Snow arrives as expected today, but morning commute should be okay for most of us

It’s hard to believe, but Portland broke a snowfall record today with 0.1″ officially at the National Weather Service forecast office just east of the airport (122nd & Sandy area). Wait for it...the big total...

Yes, just 0.1″ officially fell and that is a record for the date. We’ve never had more than a trace on December 4th. That’s a testament to how little snow we get (most of the time) in our mild maritime climate. BTW, yesterday’s record is still just a Trace (in 1972), and tomorrow’s record is 1.5″ (also in 1972). That was at the beginning of a tremendous blast of arctic air that settled over the region for just under 2 weeks. I was only 3 and don’t remember, but I probably went sledding with older siblings on my parent’s orchard farm near Oak Grove in the Gorge. But I digress... Here’s a look at December snow the last few years, with some help from Santa

I think ALL of us from the metro area north and eastward at least OBSERVED snow in the air today, for quite a few hours. But temperatures were too warm for many of us OR the precipitation was too light for snow to really start sticking on the ground. We picked up less than .20″ worth of rain/snow today...very light stuff and models showing light precip were correct. Troutdale likely had far more than .02″, but wind-blown snow has trouble making it into the gauge.

A few more totals for you...lots of other 1/2″ totals didn’t make it into this graphic as well

In the end, I am pretty happy with the forecast; we expected a minor event, but some “sleddable” snow in spots and that happened. These marginal snow situations are such a pain to forecast. If it would have been 3-5 degrees colder, widespread snow would have stuck to roads throughout the metro area. Models sure nailed that quick evaporational cooling this morning. There were doubters as PDX sat at 40 degrees all night and was 41 at 8am. But as soon as precipitation fell into the very dry airmass, temperatures cooled quickly down close to freezing and have stayed there since. 41 at 8am down to 34 at 10am...impressive

Now the airmass is pretty much saturated, plus warmer air has moved in overhead so no more snow.

MONDAY MORNING COMMUTE

Temperatures are still hovering just a few degrees above freezing tonight, so the big question is “Will all these wet roads freeze?”

The short answer is NO, for most of us. There will be some spots of freezing, but my gut feeling is we won’t be seeing widespread icing of roadways for the Monday morning commute in the I-5 corridor from Longview to Albany (our viewing area). There is plenty of cloud cover overhead and models imply we won’t see much clearing. The low level airmass is saturated. You’ve got to have clearing to have temperatures cool and roads freeze up. Plus there’s no fresh supply of cold/dry air coming out of the Gorge; pressure gradient is down to just 3-4 millibars across the Cascades. Last night at this time it was approaching 10! A lot less wind even out there.

One place that does stay frozen is the Gorge. Temperatures there are still all below freezing east of about the Corbett exit at freeway level. There have been numerous crashes out there in the past few hours. There is no warming westerly wind coming into the Gorge tomorrow, so you’ll only just rise a few degrees above freezing.

That’s it for now. Weather will be quite benign with very little rain through Wednesday, then a series of wet system arrives beginning Thursday and heading into the weekend.