Unfortunately for those who enjoy sun and warmth, the Willamette Valley is prone to inversions. This means that on the ~30% of winter days that it isn’t actually cloudy or raining, the valley is often trapped in cold, clouds, and fog while the mountains bask in springlike weather. About once a year or so, this process gets really carried away.
The last time this happened was on December 17, 2011, when at 2:15 pm Corvallis had 39 degrees while the top of Marys Peak had, briefly, 75.6 degrees. I don’t entirely trust that number, as there was no wind at the time and it’s possible the sun was adding a few extra degrees. If we accept the numbers, that was a 37-degree inversion.
This week has been setting up as a similar pattern. Subsidence (sinking air) high in the atmosphere warms as it descends and compresses, creating an odd warming-in-place with no big south winds required. The sun is the ultimate source of the energy, but in this case sun-warmed air rose and cooled far away, drifted over our region, then settled under high pressure and warmed again. At the surface, especially in mountain-bounded valleys, cold air is trapped beneath the warm air aloft, condensing into fog and clouds and preventing any sun-driven warming. Without significant wind to mix the air layers, this pattern can persist for many days, with endless gray and 30-34 degrees in Corvallis.
Looking at the weather models, today looked to be a pretty good repeat of that day exactly 13 months ago, so I determined to leave work early and pursue the Marys Peak summit. As it happened, at 2:30 pm the temperature on the mountain reached 73.0 degrees, while my weather station recorded 33. That’s a 40-degree inversion, a record in my time here and like nothing I have seen weather-wise back in Minnesota.
Getting up the mountain proved a bit of a challenge, as my plan was to drive as far as possible, then ski. There were two miles of road around 3000 feet that were good for neither driving nor skiing – bare pavement interspersed with deep snow. I managed to make it to 3300 feet in the Subaru making full use of four-wheel drive in slushy ruts, though I did get stuck twice trying to turn around at the top. I brought a shovel with that in mind, and with the snow not quite deep enough to get high-centered I got out fairly easily.
Spinning up the ruts on the last two miles.
I'm actually parked on a paved road here.
I stepped out of the car into summer – around 60 degrees and warm enough that I could comfortably ski in just a shirt and pants. The first section was sticky with fallen fir needles and cones, but skiing conditions were pretty good closer to the summit with a thin layer of soft melting snow over a firm base.
Road peering through between drifts. I wish the Forest Service would close the upper gate to keep out the big rigs and preserve the road for skiers.
Unmarked snow near the base of the summit meadow.
Skiing the wide-open meadow is a joy. It was soft on ascent but crusted over when I came down after sunset.
4:00 pm. 66 degrees at the summit (though it felt a bit more like 56 down on the snow). Looking over the sea of clouds that is the Willamette Valley, to Mt. Hood (left, 109 miles), Mt. Jefferson (center, 87 miles), and the Three Sisters (right, 91 miles).
The air was about as clear as I have seen it - I could just make out Mt. Rainier, 184 miles distant. I'm not sure if it's ever possible to see Mt. Shasta (224 miles) or if the Earth's curvature prevents it.
A self-portrait attempt at Kelly's "uncle Dave pose."
West toward Table Mountain (top level with the ocean) and the Pacific Ocean horizon.
Sunset with atmospheric lensing (light reflecting off of the inversion boundary) flattening the sun.
The atmospheric lens effect kept the sun appearing on the horizon long after it had actually set. Here the last rays are about to disappear, a full 10 minutes after the last photo.
The ruts were deeper going down as both I and a big jeep had dug into the soft snow going up. I'm not sure I could make it back up in this state. Might have to hike next time, or wait for new snow to ski this stretch.
Drove back down into cold cloudy winter, where Ebba and John had delicious homemade pizza waiting. As I write this (11 pm) it is still 54 degrees on the summit, 31.7 down here.
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