Ask a climatologist: Alaska’s spring weather whipsaw

The Chilkat Range visible on a clear, hot day at Eagle Beach on April 16 in Juneau. (Rashah McChesney/KTOO)

Alaskans have seen flip-flop weather develop in just a few days this April. That’s not necessarily because of footwear choices, although some folks probably are busting out their sandals.

No, we say flip-flop because there were record lows around the state from April 7 to 11, and more recently some places are already setting record daily high temperatures.

National Weather Service climate researcher Brian Brettschneider, back for our Ask a Climatologist segment, says it’s a remarkably quick switch.

Brettschneider says just a little over a week ago, places like Bettles and Atigun Pass were recording their lowest-ever April temperatures, while Anchorage and Fairbanks — the latter dipping to minus 29 — hit record daily lows.

Read a full transcript of the conversation, with minor edits for clarity.

Brian Brettschneider: If you look at the recent statewide temperature lows, it had an ‘unusualness measure,” if you will, of about once every 15 to 20 years. So about every 15 or 20 years, you would expect a day to be that much below normal temperatures.

And then by the time we get to this weekend on Saturday, many areas were 10-15 even 20 degrees above normal. Klawock hit 75 degrees, which is the earliest 75 degree reading for any station in Alaska in any year and it broke that record by three full days.

Juneau had their first 70-degree day of the year, and it was their earliest on record by a week and a month sooner than normal. Record warm today in Anchorage, (editors note: the day this interview was recorded, Anchorage hit a daily record 61 degrees) and just lots of sunny conditions, high pressure and snow melting really rapidly.

Casey Grove: That’s quite a flip. How common or uncommon is it to whipsaw like that?

BB: Well, everyone’s probably heard of the jet stream and when the jet stream dives really far south in one area, it has to compensate for that somewhere else. So in this case it has to kind of shoot way up to the north somewhere else.

So on any one given day you might have an area that’s way above normal and then an area a few 100 miles or 1000 miles away that’s way below normal. That’s not that uncommon.

What’s less common is for a single location and our latitude to kind of go from the deep freeze to the sauna in such a short period of time. Especially this time of the year where there’s still snow in the ground and the rivers are still frozen. It’s much more noticeable than if a big flip occurs, say in December or January.

CG: I wanted to ask you more about that. I mean are there concerns from that whipsaw effect that people might want to look out for?

BB: From a weather and climate point of view, of course, the concern with melting snow would be overland flooding where streams and rivers are still full of ice and so the water has a hard time getting into the river channel or storm drains might be frozen in the cities and the water can’t drain.

Of course, there’s also the concern about large amounts of fresh water pushing against ice and causing what we call a dynamic breakup. There’s no indications of that yet but that’s something that historically has happened at times when we have early season warmth like this.

CG: We’re talking breakup, coming and in some places already happening. So, is this it? Can we winter is over and then we’re done with that?

BB: In the cities, we think of breakup as the snow melt. Off the road network, breakup is the rivers breaking up. In the cities we’re well on our way to melting out the snow. Of course, the ice hasn’t broken on any of the rivers yet, but as far as wintry conditions – snow and ice and freezing – you can pretty much stick a fork in winter. It’s done.

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