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February could start colder and more active thanks to the ‘PNA’ weather pattern

Published: Jan. 25, 2022 at 7:10 PM CST
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BISMARCK, N.D. (KFYR) - We’ve seen some big temperature swings this month with Arctic and Pacific air close by, but looking ahead to the start of February, there could be a change that leads to more active weather.

For longer-term weather trends, meteorologists often look at patterns all around the globe for clues as to what could happen locally in the coming weeks and months. These patterns are referred to as teleconnections and one of them, in the Eastern Pacific and the Western U.S., is called the Pacific North American pattern, or PNA for short. It has two phases, or states, positive and negative.

The positive phase, which is what we are in right now, usually favors above normal temperatures in the Western U.S. and below normal temperatures in the east, with storm systems riding along the jet stream in a way that favors Alberta clippers to form and track through our area, which we’ve seen recently. This pattern also allows for snow to reach the southeastern U.S. and bigger storms to ride up the east coast, which is predicted to happen this weekend.

Positive PNA phase: typical orientation of the jet stream and where colder/warmer air usually are
Positive PNA phase: typical orientation of the jet stream and where colder/warmer air usually are(KFYR)

When the phase of the PNA switches to negative, the pattern is flipped with below normal temperatures favored in the Western U.S. and warmer conditions in the east. This also allows for storm systems to dive south in the west and through the Rockies, before sometimes developing into larger storms, such as Colorado Lows, in the central part of the country.

Negative PNA phase: typical orientation of the jet stream and where colder/warmer air usually are
Negative PNA phase: typical orientation of the jet stream and where colder/warmer air usually are(KFYR)

Looking back at how the PNA has evolved this winter, it was negative for December and the start of January when we had above normal snowfall and long-lasting shots of Arctic air. Then the phase switched to positive over the past couple of weeks where temperatures have been milder for the most part and less snow has fallen.

PNA pattern since the start of winter and what it means for North Dakota's weather
PNA pattern since the start of winter and what it means for North Dakota's weather(KFYR)

This positive phase is expected to continue through the end of January with milder temperatures and not much snow, before flipping to negative around February 1st leading to more Arctic air and possibly more snow.

PNA pattern favored for the next couple of weeks and what it means for North Dakota's weather
PNA pattern favored for the next couple of weeks and what it means for North Dakota's weather(KFYR)

One forecast for February 2nd through February 5th shows high confidence in below normal temperatures for the Northern Plains and Western U.S. during this period.

Forecast for February 2nd through February 6th with colder temperatures (blue shading) favored...
Forecast for February 2nd through February 6th with colder temperatures (blue shading) favored over the central and eastern U.S. and warmer temperatures favored over the eastern U.S.(KFYR)

And the outlook from the Climate Prediction Center for the start of February shows this trend as well with colder air favored across the west and in the Northern Plains, along with above normal precipitation chances favored in our area, possibly leading to a more active pattern.

Precipitation trend for January 31 through February 4
Precipitation trend for January 31 through February 4(KFYR)

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