sun break for a while.

  24. We have half an inch of slush in north Seattle! Woohoo!

  25. good forecast by you and your weather community; especially some early indications that also were not alarmist.

  26. Duvall is in King, not Snohomish, county.

  27. Hi Cliff,

    We measured 3/4 of an inch total on the outdoor deck rail as of Monday morning 1 mile SW of Point No Point in Hansville and it all melted by by 3 pm Monday afternoon. A very quick snow day for the kids.

  28. Nicely done! Proffesor Mass was ahead of the storm, gave probable outcomes and then concluded with a follow up on what occured. This why so many people follow this blog.

  29. The models were spot on in Bellingham. Around 3 inches have fallen today, on top of the 2-3 inches we got last night. Still coming down lightly.

  30. In Metro Vancouver and the Fraser Valley snow depths vary between 25 cm (10 inches) in the western areas to over 85 cm (31 inches!) in Chilliwack!

  31. There is between 10 inches in western Metro Vancouver to nearly 35 inches in Chilliwack and the Fraser Valley on the ground!

  32. Well, for me, the models were all fairly wrong and are still wrong today (Tuesday February 7). After all, it hasn't been the temperature forecast by the NWS in days. They got it wrong Friday for Whatcom and have been getting it fairly wrong (until yesterday). And now again today, they have a "short range forecast" as an alert which just notes that it is still cold. Duh. Enviro Canada is not sure when we will warm up exactly and have been predicting possible snow tomorrow for Lower BC for over 24 hours. NWS changed their forecast just recently along with telling us it is still cold. Overall, I have had to turn to BC to have a clue as to the weather we will be getting - heck NWS won't change the forecast when we are hours into it and clearly their forecast is wrong.

    I get that the models can be wack when the Fraser Flow is happening up here, but it has been messing up their forecasts since Friday now, and while BC is acknowledging it's potential effects on the forecast early on - NWS does not. Same thing happened for days with that pre-Christmas snow event.

  33. check out the run off in California https://cdec.water.ca.gov/cgi-progs/reservoirs/RES. Inflow to Shasta is almost 71KAF. The Feather is running at 49KAF and the american at 28KAF. By way of comparison, the total flow of the Columbia River in a low flow year is 120KAF.

    The Yolo bypass is flooded again. Many gauges in the Sacramento valley showing concern or flood. Marin County is flooded again. The only place, mysteriously, that does not show lots of water is the Trinity river. Trinity lake still only 62% full - where as most of the other major reservoirs show 80% - and are dumping water at high rates.

  34. 9:30a Wed 2/8 - been snowing in south Bellevue hills since about 8a this morning although nothing sticking to roads (yet)

  35. Currently snowing hard west of Hood Canal with an inch in the last hour..

    On top of the 8" from Monday.

  36. Winter storm warning effect & state of emergency declared up here in Whatcom County.

  37. Still 33F and wind from the north at the Bellingham airport at 10:25 and the hourly forecast is for 40F at 11 am. Shows how bad the forecasting is.


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