After a brief break from the sub-zero chill in Southcentral, colder air will make a triumphant return to round out the week. A descending polar vortex could bring some of the coldest temperatures parts of Alaska have seen in years.  

Temperatures climbed back into the double digits (above zero) Tuesday after a rather cold few days. A weak front associated with an upper-level low north of the Aleutian Islands brought clouds and warmth back to the region. The front itself isn't strong enough to bring a pattern change, but another wave of energy Wednesday should keep temperatures above zero through the day. Our big change happens late in the week. 

Most major weather events start in the upper levels of the atmosphere. This is no different. The jet stream dips down into Southcentral Alaska late Thursday and Friday. This will allow the mass of cold air that spins over the North Pole to dip into Alaska as well. As it slides south, temperatures will plummet across the 49th state. 

This cold air mass that spins over the North Pole goes by another name: The polar vortex. The vortex received tons of negative press a few years ago for dropping temperatures across the eastern U.S., but this week it will do the same for Alaska. 

By Friday morning temperatures will drop back below zero in Anchorage, then stay cold through Saturday. Across the Interior, temperatures will approach lows we haven't seen since the 2016-2017 winter.

During the 2017-2018 winter the coldest day was 2 degrees below zero. We've already experienced a colder morning than that. Right now, temperatures are forecast to drop below that, and potentially lower than the 7 degrees below we saw earlier this week. Back in January 2017 we hit 15 below zero three days in a row. Thankfully it doesn't look like we will get colder than that this week.

Another bit of good news is that a building trough should push the polar vortex back out by early next week. Temperatures will climb back near normal next week as the chance of snow returns to the forecast. 

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