December 06, 2009

Snowy Sequim

A few cam shots around Sequim below (Sequim Lavender farm and Pt Townsend Airport) . Looks like they received around 1/2-1 inch of snow last night.

Temps are relatively warm today due to the clouds associated with the weather disturbance that moved through last night and this morning...but clearing will spread over the region today and the real cold is expected tomorrow morning. I spent some time yesterday preparing my home and plants...mulching them and moving some into the garage....they are ready!

Strong NE winds are coming out of the Fraser...some gusts to 30-40 mph in exposed locations last night (a few even higher). Look at the wind graphic below. On the figure there is both temp (upper left) and dewpoint (lower left). You will note the dewpoints are very, very low (single digits)--a sign of continental, arctic air. Look at the winds taken by the sensors on Washington State Ferries- strong NE winds...with 38 knots in one channel. Wa Ferries does a very important public service by having such observations....and there are available for you to view on the web site...Ferry Weather (
Finally, it will be very cold tonight and Tuesday morning...lots of places will see lower 20s and teens west of the be ready!

By the way, several of you have asked about a line of clouds stretching southwest of the Olympics (see figure). You know what this...the anti-Puget Sound convergence zone! The winds aloft are from the NW and the winds are passing around the Olympics and then converging in the lee of the mountains. Normally the winds are westerly when we get a convergence zone over Puget Sound, but now the winds are coming from the opposite the convergence switches side. Converging flow causes upward motion and clouds! You notice all the clouds offshore..that is cold air that has passed offshore and the atmosphere going unstable at low levels, as cold, dense moves over warmer water. Big change in temperature with height produces convection (cumulus to cumulonimbus).


  1. It seems that we in the San Juans can blame Canada for almost all our wind problems.

    In November, our damaging high winds were caused by a series of lows over Vancouver Island sucking air into Canada.

    Now in December they dump their Frazer Valley air on us with more high winds and cold.

    Perhaps we need to erect a tall weather fence at the border, to keep their weather in Canada and ours here in the US!

  2. Reporting 1/4" north of Clinton on Whidbey Island

  3. Here on the ridge 3 miles south of Chehalis, we have about 1/8th of an inch of show, maybe a little less. Low temp seems to have been 29F. RobLL

  4. Cliff,

    Cool events going on. Todays high of 27 at midnight. Currently 22. We also received a blanket of snow, but woke up to it being completely gone. Sublimation i believe. Gusty NE, making the sky hazelnut. Must be blowing dust again to the east.

  5. Winds in Lacey are G U S T Y.

    21 mph sustained, gusting to 32 mph right now.

    This turned into a mini-wind event.

    Power has even flickered once.

  6. 22mph gusting to 33mph in Lacey!

    This is becoming a longer wind event than I had interpreted from the forcasts.

  7. Hi Cliff -

    Can you provide us with some perspective on how quickly this Rex block (Omega block) can break down? Some of the models are breaking it down by next weekend.

    When it breaks, is their a likelihood, based on history, for a significant push of moist air?

    Thanks, Brian

  8. Cliff,
    I notice on the visible sat, that there’s a plume of clouds near the Olympics that stretcher’s SW all the way over the Pacific… is this a CZ?

  9. 19mph gusting to 38mph in Lacey.

    Did a low travel closer to SW Washington or something?

  10. Mid 30s sustained wind all day in the Haro Strait (Kelp Reef buoy).

  11. "It's beginning to look a lot like split flow, everywhere you go...."
    El Nino really starting to set up now?

  12. Probcast is saying that we should expect lows of 11 degrees tonight and 7 degrees tomorrow night... Is there a problem with that system?

  13. Still pretty windy here in Bellingham, with wind chills close to single digits. Curse you, Fraser River Valley. As usual, I blame Canada for this.

  14. Places in California are seeing snow for the first time in over 50 years. Very low snow levels in the Sacramento Valley. Though it seems we are setting up a split flow (El Nino) this is not your typical El Nino event for California.

  15. Well, the wind caused a tree to fall down in Lacey, across the road...and it fell on main power lines.

    No, it wasn't one of the "giants"...but it was a larger old tree that decided it had enough of the East winds.

    Power was out for 7 hours or so.

    This wind seemed stronger than forcast...I wonder why?

  16. @Rod in Seattle: I asked Cliff that very question about Probcast a day or two ago, and he said that this kind of cold, clear, still weather is the system's Achilles Heel; I've noticed that temps when the weather is like this are typically wrong by 10-14 degrees (too low).

    For instance, for my ZIP, 98008, last night they were calling for 11. Our actual low recorded on a professional weather station 0.8 miles away was 23, and on a semi-pro setup here at our house, we had 18.9F.

    For a quick rule of thumb, when it's clear and cold out, take the Probcast temp and add 10 degrees to it.

    HTH... you should go back I think two entries and read Cliff's response to me, if you'd like.

    I love Probcast, but I wish there was an "About Cold Low Temps" link on the page that explained this information to everyone. I really hate to see such a great site lose credibility over a known issue that could be explained in a way that would educate folks and make them trust the site MORE.

  17. Oh, and that 18.9F is at 281 ft elevation about 1/2 mile west of Lake Sammamish in east Bellevue. That's not our low for the year but it's definitely the coldest since the spring!

  18. I'll repeat Rod's comment. Went to Probcast this morning and almost spit my coffe on the keyboard. I can take 20-ish, but 7. Ouch!

  19. Air Quality will become an issue as the week progresses. FYI use this link for forecasts and current conditions.

  20. All,
    There is something wrong with probcast. Some people here are checking on way it will be that cold...hopefully we can find out the problem quickly...cliff

  21. Might be due too the negative dewpoints today. Calm winds tonight and the temperature cooling within ten degrees of the dewpoint, it would yield a forecast of 7.

  22. Are the ferry wind numbers considered reliable? There have been times when I have been kayaking near a ferry route, and noticed only insignificant winds (meaning 10 knots or less) and checked the ferry data later and seen records around 20 knots for the same time frame. I've since been suspicious that the corrections for their vessel speed are not always successful.

  23. Cliff, Just read the forecast disscusion for next weekend. Are we looking at a repeat of last year I saw snow all day for saturday.

  24. Rob, what discussion are you talking about? I haven't read any snowy Saturday forecasts?


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