Cold Days Ahead

January 2, 2017

9:45pm Monday…

We could all feel it today…the cold and dry air has been pouring into the Pacific Northwest the past 24 hours.  The peak easterly wind gust at PDX has been 36 mph this evening and temperatures are below freezing.  As a result you feel the windchill temp, which is now in the teens!  Dewpoints are dropping quickly too, that’s a measure of moisture in the air.  It’ll be very dry the next few days.  The air mass doesn’t cool much more in the next 24 hours, we’re just about finished with the advection of cold air into the region.  Looking at the Troutdale profiler, you can see the increasing depth of easterly flow coming out of the Gorge and over the Cascades since last night at this time.  The most current sounding is on the LEFT side of the image.  Time goes from right to left.  I added the thick blue line.

capture

With the upper-level low just offshore (and moving very slowly farther offshore) snow showers were very persistent today.  Basically the forecast busted with clouds and snow showers instead of mostly sunny.  Salem ended up with off/on snow much of the day.

Outlying areas west of the Cascades that clear out AND go calm tonight (not many areas do that) will see temps down in the teens tonight.  Most of the metro area stays in the 20s due to the wind.

Speaking of wind, it peaks tomorrow night and Wednesday morning with gusts in the 40-50 mph range in the east metro.  This will be enough for some power outages and trees down.  Not a massive east wind storm, but enough to cause some trouble.  The wind backs off dramatically Thursday and Friday.

Models have come into very good agreement on the Wednesday system crossing southern Oregon; the ECMWF was right, it’ll stay dry over the north/central Willamette Valley or we just get a few flurries.  All the main snow action will stay to our south and east.  But what a storm it’s going to be down there!  Check out the WRF-GFS snow forecast…

or_pcp24-48-0000

big snow across much of “Oregon’s Outback”.  Not a good day to drive in the triangle from Bend to Burns to Lakeview & Klamath Falls!

High pressure weakens a bit Thursday and Friday, thus the lighter east wind.  So I lowered PDX low temperatures.  With clear skies, dry air, and a cold air mass we may actually get down into the teens even in the city.  For sure in outlying areas.

Models have come into much better agreement on our “transitional event” Saturday & Sunday.  It’s a classic setup for brief snow and then freezing rain across much of at least the northern Willamette Valley and into the Gorge.  It may only last Saturday and then we warmup Sunday, or it may take until Sunday night or early Monday to get rid of the cold air.  A couple of brief thoughts on it now:

  1. I’m leaning toward freezing rain more than snow due to system coming in from the southwest with relatively warm temperatures above coming in quickly.   Snow levels jump to around 4-5,000′ with this system and the deep cold air over us is gone by that time.
  2. Pretty good agreement that Saturday is the day
  3. The low-level atmosphere over us Friday doesn’t go anywhere until at least sometime Sunday.  Easterly flow out of the Gorge continues through that time and there is no sign of warming southerly surface wind until Sunday at the earliest.

Chief Meteorologist Mark Nelsen