Back to Work: Wind & Snow

I still feel a bit under the weather today, but after looking at the weather maps I just couldn’t stay away!  Plus Andy is sick too so that leaves no one to cover me tonight.  What a team player eh?

First for tonight…nice pacific system moving onshore.  Looks like a good slug of heavy rain briefly overnight then back to shower tomorrow.  Deep low moving towards Queen Charlotte Islands.   A windy/rainy night but nothing too unusual for mid December.  By the way, don’t forget that today is the anniversary of the Dec. 12, 1995 windstorm.

Speaking of windstorms, all of our eyes are obviously scanning every single possible map/model for clues as to who is going to get hammered.  Of course as I write this there is no 00z model guidance available yet so I’ll post again later with my thoughts on 00z info.  It is pretty clear that a low is going to develop explosively and land probably on the NW Washington coast…they sure like to go up there don’t they?   You may recall that after November’s storms I decided the NAM-WRF is no longer my friend, so I’m leaning heavily on the GFS this time (that includes the UW-MM5 GFS).  As some of you have discussed at great length below…by the way, are you all employed?…there is a heck of a gradient to the south of the low as it moves onshore.  My 37 year old eyes could barely see the isobar packing between Portland & Eugene.  But I get 20-22 millibars from EUG-OLM!  The old rule of 3.15 x EUG/OLM gradient = 60-70 mph gusts in the metro area.  If so it’ll be a big windstorm from Eugene to Kelso.  But of course only a slight deviation in track to the north or a weaker cyclone could just give us the usual 45-50 mph.  Timing isn’t much of a debate…looks to be between 7pm-midnight Thursday evening.  I am impressived by the insistence through several runs of the GFS that there will be an "elongated" low with the big isobar packing over us.  It’ll be real interesting to see if it really sets up that way.

Now behind that storm a much colder airmass comes in.  Looks like a 1,500′ snow level at the lowest during the daytime Friday since it’s such strong onshore flow.  Remember that this is immediately following the gusty southwest wind and it’ll still be windy/breezy the rest of the day Friday.  I doubt we can get snow down to or below 1000′ in that pattern.  Then a quick shutoff of showers overnight Friday night and into Saturday morning when it’s finally cold enough for everyone to see snow.  With weak ridging then until sometime early Monday (via the ECMWF & 18z GFS), I just see a partly cloudy and chilly weekend.  Next system arrives from the northwest on Monday and pulls up southerly breezes again.  I see that as very similar to the late November one where the cold air was gone in a snap since the low is going by to the north.  For these reasons I’m downplaying the snow threat quite a bit.  Too warm Friday, too dry Saturday/Sunday, too warm Monday w/ precip…I’ll update later when 00z models arrive…Mark

11PM UPDATE: 00z models not too much different, landfall near the NW tip of Washington Thursday evening.  Notable again is the tight packing of isobars between 7-midnight over our region.  Hmm, could be a GREAT windstorm, but we’ll see.  It’ll be fast, over by early morning.

427 Responses to Back to Work: Wind & Snow

  1. Mback says:

    Correct loop just need to take the major storm graphics off eh. Nice of them to get my hopes up. LOL.

  2. Steve Pierce says:

    New comments coming in now from Mark. See other blog.

  3. Justin says:

    LOL, I do realize that, I’m speaking since January 1, 2000 only, which is still now about 7 years.
    BTW Phil, worst case scenario? I’d say Jacob’s forecast, which is certainly possible, but I do see that being the worst case scenario. Assuming the low really bombs, then 960ish could be possible, even the MM5 has had a difficult time at times this year estimating lowest central pressure, so take off 5-10mb from 971 and you could get the lowest central pressure. In which case the gradient would be mesmerizingly insane, 11-13mb for EUG-PDX and 15-17 for PDX-SEA. Lets just say that would cause a ton of wind, and widespread hurricane forced winds with a lot of damage unfortunately. Not to mention the Coast would just get pounded, I’d honestly not want to be on the Coast for this, it’ll be downright dangerous (possible MAJOR hurricane forced gusts, Cat 2 sustained winds)

  4. Rob -Southeast Portland- says:

    This model shows the system offshore developing.

    It’s probably a few hours old as this plots the low at 150W/40N, and on WV Loop it’s clear the low is now located at 147W/41N.
    The blue #’s you see I believe are the pressure rises/falls.
    The -negative obviously is falling pressure, and +duh Lol.
    I am not sure if the numbers reflect hourly changes in pressure, but I see some very impressive -0.50, -0.52, and a -0.60 pressure falls out ahead of the developing low.
    I also see a +0.30 behind the front.
    Any thoughts?

  5. Sandi (Wilsonville) says:

    Excuse my ignorance here, but when the wind “flags” are pointing more from the SW than the S, will that mean less wind, or does it even matter and we just look at the gradients?

  6. Boring Larry says:

    I’d like to point out that the century is only a few years into it…

  7. salemphil says:

    Ok, so what would be the very worst case scenario?

  8. Jared ---ASTORIA OR says:

    guys please enough about the windstorm can we just focus on the snow? haha just kidding this windstorm is going to be insane if it keeps on track like its showing, only anohter hour and the new models will be out

  9. Justin says:

    Michael, that PDX-SEA gradient would be a new record if the MM5 is correct. The old record is 15.4mb from January 20, 1993, I think we have a chance of topping that.

  10. Rob -Southeast Portland- says:

    Yeah and that only has the low at 971mb. I’m quite certain it’s going to be below that AND if it bombed as low as Jacob’s Mets at BPA said (955-964mb) then you can add more isobars to that. Sooo this could be “The BIG ONE” yeah?
    Any thoughts?

  11. Justin says:

    Holy crap on that MM5 run, that would be an amazing storm. Tons of rain and wind, perhaps it could beat out January 6-8, 2004 as the storm of the century for Portland? That still supports at least a +10mb EUG-PDX gradient, interesting fact is we’ve NEVER had a gradient that strong that has failed to produce at least 56mph at PDX, and if MM5 is correct then this storm will be very, very deep (960ish) (looking at current infrared, I can believe it). Historic windstorm on the way? I’m sure Mark will cover this tonight, assuming he’s feeling better.

  12. Michael Goss says:

    So.. the 12z MM5-GFS had a gradient of about 10mb from Portland to Seattle, and about 13mb from Eugene to Portland… a total of about 23mb from Eugene to Seattle.
    The 00z MM5-GFS has a gradient of about 16mb from Portland to Seattle, and a gradient of about 9mb from Eugene to Portland… a total of about 25mb from Eugene to Seattle.
    Just insane.

  13. Michael Goss says:

    According to the 00z MM5, Portland is about to get slammed. This is stronger than the 12z MM5 by 3 mb, and the center is further south.

    My GOD, look at those isobars!

  14. Jared ---ASTORIA OR says:

    has the weather channel said anything about snow or is it all focused on the wind.

  15. Andrew---Ellensburg, Wa and Portrland, Or says:

    Watching the weather channel really makes it feel like we have a monster heading towards us. A lot of their coverage today has been devoted to the incoming storm and now they have a weather advisory running across the bottom of the screen.

  16. Michael Goss says:

    Overall, the 00z GFS It decreases the moisture compared to the 18z… but it’s a really odd solution because there’s a low right on the Washington coast, and another one off the northern California coast… and yet the GFS refuses to throw moisture up at us.
    It DOES eventually give us a LITTLE snow out of it…

  17. Rob -Southeast Portland- says:

    Station 46532 – Drifting Buoy 141W/41N
    29.61in -0.13 (Falling Rapidly)

  18. Justin says:

    00z GFS looks nice and consistent for tomorrow night, shows 976mb at around Tatoosh Island, which I’d translate more to 966mb and within 50 miles of there. So definitely still on track for solid storm tomorrow night.
    As for snow, still really doesn’t look likely. New run shows no moisture over us Saturday, and just a tiny bit Sat. night. Surprise surprise!
    But still develops two tiny lows as Michael said, but keeps them weak and offshore. I’d say weak shower activity is about as much as we could expect from that. Even if we are cold enough, I see no solid storm whatsiever. Perhaps we’ll get a dusting Saturday, hopefully we are cold enough with some showers Friday night and get some light amounts then too, but it still doesn’t look likely and whatever we get will be badly overshadowed by the wind IMO.

  19. Michael Goss says:

    And ironically, while we’ve been talking about the 00z GFS, the MM5-NAM has been coming out. It shows a weak surface low forming off the southwest Oregon coast as well.
    The strength and placement of that low are uncertain, but it seems very likely that there WILL be at least some form of low off the coast this weekend. However, the strength and placement will be critical to determining how much snow, if any, falls.
    As for the windstorm, it is still looking brutal according to the 00z GFS.

  20. -100F says:

    This is what the 00z GFS did last night , it showed the low of the coast with no moisture making it in. Than 06z 12z and 18z all showed increasing moisture, all of a sudden the GFS removed most of it…

  21. Michael Goss says:

    The 00z GFS looks to make the 2 lows just sit off the coast.
    That would keep Portland under an offshore gradient, keeping it cold enough for snow.
    Now the moisture….
    The lows are relatively weak, and the GFS shows almost NO moisture inland at all. Still, with lows sitting right on the coast like that, I find it hard to believe that no moisture would be thrown up towards us.

  22. Michael Goss says:

    The 00z actually makes a double-low out of the trough… one in southwest Oregon, and one off the Washington coast. I’m not sure what that means. I’ve never seen a situation like that before.

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