November 25, 2010

Its Snowing

Sitting in Seattle right now, its 30F and big aggregate snow flakes are slowly drifting down outside of my window. That plus a nice cup of tea and a successful forecast--life doesn't get much better than that.

But it won't last unfortunately.

Right now a warm frontal zone is moving in overhead...that is producing the precipitation, but it is also producing warming aloft over the region. Here is the latest infrared satellite picture. You can see the main front offshore (band extending SW-NE) and the warm front is the stubby appendage extending NW-SE over us. It will only give us 3-6 hr of precipitation.
Here is the latest (6:42 AM) radar--in clear air mode, because the precipitation is light. You can see the precipitation (snow) and also an area just east of the Olympics is not getting anything. The reason--there is rainshadowing (really snowshadowing!) because the flow aloft is out of the northwest. So the folks on Kitsap with all the power outages are not getting much snow....there are balances to life evidently.
Temperatures are warming aloft. Here are the hourly temperatures soundings (temp plot in the vertical) here in Seattle from the profiler. These temperatures are really virtual temperatures (don't ask...just subtract about 1C for regular temperature, and yes they are in C). Height in meters. You are looking at plots starting at midnight (2508) to 6 AM (2514). The clear message is that temperatures are warming and we now have a layer near freezing in the lowest several hundred meters--this is a layer of precipitation melting. These are wet snowflakes.Here is a different view of the temperatures and winds above us from the profiler...called a time height cross section:You can see the warming southerly and southwesterly flow (look at the wind barbs) above us and warming is evident..yesterday above us the virtual temperature was -8C at 500 meters, now it is -1C (really -2C actual temperature). This snow is not going to last long..a few hours at most. Clearly, the warming is happening a few hours faster than expected by the models last night. So I would not give the snow much more time now...hour perhaps over Puget Sound. But it could hold in longer over NW Washington, where cooler flow exiting the gaps will maintain the snow for a few hours more.

This is good for DOTs and holiday travel around the west....temperatures are now climbing above freezing and wet snow will end in a few hours. Good for holiday travel. And the end to an early major cold snaps around here--one that will go into the record books like 1955 and 1985.


  1. We are getting enough "light snow" this time that I'll put my skis on for a quick run out the door. We are still getting nice, fine, powder snow quickly accumulating in Bellingham. I am Thankful! Happy Thanksgiving to all the weather watchers and be careful! : )

  2. Snowing moderately here on Sinclair Island right now. Have about 2 inches of new snow so far. 30 degrees. It will be a mess when it turns to rain.

  3. Thanks for your amazing and informative posts! Happy Thanksgiving!

  4. Cliff,

    Where you you get your adiabatic lapse rate charts? As a private pilot, I find this information incredibly useful, and yet I haven't been able to locate the graphical charts you have here.

  5. In Sammamish, we've had 2 inches, now followed at 10:00am by winter mix. We've piled up some snow in the backyard so our lab will still have something to play in when the rest melts. Our snow usually stays far longer than everyone elses, though. Hopefully the fact that we have a grand total of about 5-6 inches will help it remain (in the grass, not the roads).

  6. Dare I say the extended GFS has more cold air nearby in the 8-10 day range.

    I know, I know nothing to be excited about yet, but very interesting that we havent gotten the wet warm November action yet.

  7. Shouldn't it all refreeze tonight, though? I'm confused by forecasters saying that it's okay for holiday travel, but then seeing that there is a low of 26 this evening per KOMO forecast last night.

    Wouldn't the travel be terrible if there's a wintry mix which turns leftover snow and ice to slush, only to refreeze this evening while folks are traveling back from day trips?

  8. @Dana: Forget about KOMO. It'll be nearly 40 in Seattle tonight. Maybe you were watching a Pass Report?

  9. Michael said...
    "Dare I say the extended GFS has more cold air nearby in the 8-10 day range. I know, I know nothing to be excited about yet......"

    I remember a similar post about a week ago...And I remember hearing that we shouldn't get excited that far out....Hmmmmmm....wonder how this is going to play out....I don't think it's supposed to be as cold though...just low to mid 30's for highs and mid to upper 20's for lows. Sure would be fun to get more snow...but I'd like it to stick around for a while next time! Can't wait to see what the Christmas/New year time frame brings. It seems like we get some good snow around that time every year! I really hope this isn't our only lowland snow for the season!

  10. TONS of snow coming down here in Vancouver... we have about 6" on the ground and it's not really showing any signs of stopping. Environment Canada has pushed back the rain a couple of times now - first it was 10AM, then 1PM, now it's 4PM... Temperature is right around freezing though and has warmed a bit for sure!

  11. Hey! another fantastic blog. i'm a regular follower. beautifully written. im dreading the snow here in england. i remember in chicago it was crazy when i lived there.

    think you might be interested in some of my articles and blogs, feel free to have a read

    keep up the good work!

    all the way from england


  12. Dana, the temperature you see there is refering to the morning low of that specific day, so 26 was today's forecast moring low temperature. The low you see for tomorrow will be tonight's low temperature, reaching its lowest point tomorrow morning.

  13. Dana asked if it would freeze tonight, having seen a forecast low of 26--but this does not agree with the current forecast: Probcast has a low of 41 for the default zipcode of 98105, with the chace of freezing in Seattle 0%, and a 55% chance of rain.

    If I go to my neighborhood forecast, clicking on the NWS Seattle forecast map, my location (Mountake Terrace) gives a forecast low of 36 and an 80% chance of rain.

    Even if it hovered around 32, the roads would just get better--especially with all the stuff they've put on the main roads. It was the bitter cold with snow falling and wind that screwed up the roads as the Canadian air arrived the other day...whole different ballgame now with the switch to marine air and Pacific fronts again.

  14. In the last 8 hours just got my power back. We got hit so hard on Silverdale Ridge. Gusts close to 65. Blizzard conditions on Monday night. Unreal. Took six hours to get from Kingston to Silverdale on Monday evening. Thank goodness for 4-wheel drive.

  15. In the last 8 hours just got my power back. We got hit so hard on Silverdale Ridge. Gusts close to 65. Blizzard conditions on Monday night. Unreal. Took six hours to get from Kingston to Silverdale on Monday evening. Thank goodness for 4-wheel drive.

  16. Special blue, a ski wax for fresh snow up to 0 degrees C. 7" of snow now at the UBC golf course (Point Grey, Vancouver) but its already above 1C. No rain yet.

  17. Up in Bellingham, we got another good inch of snow before the warm front finally arrived around 3PM or so. Right now the roads are just slusly.

    We may be done with the snow now, but this is only Wave One of La Nina. Prepare for the worst to come yet.

  18. NWS is predicting snow for Sammamish, November 26th and 27th. It seems we're the only luckee duckees, because it's not even being predicted for Issaquah.

  19. Cliff ~ Hope you had a great Thanksgiving and a well deserved weekend off!

    The NWS put a "note" in their longterm discussion and mentioned the following...

    "both the 06z and 12z GFS had a
    strong system possible around Tuesday December 7th for which it might be
    Worth keeping a weather eye."

    I know you've said before that when it is that far out to not get excited but I love wild weather!

    Can you give us more details on this possiblity on the 7th? Like strong as in winds? rain? snow? all of the above? The NWS didn't elaborate!

    Not to mention that maybe we might want to make sure we are prepared in advance if it's something that's going to cause wide spread power outages?



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