December 30, 2021

A New Weather Concern: The Slush Freeze

 The event last night played out similar to predicted.    For most locations in western Washington, a few inches of wet snow fell and temperatures rose just above freezing.

We have had a remarkably cold period in many ways.   It was the first time since 1998 that Seattle remained below freezing for three days in a row.  Many locations fell below daily low-temperature records.  And Vancouver, Canada at 4.5F had their coldest temperature in 50 years.

The winds and temperatures coming out of the Fraser River valley during this event were historic.

But something interesting (and threatening) could happen tonight and Friday night....a slush freeze...as cold temperatures temporarily return to the region.

Washington DOT and Seattle DOT need to be aware of it.

Good in a cup.  Not so good on our streets.
Courtesy of Frankielion

A Tale of Two Types of Streets

Seattle and most other towns have two types of streets:  major roadways in which plowing, sanding, and salting have taken place and the roads are drivable, and the back streets (often with substantial grades) that are snow/ice-covered and nearly impassable.   This SDOT picture this morning shows the situation well.    I can't drive into or out of my home.  


The Slush Freeze Problem

We started with icy/snowy back streets.  Then we added a few inches of wet snow last night, and temperatures are climbing just above freezing throughout the area.  There is even going to be some sunshine today to melt things even more.

In most weather situations, we would warm up and everything would melt out.

But not this year.    Consider the forecast temperatures from the National Weather Service's National Blend of Models, a calibrated statistical combination of a number of forecast models (see below).  Temperates dropping into the lower 20s the next few nights.


And the National Weather Service GFS model is doing the same thing and even colder, Friday and Saturday morning before we finally pull out of the icebox on Sunday.

Temperatures predicted by the NWS GFS model at Seattle, time increases to the right.  The average of many forecasts indicted by the black line.

My concern is that all of the slush is going to freeze tonight.  And then as temperatures warm near freezing Friday and Saturday afternoons, a super-slick situation will develop.  Nothing is more slippery than ice just above freezing.

Clear the Slush

Today is the day to clear the slush. 

SDOT and WA DOT should make efforts to move aggressively on the side streets, once the main roads are clear (and they pretty much are now).  Get rid of slush with plows while it is soft and melting.

You should do the same for your house or apartment.

More Snow Next Week?

Some models are going for more snow next week.  Considering the European Center ensemble of many forecasts (shown below).  In the top panel, there are 51 forecasts (y-axis) and time increases to the right.  The shading shows snow accumulation (darker blue and purple indicate more snow).  The bottom panel shows the average of all the models and the blue line indicates the value of a high-resolution European Center forecast.  

Increasing chances of snow on Monday, and the US GFS model is similar.   At this point, I would take it all with a grain of salt, but it bears watching.


For many reasons, our region is one of the most vulnerable to roadway icing.  Perhaps as a new mayor comes into office in Seattle, some discussion of increasing snow removal and road prep capabilities will be discussed.  The economic costs of an ice-impeded city and region are huge and more resources would be an excellent investment both economically and in saving lives.




68 comments:

  1. Just as forecast? The National Weather Service has done a terrible job of forecasting this event. The forecast was for 1 to 3 inches last weekend my Sea Tac house got 5", the forecast was for a 30-40% chance of flurries no accumulation Tuesday night and I got .5", the forecast was for 1 inch last night and I got 4.5". I had 5" of snow on the ground after the first storm, it settled to 3" and after last nights storm I have 7" on the ground. My street never thawed it was an ice sheet this entire week and I've had to walk 1.5 mile to a light rail station to get to work and walk 2 miles to get groceries twice this is not the minor accumulation the National Weather Service was calling for.

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    1. Forecasting snow amounts isn't easy. You always take the forecast with a grain of salt.

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    2. I agree that NWS has not been the best this time. I've found that weather.com (as recommended by Cliff a few years back) has been very accurate.

      Cliff - I know you have written about the need to invest more in NWS technology. Can you speak to the criticality of this? Are there any provisions in the Infrastructure Bill to improve the NWS forecasting capabilities? I'd hate to see the US fall further behind Europe and rely on commercial companies like IBM to provide our weather forecasting.

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    3. Storm1...."1 to 3 inches" means....0 to 8. You got 5. Damn near in the middle. I'd call that a flawless forecast.

      Don't like the forecasts? Go to school and improve on their methods. Until then, be thankful. Last time I checked....most folks don't pay to view this website.

      "My street never thawed it was an ice sheet this entire week and I've had to walk 1.5 mile to a light rail station to get to work"

      Are you even remotely serious Storm1? Truly, you can't be.

      Thank you for the forecasts Cliff....many of are extremely appreciative of your efforts.

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    4. I found that weather.com was better than NOAA at the 72-hour forecast. But, when we got close to the event, both weather.com and NOAA went back and forth with the amounts and when the bulk of the snow precipitation would be, Wednesday night or Thursday. Eventually, on Wednesday morning both went for 1-3 inch of snow for some point in the next 24 hours.This is too bad since NOAA provides a point forecast while weather.com is just for overall Seattle.

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    5. Completely 100% agree.. The National Weather Service has done a horrible job predicting any of this storm.. sure wish we had more accurate forecasts.

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    6. Glass half empty, or glass half full? In contrast to the naysayers here, I am astonished by how accurate many aspects of weather forecasting have become. The timing of precip events is one of them. The Christmas Day dinner I gave at my house came with a warning -- I notified everyone a day in advance that they should be off the street by 8 pm, when the temps would likely be cold enuf for snow to stick. At 6:30pm, everyone grabbed up the leftovers and left. Perfect timing, as it turned out. And this accuracy is common. Read the predictions from NOAA, NWS, atmospheric scientists' blogs, Accuweather, etc and you can plan events in advance. 60 years ago in Seattle, the only sure thing was rain in November and sun in August.

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    7. How does 1 to 3 inches mean 0 to 8? That makes no sense at all. NWS has been completely off on timing and snowfall totals and while forecasting is much better than it used to be its still inaccurate.

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  2. We moved to the area 4-5 years ago. Our first year here was a strong snow event. There has been an event every year since, shutting the area/corridor down for close to a week at one time, sometimes more than once a season.

    Government has clearly made the decision that maintaining the equipment needed to deal with these events is more costly than having the region shut down for a week or two. Right? That's the only reason we could be dealing with such continued poor planning/decision making by elected officials.

    People can't get to work. They are missing pay, but that's not a concern for government officials because that's a problem for later that they can kick down the road for a later time.

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    1. Exactly I lost $750 this week because I could only get into work 2 days and I'd used up my sick pay in previous COVID shutdowns. My 2 wheel drive car cannot handle these icy roads. Not everyone is lucky enough to live near public transit. The cost of treating these roads would be far less than the pay I'm losing.

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    2. The city has a ton of money -- my theory is they want to push as many people as possible onto public trans when we have these snow events. Same reason they downgraded speed limits 5-10mph on all our streets last summer. The list is long of all the small things they do to squeeze people out of their cars and onto public trans.

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    3. How about buy some decent tires or chains? I've been driving around with no problems all week. If you cant afford to miss work because of snow why arent you prepared with chains?

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    4. $50 for a set of chains is way cheaper than $750 missing work!

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  3. Seattle and King County are too preoccupied with housing the drug-addicted and/or untreated schizophrenic homeless to be worried about practical matters like clearing the roads of ice.

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    1. Would you rather them die on the streets, Dan? Would that make you feel better about yourself? Wow.

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    2. So, "time2lose," how many of "them" havee YOU taken in to YOUR home? Nah, no need. Show your virtue on a weather blog, then do nothing. It's the Seattle Liberal Way.

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    3. I would rather not attract them to our area as we do by failing to police petty crime, including even felonious theft and significant hard drug trade. We can spend the entire city budget on our homeless and give them the entirety of our civic attention, but as long as we refuse to civilly commit people who are a danger to themselves or the community, we will make no progress.

      True compassion involves our society firmly resolving that no, you are not permitted to live in a tent on the sidewalk because that's where you shoot your heroin. If we took a harder line, half our vagrants would move on to warmer climes and perhaps we could focus on providing civic services to actual taxpayers.

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    4. @Placeholder: Whataboutism, really? Go somewhere else with that nonsense.

      @Dan: These things are happening NOW. You don't get to project some dystopian world that isn't real. And since society won't be doing that anytime soon, what do you propose, then? All I see.if.you being in favor of allowing people to freeze to death because you're angry your street wasn't deiced.

      You both reek of privilege.

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    5. I'm not the least bit angry that my street wasn't deiced. I went out for supplies Tuesday in fact, though at a time when nobody else would be on the roads.

      The dystopian Seattle exists around us; it isn't a figment of my imagination. The inmates run the asylum as a result of choices we make, not to mention the radicalism of the homeless-industrial complex.

      The homeless are 10% people truly down on their luck quietly living in their car until they get back on their feet, and 90% drug abusers/people talking to the sky whom we refuse to compel into treatment. That's what's real. None of them should die, but the hotel plan is doomed to failure without behavioral enforcement.

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  4. It's no different here in Portland, despite an ice storm last February that left most of us here without power for over three days. There was also a snow squall five years earlier that shut down the entire metro area when it hit during Rush hour, yet the city refuses to learn from it's past failures. Coming from the Midwest where everyone knows what to do if any snow or ice falls onto the roadways, it's willful ignorance at best, and criminal neglect at worst.

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    1. Sounds like Democrat run cities really care about their constituents!

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    2. In fairness, the snowy states know what to do because they’ve had all of forever to live with it and adapt to it. And also, they’re landscape is much different than ours. I can’t envision the best equipped plow navigating some of the terrain around here, but luckily it only happens once or twice a year. Keep pressure on government for sure, but understand that it will take more than one season to adapt to what snowy states know by heart.

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    3. Jessica, if you've ever visited cities like Denver or Salt Lake city, you'd be well aware of the hills and mountains that surround these areas, so landscape has nothing to do with preparedness. Not..at..all.

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    4. Eric... Not sure I agree. I went to college in Gunnison, Colorado, and most of the winter, it was so cold the ice wasn't that slippery. To be fair, although we don't get a lot of practice here (except for skiers), the fact that it hovers near the freezing point does make Seattle's snow driving more challenging.

      And while Denver and Salt Lake sit next to the mountains, the cities themselves are flatter than Seattle.

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  5. Thank you Professor! Yes, just as you indicate, live up a slightly steep hill (city lanes all) and that nicely plowed and sanded street just a couple of blocks away might as well be in L.A. -sigh- (coffee beans for just two more days then the tea will start to look potable)

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  6. Stop firing state employees like those who maintain and drive snow plows just because they won't take an experimental Vax, you people get what you buy and your leftist progressive bs is destroyed your city. No sympathy.

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    1. As if a good percentage were in the military previously and had no problem with vaccines, "experimental" or not. Teachers didn't play games with this and were all still here and not AWOL.

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    2. Really? Did you push to get back into the classroom, or did you prefer to sit at home for extended periods of time and do the Zoom thing? You stayed at home in spite of research last year that clearly indicated that children rarely contracted the virus, and were not capable of passing it on to adults? How stunning, how brave, your commitment to the children is duly noted. And your comment regarding the military is particularly ignorant, coming from an alleged "teacher." Right now over 3,000 marines are being denied religious vaccine exemptions. Crack a book once in awhile.

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    3. It would be awesome if these comments wouldn't evolve into partisan politics constantly. It's a weather blog.

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    4. MacD... I agree. It's phenomenal, inexplicable, and, I think, historically unprecedented.

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  7. Most government officials I've seen on tv talking about the weather are at home and will probably find a way to stay there until retirement.

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  8. Great work Cliff!

    This whole event was overhyped by the lame-stream media as another way to get the public riled up over some fear porn. Thank you for calling out the amateurs and those left wing "weather forums" and staying steadfast in your forecast. We only had a couple inches of snow at our place, but our neighbor was paniced by some maps he saw online shared by a non professional. I hope he starts reading this blog rather than getting anxious over a TV forecast or what some 30 year old in his Mom's basement has to say.

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    1. Why are we making the weather political now?

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  9. Judging by the comments, snow is another political hot topic further dividing us.

    As a WSDOT employee: we’re doing everything we can with the staff and resources we have. Maintenance Depts at WSDOT were hard hit by the vaccine mandate. However, I think our highways are looking pretty good during this event, minus a few areas (I-90).

    The same folks that go to a comment section to rail against their DOT that their street isn’t plowed RIGHT NOW and have to walk to public transit instead most likely also support initiatives to strip transportation funding (Hi Tim Eyman!) every other year.

    I have a good heater to dry my boots from these winter walks to get groceries. You should too.

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    1. I grew up in the foothills of California's Sierra Nevada Mountains, it didn't snow often but when it did all of the streets were plowed or salted within 24 hours. Plowing the freeways and ignoring the surface streets is not normal, no city in the Midwest or New England has this approach. I realize the state is not giving WSDOT the funding and manpower they need to treat every street but clear freeways are kind of pointless when you can't get down you're block. As to walking to the train station thats not as easy as you might think when you are carrying a big bag of construction work tools. And no my street doesn't need to be plowed right now but it would be nice if it was plowed within a day or two and I didn't have to miss an entire week of work/pay. Also I do support infrastructure initiatives although $300 tabs for a 7 year old car is a bit excessive. In the past I would not have supported someone like Eyeman although in this next election I might support him because Democratic COVID restrictions have gone too far.

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    2. Please support your claim that Eyman wanted to strip funds for road maintenance and plowing. Thanks. I'll be waiting.

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    3. Thank you for all that you do! (And every other municipal employee on the clock during this terrible event).

      Some of us are enormously thankful for your efforts.

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    4. Thank you for your outstanding ability to service the community. I don't focus on the political opinions of anyone on this site.

      I read this blog and follow weather.com for one reason only. When I see the first hint of cold weather and snow, I make sure I'm as ready as possible. The same with summer heat, winds and other weather conditions.

      We're only at the beginning of winter, with the possibility of 2-3 tough months to go.

      When there's a break from this intense system to the next one, I'll prepare as much as possible.

      To me that's part of the beauty of the northwest: a Forest Gump treasure of unpredictability. I moved my hubby up here from SoCal so he could enjoy this gorgeous state, and he did, until the day he died. May he rest in peace.

      Again, thank you WSDOT employee aka Spoken.

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    5. I for one want to thank you for all the work that HAS been done. I have lived here almost 40 years and these huge snow/ ice events didn't happen very often.

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    6. You are not given enough resources to do an effective job. Similarly, when the bipartisan infrastructure bill passed, it should have included a big grant for WSDOT to repave I-5 from the SnoHo county line to Southcenter, rather than pursuing the fool's errand of polishing 50 year old concrete. No matter how hard that concrete is, it will still crack and be slicker in the rain than an asphalt overlay.

      The urban freeway will continue to be neglected even as chunks of the Ship Canal Bridge fall away because no elected officials in this area care one iota about pavement quality.

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    7. WSDOT is not responsible for your street. Your county and city are responsible.

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    8. Even though I'm from Salem, thank you for your service!


      Without yall the roads would be practically impossible in these events.

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    9. I say thanks to WSDOT, SDOT and the the Weather Service. Complainers are big babies. Learn how to drive in snow, buy and use chains (good snow tires & skill are better), walk, use public transportation, use food delivery - most of all be prepared. My Seattle street has never been plowed in 40 years, I have no problems. Snow forecasts and snow removal has improved greatly on the main streets. As for the Weather Service - I say bravo, good job! Anybody that didn't know snow and cold was coming, wasn't paying attention. Some forecasts are much more confident than others, some forecast elements ( wind, cold, snow amounts, timing) have varying confidence over time. It's a forecast - a probability. The future is uncertain.

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    10. No evidence from "Spoken." Typical Democratic government employee, making up falsehoods.

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  10. oh my, people. Surely you are joking, right, I hope?
    Entitled? Privileged?
    Do you have food to eat? a roof over your head? a job with income?
    Be thankful and have gratitude that you are so fortunate.
    I hope this comment is appropriate because the previous comments are not, especially during this extreme weather.

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  11. 12-24 inch icicles hanging from the western side of my house gutters, have started to thaw, and refreeze longer. I'm going to knock them off to stop them pulling the gutters down.

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  12. The comments here seem to have degenerated into a bunch of political jabber, not really furthering any meaningful discussion about the weather.
    Too bad, as it didn't used to be like this.

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  13. A couple of things...first, there is almost always more snow at my location than either weather.com or NWS forecasts. (Kitsap County, SE Burley Olalla Road near SR16 exit 20). Second, it didn't warm up enough here today to generate significant slush; just enough to partially melt ice patches on areas I'd shoveled earlier today.

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  14. So much for Seattle’s snow shadow.

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  15. Thanks Cliff for your advice. I immediately went out and shoveled all around the house.

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  16. Interesting, I'm seeing what looks like a puget sound effect snow band from just North of Tacoma to around Duvall right now, and it's snowing ever so lightly in Ballard right now. I'd love to hear your thoughts on that, Cliff.

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  17. Can’t wait for Cliff to tell us how the Colorado wildfires have nothing to do with climate change and make us all feel better!

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    1. It's called a forest fire 🤡. Climate change is part of a natural phenomenon. The storm track is keeping Colorado out of the storm train right now so it is dryer than normal right now while other places like northern California is wetter than normal.

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    2. It takes a special type of person to make such an inappropriate remark. People are being hurt there and hundreds of homes were lost.

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    3. Jeezus man, people are losing lives, loved ones, property, getting hurt, right now, and this is what you talk about?

      How bout you do something helpful, that will make you feel better.

      I donated 60 dollars to a shelter there. That's something helpful you can do from over 1k miles away. But what isn't helpful is this inappropriate comment.


      I hope you're happy.

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    4. What happened from a historical perspective was power lines were built on a fire landscape and when a rare wind event happened they sparked a fire on a newly constructed city.

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    5. Prescribed burns and proactive clearing of dead vegetation are known to reduce the speed and intensity of fires by diminishing the stock of combustible material, but federal and state agencies have long put a monomaniacal emphasis on suppression, rather than prevention, of fires.

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    6. "In a release Friday, Boulder County officials said Xcel Energy inspected the ignition area near Marshall Road and Colo. 93 and did not find any downed power lines. There were damaged communication lines, which investigators said could not have started the fire but likely were mistaken for power lines by witnesses.

      The cause of the fire remains under investigation."

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  18. For years.. I have watched NWS forecasts.. I have read this blog more times than I can count. It does surprise me how much difference there can be. NWS gets it right half the time. Cliff gets it right half the time.. but it is sad how there is no consistency. Cliff had a post 2 days ago saying we were going to be rain(snow) shadowed beyond no other in Seattle. But somehow I got 4-5" that night when I was being told we would get zero. I was also a bit surprised to have the convergence zone set up to have several hours of snowfall this afternoon that was never predicted.

    I've lived in other states.. and I will tell you, the forecasting from the NWS or anyone(including cliff) is extremely horrible here... Likely one of the worst in the nation TBH.. I know there are a lot of variables that other states don't deal with... but it is really really bad here.

    At the end of the day, it is what it is though and I do appreciate your weather blog which is generally quite insightful. Trying to get any information out of the NWS is a nightmare.. They generally give a discussion update once a day(ignoring the paragraph update they like to do)... where other states do it upwards of 3-4 times a day. You definitely get more info from the NWS twitter feed than the NWS site.

    It's been a fun last few days and I do enjoy the snow.. wish there was more.. Maybe one day, we can get a little more accurate.. who knows?

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    1. It's not that they're bad forecasters, it'd because we have the hardest to predict weather in the NW.

      We have lots of unpredictable things in our weather, like the rain shadow, it isn't easy to forecast with that. We have the cascades and rockies making it VERY difficult to predict cold waves. We have the ocean right next to us.

      I could go on with reasons. But my point is, cut the forecasters some slack, predicting our weather isn't easy.

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  19. 13 ¼ inches of Snow was my peak depth here in Salem, elevation 524.

    Much more than forecast and it was all with a south wind! And today when we finally got NE wind, it started raining.

    Weather can be crazy in the PNW.

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  20. I can't believe it gets so political on a weather blog, go somewhere else to comment about that. And be here to discuss weather, not whine about the other political side.


    Its cliff mass WEATHER BLOG, not how some of you think it is, cliff mass POLITICS BLOG.

    Come on guys... your better than that...

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    1. Hank, the snow has lingered on the roads for five days and counting. Cliff's post was a plea for governments to plow yesterday when temperatures rose above freezing -- a plea that was mostly ignored

      We disinvest in our roads despite paying the second highest gas tax in the nation. It is clear that politics drives this disinvestment, more specifically that our political leaders deprioritize transportation continuity. It is worth talking about *why* the roads are still nasty, and how that it's a result of choices we make, not that it's just impossible to craft effective snow removal procedures.

      There are places in the world hillier than Seattle that don't tolerate impassable roads for a week every two or three years.

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    2. I agree. So many people not following the posted rules for comments: "Please make sure your comments are civil. Name calling and personal attacks are not appropriate."

      Making personal attacks is easy. Whining is easy. And it's a total waste of time. On the other hand, science is hard. But so many rewards for understanding the scientific perspective, for learning about nature. Establishing the probability of weather events is one of them.

      Cliff shows an insane amount of patience on this blog. Practice from being a professor?

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  21. "On the sixth day of powder, my true love gave to me"....say, Cliff, I have been in the lowlands of Central Puget Sound for 40 years and can never remember six consecutive days of dry, powdered snow. Did I miss something? I was in Edmonds for 30 years and now South Whidbey. Seems to be the same convergence zone where we usually don't get cheated during lowland snow events. But dry, wafting snowfalls seem to never lead to half a foot of dry snow on the ground for multiple days. Thoughts? Also, the snow's beginning late Christmas night missed by a few hours the exact 25th anniversary hour of the Christmas 1996 snowfall, which started in Edmonds that night about 11:00.

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  22. There are far too many political references mostly because there always seems to be a need for someone to blame for all the petty grievances. Or for the large, difficult to quantify events. Well, sometimes "Sh*t Happens". There is still quite a bit of random chaos in the Universe which implies its best to prepare for, as well as accept it. In opposition to complaining about it and seeking never ending blame. The ultimate in the blame game is of course blaming the opposite of whatever political tribe of hoodlums you subscribe to. Our weather could not be a more perfect analog for how a little bit of chaos finds its way into our ordered lives. There also seems to be quite a bit of sensibility/common sense that has been lost, supplanted by an ever growing sense of entitlement and just being generally pissed off about EVERYTHING.

    As far as this snow/ice/cold? Its been nice to enjoy a bit of down time when the roads have been impassible.

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  23. Lol at the ridiculousness of our country. Vaccinations and the weather are now dictated by politics.

    Cliff - thanks for all you do. I have started hearings rumblings that warm weather may be delayed and we may see some snow Monday and Tuesday? Any traction on that (no pun intended)? Or should we expect any more snow from the long term forecasts? We keep forgetting that we aren't even into out normal period for snow...

    Thanks Again!

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

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