No Snow in Lowlands & Pineapple Express Next Week

November 17, 2011

I still don’t expect snow in the lowest elevations during the next 36 hours here in Western Oregon. 

For those just looking for the basics:

  • Sticking snow is still very unlikely between tonight and Saturday morning below 1,000.  In fact most sticking snow will be up around 1,500′ and higher in the metro area.
  • Beyond that, there is no threat for low elevation snow or ice in the next week or so; your Thanksgiving Week travel should be fine if you stay out of the passes.  Even those passes look mainly clear Monday-Wednesday as well with warmer weather.
  • No freezing this weekend, other than the usual light frosts we’ve already seen so far this Fall.

After perusing the 00z models, a few interesting tidbits stick out.  First, the surface low moving down the coastline should end up over SW Washington about this time tomorrow evening.  Look at the resulting pressure gradient.  WRF-GFS says 10 millibars southerly gradient from Eugene to Longview.  That’ll keep the air well stirred up and plenty of mild air moving in off the ocean.  One significant strike against seeing snow in the lowlands tomorrow evening.  Our RPM model is not as strong with the surface low, but it’s still to our north.

Soundings and cross-sections show the atmosphere cooling only a few more degrees in the next 24 hours.  The trend of very slow warming has continued for the past 48 hours.  Remember just two nights ago when we were seeing forecasts of -7 to -8 degree 850mb temps?  The 00z GFS very briefly touches -6, otherwise it’s only -4 to -5 tomorrow and tomorrow night.  I’m going to raise the forecast snow level up to 1,500′ based on this and meteograms/cross sections showing the freezing level not dipping below 2,000′ through Saturday morning.

Southerly flow, clouds, and rain returns Sunday night.  Then models ALL show a pineapple express setup just to our northwest Monday through Wednesday.  Flooding is possible in the far north Coast Range and all across Western Washington north of our viewing area with this pattern.  As of now, it appears we will be just south of the main rain band most of the time.  A very mild/warm spot to be.

It’s WAY out there at Day 8, but the 00z GFS has a deep low pressure system spin up just west of where we’d like it to be for a good windstorm.

Chief Meteorologist Mark Nelsen


Updated Pass Cams & Colder Weather Update

November 17, 2011

I just cleaned up the PASS CAM page (tab on the top of this page) to include all the new Hwy. 26 cameras and Coast Range cameras.  Enjoy.

After a brief look at morning models, not really any change in my thinking; snow still looks unlikely in the lowest elevations either tomorrow morning or Friday night/Saturday morning.  The mesoscale models have warmed a bit further, with neither the UW WRF-GFS or our RPM indicating temps/atmosphere cold enough for sticking snow below 1,500′ or slightly under.  On the WRF-GFS it’s real obvious why; the surface low tomorrow and early Saturday morning moves right over us and then off into SE Washington.  That’s farther north than previous runs.  Our RPM shows a similar setup; note the continuing southwest wind tomorrow night and Saturday morning keeping the temps up on the extracted text data:

Interesting to note the NAM continues to advertise a colder atmosphere than the meso-models do.  It would suggest at least down to a 1,000′ snow level both of the next two mornings.  I’m discounting it since the finer-resolution models are a little warmer.

As mentioned in the last post and reinforced by morning models; there isn’t going to be any cold shot of air now.  In fact I’m not going to worry about draining my drip irrigation and camping trailer water (did that sound a little “whiskey tango”?) until over the weekend.  We won’t get much clearing either Saturday or Sunday, and now it looks like a decent chance for showers or rain both days.

Chief Meteorologist Mark Nelsen