GeezerHiker

February 5, 2013

Winter Potpourri

Filed under: Hiking, North Cascades, Snowpack, Weather — Tags: , , , , — geezerwriter @ 1:02 pm

I’ve been kind of lazy about posting lately, so I have a backlog of weather-related things to spout about.

The Great Inversion of 2013

A couple of weeks ago western Washington experienced a protracted temperature inversion. Usually the temperature of the air decreases as you go to higher altitudes (during the daytime, at least) due to the fact that the sun’s energy heats the ground faster than it heats the air, whereupon the warmer ground proceeds to heat the air from below. This situation is a bit like a pot of water on the stove: the lower layers are warmer, but warm things (generally) are lighter, so we get an instability where the warm stuff rises and the cooler falls, and everything gets all stirred up and burbly.

At night the opposite situation often occurs, since the ground also cools off faster than the air, giving the common situation where there is a layer of cooler air near the ground, often causing fog and frost or both. Sometimes you’ll even see frost forming on the ground when a thermometer a few feet higher reads several degrees above freezing

But the thing that breaks that cold layer down and makes our daily atmospheric pot roil and boil was that business about the sun heating the ground – which doesn’t happen so much here in the winter. We sometimes forget what the sun looks like for extended periods of time. Anyways, now and then conditions converge that allow that frosty layer to persist for days and grow to hundreds of feet thick. And that layer is quite stable, with the heavier, colder air at the bottom and warmer at the top. Usually we think of stability as a good thing but in the atmosphere it has the downside that the air just sits there, allowing all the dust and nitrogen oxides and other crud that we are so good at spewing to build up and form a low-lying smoggy cloud that further inhibits the sun from warming the ground, and so on, and so on.

[You read further, and more authoritative words about this and other meteorological phenomena on Cliff Mass’ weather blog.]

Another side effect of the inversion was that it gave us an extended period without new precipitation, allowing the snowpack in the mountains to settle and consolidate and bringing the avalanche danger down into a comfortable range. Just a day before the inversion was broken by the arrival of a strong Pacific storm Amy and Jan joined me as we left the gloom of the lowland smog for a snowshoe outing near the Mount Baker Ski Area. We were only a few miles from town and a few hundred feet in elevation when we passed out of the inversion layer and the sun broke through.

Snow or Frost?

Snow or Frost?

As we continued up Mount Baker Highway along the North Fork of the Nooksack River just before the road turns and climbs steeply to the Ski Area, we were admiring the heavy layer of snow on the trees along the road when it occurred to me that there hadn’t been any noticeable precipitation for about ten days. Snow on the trees is a pretty common thing up in the mountains, but we were seeing something that you usually see the morning after a heavy snow – these evergreens are shaped to shed the snow pretty quickly. Furthermore, the trees on the surrounding hillsides, and even the tops of some of the taller trees, were completely bare, so the snow was not fresh – how had it hung around for so long?

I puzzled about this most of the day and it wasn’t until we were on our way back to town that it made some sense. Maybe that snow wasn’t snow at all but a heavy layer of hoarfrost that had built up for days. Or maybe a combination of both. There is a phenomenon in the mountains called “cold air drainage” which results in localized inversions – the cold night air drains down the river valleys and picks up fresh moisture from the unfrozen river. While we were above the level of the coastal inversion, the calm stable weather meant that there were no windstorms to knock the snow off the branches. The sun had melted the tops of the trees but the snow had persisted or even grown with hoarfrost in the shade along the river.

Southern Sky

Southern Sky

I wish now I had spent more time trying to get some better pictures since this was such a combination of things that I might just never see it again.

We had a beautiful day for snowshoeing although the weather system that would ultimately break the inversion down was heading in from the west, making for some interesting skies. On the picture on the right you can see in the clouds a dark V-shaped pattern pointing toward the sun – just one of a number of odd fantastical shapes that we saw.

I will tack a picture gallery at the end of the post.

A Return to Normalcy

The "View" Point

The “View” Point above Cedar Lake

Loons on Cedar Lake?

Loons on Cedar Lake?

That snowshoe outing was on Tuesday, January 22, and by Thursday the inversion was pretty much gone and we had a nice sunny hike to Alger Alp. [As always, you can read about that hike on Jan’s blog, D-Jan-ity.] But another week later we were back to full-blown normal, a bunch of crazy geezers hiking in the chilly rain to Pine and Cedar Lakes. After visiting the lakes we hiked on over to Raptor Ridge, not so much for the view but because of the overhanging rock ledges that form shallow caves and provide some shelter from the wind and rain.

The State of the Snow

This morning I dug out my spreadsheets from last year that I had used to compare the snowpacks for the last several years and updated them with this the current Year-to-Date data in an attempt to get an idea of what this year’s hiking season might be like. The last two years have seen abnormally high snowfalls in the mountains which have delayed and disrupted our high country hiking. Here is the new graph:

Snow Depth (Water Equivalent) at 4900' near the town of Glacier

Snow Depth (Water Equivalent) at 4900′ near the town of Glacier

The blue line is this year so far and the red is an average for the last ten years or so, with the most extreme years (2006 was very low and 2011 & 12 were very high) omitted. [That “moderation” of the average seemed reasonable last year when I started doing this, but maybe there is a new “normal” developing?]

This year’s line is a little above “normal” but not enough to make a prediction – it seems to be the late season snows that have the most effect on the hiking season. Notice that in 2011, the year they couldn’t open the road to Artist Point, the snow depth was pretty average until well into March but then it snowed like crazy through most of May and it didn’t clear until mid August. Last year was a bit on the high side at this point before the ceiling fell in and it snowed through April.

Snowshoe Gallery

Swift Creek Valley from Artist Point area

Swift Creek Valley from Artist Point area

And one in the bush

And one in the bush

A bird in the hand

A bird in the hand

taking flight

Trudging uphill

Trudging uphill

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1 Comment »

  1. Ah, the post I’ve been waiting for! Looking at last Thursday’s hike, I can see I didn’t miss anything much. I was swimming and walking in the sunshine, but I did miss all of you. Thanks for putting this up, Al, I will be back home in three days and will probably take a few days to have an official reentry. 🙂

    Comment by DJan — February 5, 2013 @ 1:53 pm


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