An early, heavy snowstorm blanked parts of the Chilkat Valley late last week. Local forecasters and weather experts said while it was an unusual event, historic data shows that it’s not entirely unheard of in the region.
Even though the National Weather Service was not predicting a big storm at the time, Eric Stevens was fairly certain Haines was going to get walloped by Monday. The avalanche forecaster, who watches weather models every day, said he’s gotten used to seeing how certain signals in the models play out on the ground.
In this case, the weather models were showing a strong push of cold air coming out of the Yukon, a push of warm air coming up from the south and a low spinning up from the Gulf of Alaska.
“So when I see that signal, because it’s rare enough that it doesn’t really happen that often – maybe once a year if we’re lucky, we get to see that kind of thing happen – every time I’ve seen that signal we’ve gotten a huge snowstorm. It’s usually our biggest storm of the year,” he said.
When he saw that signal on Monday, he said it perked his ears up.
“I continued to track it Monday, Tuesday, Wednesday – my confidence really grew that this was going to be a pretty good snowstorm,” he said.
Still, he didn’t trumpet his suspicions around town. But, it turns out he didn’t need to.
“I mentioned it to my sister first because she is putting a roof on the new house that she is building,” he said. “She needed to clean up the tools and I was like ‘hey, get this done before Thursday because Thursday night we’re going to get a foot of snow.’ Apparently, she went around and told a bunch of people for me.”
As he predicted, it started snowing heavily and didn’t let up. The remote automated station at Ripinsky Ridge showed 24 inches of snow.
Stevens said he knows a lot of people are talking about the unusual weather event, and some have attributed it to global warming or climate change.
“I can understand the inclination to feel that way. But, just looking at how the weather models evolved on this, I don’t think it was a particularly extreme storm. It wasn’t stronger, or wetter, or colder than we usually see this year. It just happened to line up in exactly the right way,” he said.
Haines weather observer Jim Green said the Haines townsite was the bulls-eye for the snow event. Green, who runs the town climate station known as Haines #2, laid it all out in a blog post and interview after the storm.
Skyline drive saw 20.5 inches, a weather spotter in the northwest part of town reported 22.5 inches, and Green measured 19.3 inches Thursday morning through Friday evening.
Green said the data shows rain will switch over to snow close to Halloween – and historical data bears that out. The first measurable snow almost always occurs between Oct. 15 and Nov. 15 in Haines, according to his calculations.
So this year was early, but still common. And, this storm was one of the biggest of the October snows on record, according to Green. He said it just barely edged out a 99-year-old record.
“Technically, we set a record for the greatest 2-day snow in October,” he wrote in his williwaw.com blog post.
But, that assertion comes with a few important caveats.
The first is that measurable snow means 1/10th of an inch or more. But looking at the historical records – Green said a suspect number of them end in 0.
“[It] makes me think the observer was measuring to the nearest inch and not to the nearest 1/10th,” he said.
Additionally, there are 16 years of data missing between 1956-1972, meaning there were no official observations taken during those years in the Haines townsight.”
And, much of it is available was gathered by trained weather observers.
“The observers, like me, are volunteers and they have lives and there’s no guarantees that they’re going to be able to be out there and measure it whenever it stops snowing versus the next morning,” he said. “I think the data from these human observers is basically accurate, but it’s not as precise as it might be.”
Green said the historical record Haines broke was set on Oct. 14-15 of 1926 when the 2-day total snow was 19 inches. But due to the rounding issue and the different measuring locations, it’s not a straight comparison between the two measurements.
“So, who can say we really beat it?” he wrote.
What caused all of the snow? Green said the most common cause of snow in this part of Alaska is due to a phenomenon known as “overrunning.”
Essentially warm air is forced upward when it collides with cold air which is heavier.
And because large mountain barriers tend to affect air masses – the battle tends to happen close to the mountainous coast in Southeast Alaska. Green plotted out the maximum 2-day total snowfall in Alaska and at the top of the list are communities in northern southeast Alaska and west up through the Prince William Sound.
The clash between two fronts and the cold temperatures meant that Haines got almost two feet of snow before everything drifted south and dissipated near Juneau.