50 below zero in Oregon? It happened once. Plus weekend cold weather update

Have you ever wondered how cold it can get in our region? A winter low temperature of 20 degrees is somewhat normal west of the Cascades, 10 only happens every decade or so, but down to zero? Or below? It HAS happened, but it’s rare.

I’ve collected the “all-time” record lows from across Oregon in these graphics. Of course all-time means in the historical record of the station. Some records only go back to 1950, some well back into the 1800s. I don’t think any of the stations below go back before 1870. First the coastline

Then the western valleys and Mt. Hood

You’ll notice lots of those record lows are from the December 1972 cold spell. Here in Portland there is still a 10 day stretch in early December in which every daily record cold high temperature is from 1972.

East of the Cascades, those record lows are MUCH colder. That’s to be expected since in general it’s colder all winter east of the mountains.

The state record of -54 degrees was set at both Ukiah and Seneca during the same cold spell in February 1933. By the way, Washington’s all-time record low is -48 degrees.

WHAT’S THE PLAN FOR THIS WEEKEND?

Not much has changed the past 24 hours except for two items

1) Models have backed off a bit on intensity of the cold airmass moving in Saturday night and Sunday

2) It’s very clear now that showers end Saturday evening before temperatures get down close to freezing = no sticking snow

This graphic summarizes your snow chances well. No sticking snow west of the Cascades at the lowest elevations. It’s possible that only a dusting/trace falls even up at 1,500′. I think there’s a chance of 1″ or so in the central/eastern Gorge, but even that could be a stretch. The issue is that the system is moving very quickly = not much moisture to work with.

Our GRAF model shows the timing well. Around sunset Saturday temperatures will be around 40 degrees with very light/spotty showers. Modified arctic air (cold and dry) is pushing south into northcentral and northeast Oregon. But notice the air isn’t as cold as what we saw in December. I’d estimate about 10 degrees warmer

Then by 9pm, the “arctic front” has passed through the metro area. A gusty northeast wind has arrived, but since the arriving airmass isn’t that cold, temperatures are still well above freezing. Showers are finishing up; remember the upper-level system is moving quickly southward and heading to California.

By midnight, or soon after, the cold/dry air has taken over. Showers are gone and skies are mainly clear. But the gusty east wind is STILL keeping temperatures above freezing. That will allow any wet streets to dry before late night freezing; more good news for Sunday morning. No snow and no ice

A summary...

So instead of highs in the low-mid 20s (cold spell just before Christmas), we’ll see highs 10-15 degrees warmer PLUS sunshine all day Sunday. Sure, windchills will be in the 20s Sunday, but reasonable if you have a good winter jacket ready to go.

I do expect 8-15″ new snow in the Cascades the next two days. So very good ski conditions on the mountain with fresh snow Saturday and then a cold day Sunday. Luckily models have backed off the extreme cold in the Cascades. Temperatures will at least make it to 10 degrees up there; think Rockies or Utah ski conditions. Bluebird day Sunday!

The main message for the upcoming weekend is that we’ll see a dramatic change between Saturday and Sunday, and it’ll be quite chilly Sunday.

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