December 02, 2013

Nowcast: No Snow Problems for Evening Commute or Seahawks Game

I have gotten a number of emails from folks worrying about snow during the commute and after the Seahawk's game in Seattle tonight.

There will be no problems during the commute tonight and I don't think driving home from the game will be much of an issue.  But don't be surprised if some snow flurries/dusting occurs around 9-10 PM or so.

Right now (4:45 PM), the SnowWatch web site shows that air temps around 40 and the road temps are in the mid-40s (see graphic)

Cold air has just started to push out of the Fraser Gap into Bellingham, where snow began at 4:42 PM.  It is very light and will take 4-5 hrs to reach Seattle.  The latest radar shows two major local bands of precipitation over the lowlands: a convergence zone band over Snohomish County and northern King County and a band south of Bellingham associated with the Fraser River outflow.  The latter band will move south in time.  It may rev up when it interacts with the convergence zone band, which should weaken in time.    Anyway, there should be a line of weak convective showers leading the northerlies that pushes southward into Puget Sound during the middle evening.

According to the Snowwatch temperature information, the freezing level was at around 2000 ft at 4 PM.   The snow level is about 1000 ft below that.  The air is cooling, so the snow level will probably get to around 500 ft by 10 PM.   So near sea level I would expect the precipitation to start as rain as the band comes through.  Over time, melting and evaporation could help bring some flakes to near sea level, but road surfaces will be warm.   And the snow will move through quickly.

Bottom line:  no real threat at sea level even if the worst scenario occurs.  So enjoy shopping or going to the Seahawks game...the weather won't stop you....

PS:  There are more chances of snow in our future!


Are you in venture capital/private equity and have an office in the Bay Area, or knows someone who does?
If so, I have a question for you. Please send me an email (cmass at ....thanks, cliff


  1. Cliff,

    I have about an inch of graupel and slush at my house 3 miles NNE of Monroe at 400'... woke up to about 1/2" at 6:30 a.m. and the graupel came in the afternoon. For whatever reason, whenever we get snow, it seems to be intensified right in the area where I live. In 2008, we had a probably a foot more snow during the entire event compared with just a mile down the road. Might have to do with the orientation of a small ridge? Amazing how profound microclimates can be.

    I'd love to see more snow come along! Regardless, I got my exercise today scraping the icy slush off my driveway!

  2. It's so great to get a Nowcast. Thanks for the update - our household enjoys them and appreciates your work!

  3. I see some of the models calling for some form of snow next week. I'm from back east and would love too see a foot of snow.

  4. Stop teasing please! Please let us know soon if you think the snow in our future will be widespread &/or large amounts. And...any idea when it will warm up and turn back to rain?

  5. There was about an inch of slush on the NW corner of Mercer Island. Made for a slick bicycle ride about 6pm.

  6. thankee Prof! [pull o' forelock]

    i wish all the other weather sources would be so clear (hence trustworthy) about what is known, what is uncertain, and when certainty is likely, as your blog.

  7. Tonight's GFS for Sunday through Tuesday is enough to make me go crazy...even more moisture than the last run...

  8. Holy cow the extended GFS precip and temps for next Monday is a stunner!

  9. Thank you so much - our family and friends hang on your every word and appreciate you sharing the science behind it all!

    However, we are some of those crazy folks that really want snow! Here! Lots! Will we ever get it?

  10. before the weekend there were forecasts of rain (heavy) and snow (possible) but little if any rain OR snow hit Seattle. What happened? Why was the forecast so "off" ?

  11. *sigh*...yesterday the GFS was showing cold temps well into next week with a bunch of moisture (snow) Sunday through Tuesday. Today it is looking like the moisture is holding off until Tuesday, and by that time it'll start warming up. It was a nice dream while it lasted!

  12. The current early cold snap brings to mind one of the oddities of the NW climate: The asymmetry of the seasonal temperature curve. Whereas, the warmest weather is about July 31, the coldest, I understand, is at the beginning of January. So the warm-up takes nearly seven months, but the cool-down takes only just over five.

    Why so much difference in winter vs. summer seasonal lag? Other places I have lived, things are more symmetrical, and the peaks of heat and of cold are both about a month after the solstices.

  13. Cliff,

    Seems like we've had relatively little moisture this fall. How does this autumn compare with others recently in terms of rainfall, snow pack, etc?


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