Last Week of November = Mild & Wet At Times

November 25, 2018

6:30pm Sunday…

The long Thanksgiving Weekend was relatively tranquil with some much needed rain in the valleys plus mountain snowfall.  I was not in the area and spent the holiday down in the Las Vegas area.  Even lots my driver’s license while taking a run.  Unfortunately that means I got the FULL pat-down experience at the airport on the way home.  Not a big deal, but weird.  Models did pretty well showing that 15-25″ snow for the Cascades.  I see depth has settled down to around 17-18″ at both Timberline and Mt. Hood Meadows.  Maybe 6″ or so still on the ground down at Government Camp.  This is at 5,000′ from our Skibowl camera:


We have a very warm system offshore right now; a typical “atmospheric river”.  It will send plumes of subtropical moisture into Washington and Vancouver Island the next 24 hours, leaving most of Oregon dry until around sunset Monday.  Enjoy your dry Monday!  For many of you it’ll be warmer (mountains, coast, valley), but in the Gorge and Portland metro area we won’t warm much due to a low-level easterly wind inversion.

That wet system moves onshore tomorrow night and Tuesday morning.  We should see about an inch of rain out of that system plus the post-frontal showers Tuesday.  The mountains see all rain through early Tuesday, then go back to a rain/snow mix depending on elevation. There are hints that Tuesday morning/midday could see very active convection with models showing below zero lifted index, plus abundant CAPE.  Similar setups in the past have produced funnel clouds and/or weak tornadoes.  Not a guarantee we’ll see either of these of course; the point is that the weather setup is similar to those past events.

Beyond Tuesday, the Pacific jet stream becomes a bit more “confused & splitty”.  By that I mean models are all over the place with locations of upper-level and low-level low pressure areas.  Generally systems are weak with lots of energy headed south into California instead of the Pacific Northwest.  The 12z ECMWF model run decided to produce a big windstorm for NW Oregon and SW Washington this coming Saturday.  See the 976mb low at Ocean Shores?

Of course I immediately checked the ensemble members.  As I expected; only 9 of 51 members imply any sort of strong wind Saturday at Astoria.  Any of the yellow/red blocks are wind gusts 50 mph or higher.

So we can dismiss that idea for now.  As meteorologists we should always be looking at (and forecasting from) those ensembles instead of just one operational run.

Other than some rain at times, and some additional mountain snow at the end of this week, things look pretty quiet.  November is going to go down as a dry one with temperatures near normal.  Quite an uneventful start to our stormy season don’t you think?

By the way, the warm blob in the eastern Pacific has expanded and strengthened in the past month.  This is sea surface temp anomaly from one month ago:

Now it has shifted a bit closer to us as well as warmed a bit (compared to average).  At this point all of the northeast Pacific from the West Coast to about 1,200 miles offshore, then north to Alaska, is running warmer than average.

What effect that has on our winter weather I don’t know, but it sure won’t help in marginal snow situations when cold air pours out of Alaska and heads toward us over the ocean.  We’ll see.

Chief Meteorologist Mark Nelsen