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At a Glance The central and eastern U.S. states are seeing milder temperatures after a bitterly cold start to 2018.

A pattern change will likely bring a return of Arctic air to parts of the Rockies, Plains and Midwest for the beginning of February.

February will begin with a weather pattern change that will bring a surge of Arctic air back over a large swath of the nation, erasing the mild interlude many are enjoying right now.

The recent warmer weather in the Midwest, South and East is the result of a reconfiguration of the jet stream into a broader west-to-east flow. Passing cold fronts do knock temperatures down, but not to the extreme levels we saw in late December and the first half of January.

In general, temperatures should remain near or above average for late January in most areas east of the Rockies into at least part of next week.

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During the final couple days of January and the start of February, forecast guidance depicts another large-scale weather pattern shift.

First, the jet stream will bulge northward over the eastern Pacific Ocean into Alaska. Downstream, the jet stream is forecast to buckle southward across Canada and into the United States.

This type of weather pattern is notorious for feeding a pipeline of Arctic air into the Lower 48 states.

Kicking off this potential return to shivering temperatures is a cold front that is projected to move across the Midwest next Wednesday into Thursday. Milder air will first engulf the eastern states ahead of the front.

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That cold front may just be the beginning of this potential weather pattern change since additional bouts of Arctic air could descend into the U.S. from the Rockies eastward, thanks to the aforementioned southward plunge of the jet stream, or trough, setting up.

This is the type of jet stream configuration that led to the prolonged cold snap we saw from late December into the first half of January.

<img class="styles__noscript__2rw2y" src="https://dsx.weather.com/util/image/w/0123-colder-feb.jpg?v=at&w=485&h=273&api=7db9fe61-7414-47b5-9871-e17d87b8b6a0" srcset="https://dsx.weather.com/util/image/w/0123-colder-feb.jpg?v=at&w=485&h=273&api=7db9fe61-7414-47b5-9871-e17d87b8b6a0 400w, https://dsx.weather.com/util/image/w/0123-colder-feb.jpg?v=ap&w=980&h=551&api=7db9fe61-7414-47b5-9871-e17d87b8b6a0 800w" > The potential large-scale weather pattern in play to start February.

"The large-scale upper-level pattern should become more amplified and the downstream trough will become better established. This will open the door for additional Arctic cold front(s) and clipper-like systems that can drive reinforcing shots of modified Arctic air into the eastern two-thirds of the U.S.," said long-range forecasters at The Weather Company, an IBM Business.

As with any extended weather outlook, there are uncertainties with the details this far out in time. Key questions include:

How cold will the air be relative to the average for early February? The colder weather pattern will likely affect the Rockies, Plains and Midwest, but how long will it remain locked there? If the cold air spreads into the eastern states, how quickly will it do so and how long will it last there? How far south will this cold air penetrate and how long will it last there? Will any major winter storms accompany this weather pattern?

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All of those finer details will be ironed out to some degree over the next week or so.

For now, enjoy the mild reprieve because you may have to bundle up again soon. After all, it's still the heart of winter.