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February Temperature Outlook: Mild in Central, Eastern U.S.; Colder in Northwest

Published in 21 January, 2021

At a Glance

  • There are several weather patterns that have grabbed our attention in recent days.

  • One of these is a weaker polar vortex, which could have an impact on the winter pattern.

  • These factors could lead to a colder, snowier central and eastern U.S. into February.

February 2021 may be warmer than average across much of the United States from the South to the Northeast, according to the latest outlook from The Weather Company, an IBM Business.

February’s forecast shows far-above-average temperatures are possible across most of the Northeast, as well as the Southern Plains. Above-average temperatures are also expected in parts of the Midwest, Southeast and Southwest.

Colder-than-average temperatures are possible in the Northwest and northern Rockies, particularly from Montana to Washington state.

Most other areas of the U.S. should see temperatures that are close to average.

Winter, so far, has been a relative non-event in parts of the northern U.S.

A persistently strong Pacific jet stream has spread warmer-than-average air into much of Canada and the northern states from the Northwest to the Plains, Great Lakes and New England.

Some cities from Seattle to Caribou, Maine, have had a record-warm start to winter.

But there are signs the pattern will have changed heading into February.

One change is that a sharper southward jet stream plunge – known as a trough – will carve itself into the western U.S., forced by a bubble of higher pressure aloft in the North Pacific Ocean poking north toward Alaska’s Aleutian Islands.

This pattern will “favor Arctic air transport into western Canada for the first time this winter,” said Dr. Todd Crawford, chief meteorologist with The Weather Company.

The proximity of this colder air in Alaska and western Canada increases the chance of a colder February in the Northwest and northern Rockies.

This pattern change, by itself, resembles a typical La Niña winter. Namely, colder in the Northwest and northern Rockies, and generally warmer elsewhere in the U.S.

The jet-stream level features we expect to be in place in February 2021.

But there’s one stubborn feature that could throw a large monkey wrench into that general La Niña outlook.

That’s the Greenland block, another bubble of high pressure aloft near Greenland that intensified after Christmas. Meteorologists also refer to this as the negative phase of the North Atlantic Oscillation, a sloshing of pressure difference across the North Atlantic Ocean.

Crawford suggested this blocking pattern may stick around at least through February, if not later, based on an examination of previous winters similarly dominated by this pattern.

“The North Atlantic blocking may allow for occasional Arctic air intrusions into the eastern U.S.,” said Crawford.

In other words, it may temper to some extent what would otherwise be a warm late winter in parts of the South and East.

This Greenland block appears to have already had an effect along the Gulf Coast and Florida, one of the few areas with a cooler-than-average winter so far.

The Greenland blocking ridge may extend southward into parts of eastern Canada at times. Thus, parts of northern New England may have the best chance of a milder February, as shown in the outlook.

You may wonder if the polar vortex has anything to do with this outlook. The short answer: possibly.

A sudden stratospheric warming (SSW) is an event over the Arctic when the stratosphere warms sharply – 50 degrees or more in just a few days – miles above the Earth’s surface.

One such SSW happened a few weeks ago, which weakened, stretched and displaced the polar vortex off its usual position near the North Pole.

A significant SSW event can sometimes have an influence on weather patterns in the Northern Hemisphere, reinforcing the blocking patterns such as the Greenland block.

That means this Greenland block could linger in some form into March.

Early Spring Sneak Peek

A gradually weakening La Niña and the potential for leftover Greenland blocking are the key factors leading into early spring.

“Lingering La Niña conditions are typically associated with hotter spring and summer outcomes,” said Crawford. “We think that spring and early summer will be unusually warm and dry across the western and central U.S.”

In March, most of the nation’s midsection may see far-above-average temperatures.

Concerns about Greenland blocking lead to less confidence of warmth spreading to the East Coast and Southeast. The potentially stubborn West Coast jet-stream dip could also put a cap on temperatures in the Northwest.

April outlook temperatures look much the same, with perhaps a better chance of warmth farther east, including the Mississippi Valley and Southeast.
Dry ground from the ongoing extreme to exceptional drought across the Southwest, Rockies and High Plains may contribute to the spring warmth in those areas.

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