January 11, 2011

Snow Update

Will Try An Experiment Today--A 4 PM NOWCAST
At 4 PM I will do a nowcast on this blog...describe what is happening at that time and what is expected over the next few hours.

Perhaps can help you decide whether to go home early or cancel that evening event. But my real reason is that I think that the missing ingredient in forecasting today is very frequent local updates.

New runs are in. The latest high-resolution run shows light snow hitting Seattle between 5 and 6 PM and perhaps could hold out until 10 PM before it turns to rain. Could be some freezing rain at the tail end.

Here is some graphics I have never shown...model prediction of temperature and snow at 1000 ft. The red lines are snow mixing ratio at 1000 ft (related to snow intensity). The colors indicate temperature (red...too warm for snow, etc). Showing 1000 ft because it takes about that distance for snow to melt. If no snow at 1000 ft, there wont be anything at sea level. Click on them for bigger image.

Here is 5 PM. Puget Sound clear--snow coming into coast.

7 PM. Snow over Seattle and west. Much less snow east of city and south (easterly winds are bad for snow on east side)

9 PM: Still some snow from Seattle north and west. Upslope flow is giving much more snow SE of the Olympics.

Midnight...its over folks...except for the far north. RAIN and warm.

NW Washington and the Kitsap will get hit much harder than Puget Sound country. Could the timing be off an hour or so? You bet. Could the distribution be slightly different? Sure. But I bet these graphics provide the key story plots

And we can watch the winds and temperature change aloft in real-time using the Sand Point Profiler....

here is the latest plot (time on x axis, height in meters on y):Red lines are temperature and wind barbs in blue. Good easterly flow and temps just below freezing (you have to add one to these temperatures, which are in degrees centigrade for reasons I don't want to get into).
You can view this in real time at:


And check the latest weather radar imagery..you will see everything unfold. Or keep your eyes on Seattle RainWatch (will be SnowWatch tonight!):


So bottom line: if you are in Seattle and you get home by 4 PM you will have no problem. By 5-6 light snow should hit. Over by midnight, probably sooner. Tomorrow's commute will be fine.


  1. Amazing dramatic video of yesterday's flash flooding in Queensland:


  2. I have been watching the long range (10 to 15 day) forecasts for Seattle since the 1st of January. Beyond the first 36-48 hours the prognostications are rather inaccurate and seem no better than assuming average climatological data will apply. My understanding is our winter weather is largely dependent on the Aleutian Low and the meanderings of the Polar Jet. In reality, can we really predict the migration of the ridges and troughs of the Polar Jet (in winter) more than 3-4 days in advance? Is that the limiting factor in winter weather forecasts in Western Washington?

  3. Here in Bellingham, I'm still wondering about the strength of the Fraser outflow. After all, geologically speaking Bellingham sits on the edge of the Fraser Valley. Canadian forecasts are calling for below freezing temps through the night with snow accumulations of 4-6." Rain not to start until sometime Wednesday morning when the outflow is finally overwhelmed by synoptic SW flow. I'd love to see that same map from the d04 1.3km domain.

  4. Any info on the Bothell/Arlington area? I just moved here but we seem to get hit worse than Seattle when it comes to inclement weather.

  5. Cliff, I very much appreciate the time you take in your blog to explain the 'why' behind the 'what' (and more detail about the 'what' in the first place). Not only does it do those of us interested in the weather lots of good, but shows the practical side of science too. Thanks for all the hard work you do, and we all enjoy it so keep it up!

  6. Cliff,
    Thank you so much for the updates!! I live in Silverdale but work on base at Keyport and a NOWCAST would be most excellent. May allow me to jet out of here before 1645. Latest solutions this morning still seem to have around 2inches for our area.

    What's the probability of freezing rain? That's the worse! We definately need these hourly updates, and they are appreciated by all! Harrison

  7. A little more info needed for this novice, thus probably thousands of others, re the Sand Point Profiler image....what are the wavy red lines? Really enjoy reading your stuff. Keep it up.

  8. the million dollar question, where do we ski tomorrow? Stevens or Crystal?

  9. Nowcast is GREAT idea as a test. Then people can know for sure what is coming for rush hour. Also, would be nice to see coastal radar :) I know you are already on top of that. P.S. I was one of your students in atmos, graduated '96 and have always enjoyed your work. I'm in the high IT industry but weather is still a hobby, especially storms. I will say all those computer labs and courses helped me out in high tech even though I didn't end up as a forecaster.

  10. I am thrilled with this promise and the nowcasting, Cliff... thanks so much... any chance you could to a quick update at 3 pm as well? That's when I'm going to decide when to "make my run for it" -- driving to pick up the kids and then home... but we're on the Eastside so I'm refusing to "panic"...

  11. I agree that frequent, local updates are a missing ingredient in forecasting ~ emphasis on local. Trouble is, so many of us are in our own little micro-climate, and even two people within the same general area can have vastly different realities.

    Case in point, someone posted here earlier today and said: "The winter wonderland has persisted for a change up in Whatcom County. Here the thick, heavy snow still clings to all the tree branches and everything else." That's true of Bellingham and environs, but certainly not the case in north part of the county, where our conditions are often drastically different than they are down the road. It makes more sense for us to listen to forecasts specific to the Fraser Valley region.

  12. I am thinking you should take the drudgereport.com approach; klaxons, blinking red lights, and a non-flattering picture of the mayor

  13. Really like this blog - thanks for showing & explaining those graphs. Very interesting!

  14. I teach an evening class from 6 pm - 10 pm, at South Seattle CC. I drive up a hill to get there. From the above-freezing temperatures, my inexperience with how the campus is hit by weather, your comments about "less snow in the south," and the campus not yet declaring a closure for the evening, I am tempted to hold class as usual. Is that just a bad idea?
    I'd like to plan a few hours ahead so students can stay home if I cancel class.
    thanks, as always!
    Dr. Gibbons

  15. Did you mean to say NOWCAST,or did you really mean SNOWCAST??? :)

  16. dds4, the answer it whichever has better plowing. Snow reports in both places are calling for a foot or so per day with Crystal being slightly less windy. Have fun! I'm counting on semi-clear roads for our mini-van on Sunday when we head up.

  17. Very light snow flurries are starting where I live near Copalis Crossing Washington out on the coast at 2:27.

  18. The NWS map shows 1-3" for North Bend, but when I move the prediction area over to our location, about 5 miles ESE of the town, it is showing 5-9" tonight and and additional 3-7" tomorrow. This is where I get confused. Often we will get snow and the town will be dry or just rainy. There is probably a 5F+ difference between there and here. We are right in the foothills pretty well surrounded by 4000-5000 foot peaks at about 700'. About 20 minutes west of Snoqualmie Pass off I-90.

    But from what I surmise, because of the easterly flow over the Cascades, we should not be getting much snow according to your models? It's quite windy here now, some good gusts, and it hasn't even hit 30F. So this is why I never know who to believe and always prepare for the worst.

    I figure if I prepare for the worst and nothing happens, great. If a big event does happen, them I am ready. That's why I believe any information about major weather events is more than welcome and should be broadcast, even if they turn out not as bad as expected.

    Thanks for all you do, Dr. Mass!!

  19. It started snowing out here in Hoquiam about 5 minutes ago.

  20. Cliff - I'm wondering about the possibility of ice on the roads. I wiped out on black ice on my bike Sunday night, and have no desire to repeat the experience. Is there a black ice forecast?

  21. Real time weather... isn't that what twitter is for?

  22. Michael Dempster--the red lines you asked about on the Sandpoint Profiler are isotherms. The example Cliff had showed temps of
    0C to 3C. This is a very useful tool and is often used by the local air pollution control agencies to watch the inversion and such. If you visit NOAA at Sandpoint and walk along the lake, you can hear the machine screech occasionally as it does its sampling.

  23. I really appreciate the Capital Weather Gang (WA Post)blog, tweets and continual updates plus reader comments. It was great last year during the Snowmageddon storms and for me to keep an eye on condition for my parents. http://voices.washingtonpost.com/capitalweathergang/#forecast

    I live in the Yakima Valley and enjoy your blog when I am headed over the mountains


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

Is Global Warming Causing Aircraft Turbulence to Increase?

 After the turbulence encounter by a Singapore Airlines aircraft,  there has been a slew of articles claiming that severe turbulence inciden...