How Anchorage’s ‘flufftastic’ snowfall exceeded forecasters’ expectations

Snow piled high on top of a bird feeder after a storm in Anchorage dropped over a foot of snow in some areas on November 11, 2021. (Julia O’Malley/Alaska Public Media)

Anchorage residents went to bed Wednesday night expecting some snow in the morning. When they woke up, though, it was more than double what had been forecast.

National Weather Service climate researcher Brian Brettschneider — back for our Ask a Climatologist segment — says there are a couple reasons for that.

The snow was very fluffy, due to some very specific atmospheric conditions, Brettschneider says, so being less dense, it made a thicker carpeting on the ground, and everything else.

And, he says, forecasters suspected there’d be a narrow band of heavy snow, but predicting where it would end up is extra tricky.

The following transcript has been lightly edited for clarity.

Brian Brettschneider: So the heavy snow was always on the table, although I think the maximum amounts have surprised pretty much everyone. But the the potential for heavy snow had actually been there for a while, it was a low-probability event at any given location.

Casey Grove: We went to bed last night, where my house is it was pretty bare on the ground, and woke up with almost a foot of snow. What were the totals around town?

BB: Well, as we’re talking, most places in town east of, say Minnesota drive have had 10 or more inches, and almost every place east of Seward Highway has had over 12 inches. And a handful of places have had 16, 17 inches. So it’s really been a big snow bonanza. As of about 1 o’clock, the official measurement was 5.6 inches. So the spot that has the lowest of any place in town, is our official total. So that’s kind of unfortunate.

CG: Yeah, not a bonanza for them. So something my editor asked me as I was coming in here, she said, “I’m very interested in the fluffiness factor.” And I wondered if there was a way of getting at that. Is it champagne powder? I described it as flufftastic. But I don’t know if that’s a technical term.

BB: Well, we, in the science community, we absolutely use the term “fluffy.” We’ll talk about how fluffy the snow is. Now, there are ways to quantify that. And really, what we talk about is what’s called the “snow-to-liquid ratio.” And so if you take the snow, and you melt it, and you end up with liquid, if you divide the snow divided by the liquid, you get your snow-to-liquid ratio. So for example, if you have 12 inches of snow that falls, and you melt it, and you end up with 1 inch of water, you take 12 divided by one and you get 12. So 12-to-1 is your snow ratio. If you have 24 inches of snow, and you melt it, and you end up also with 1 inch of water, we would call that 24-to-1 ratio snow. And in this case, this is a very low density snow. I’m estimating, you know, probably in the 20-, 25-, even in some cases 30-to-1 ratio in general. Here in Anchorage, we average about 15-to-1. So we’re kind of close to doubling that. So this is kind of double the fluffiness.

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Casey Grove is the host of Alaska News Nightly and a general assignment reporter at Alaska Public Media with an emphasis on crime and courts. Reach him at cgrove@alaskapublic.org.

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