Major Stratospheric Warming Event Expected in February Could Shake Up U.S. Winter Weather

We are closely monitoring an unusual atmospheric event developing high above the Arctic that could significantly influence weather across the United States in February and beyond. A sudden stratospheric warming (SSW) a rapid rise in temperature and pressure in the upper atmosphere is now forecast to take place in early to mid-February and trigger a […]

We are closely monitoring an unusual atmospheric event developing high above the Arctic that could significantly influence weather across the United States in February and beyond. A sudden stratospheric warming (SSW) a rapid rise in temperature and pressure in the upper atmosphere is now forecast to take place in early to mid-February and trigger a collapse of the polar vortex, a large circulation of cold air normally centered over the North Pole.

What is a Stratospheric Warming Event?

Sudden stratospheric warming occurs when atmospheric waves push energy from lower levels up into the stratosphere, abruptly raising temperatures tens of kilometers above the surface and distorting the polar vortex. Under normal winter conditions the vortex helps keep the cold Arctic air bottled up in the far north. But when it is disrupted, weakened, or splits into multiple pieces, it can no longer contain that cold air, allowing it to spill southward into lower latitudes. These events are relatively rare but known to have large impacts on seasonal weather patterns.

What the Forecast Shows

Latest model guidance indicates a prolonged weakening and eventual collapse of the stratospheric polar vortex in early February, driven by a strong warming signal at the 10 mb level of the stratosphere. This collapse could split the vortex into separate lobes and shift the circulation, creating a high-pressure ridge near Greenland and low pressure extending from the eastern United States into the Atlantic. Such a pattern encourages cold, northerly flow into the central and eastern U.S. in the weeks after the stratospheric event.

We emphasize that there is a delay between the peak of the stratospheric warming and the surface weather impacts, typically ranging from 10 to 30 days. But once that coupling occurs, the result often includes a pattern favorable for colder than normal temperatures across large portions of North America.

Potential Impacts for the United States

Colder and more volatile late-winter weather is a possible outcome of this event. If the vortex collapses and the circulation becomes displaced, Arctic air may intrude far southward, increasing the likelihood of cold snaps, deeper snowstorms, and more frequent high-impact winter events. A disrupted vortex also tends to produce “blocking” patterns in the atmosphere, which can allow cold air masses to remain over regions longer than usual.

In previous winters, similar sudden stratospheric warming events have been associated with episodes of severe cold and heavy snowfall across the United States when the displaced polar air interacts with moisture and storm systems at lower levels of the atmosphere. We caution that while not every SSW leads to extreme weather at the surface, the conditions forming this February are unusual for this time of season and deserve attention.

What Comes Next

We will continue to refine the expected timing and magnitude of this event as February approaches. Because the atmospheric coupling process is complex, surface weather impacts such as specific temperature anomalies and storm tracks remain uncertain at this range. However, the emerging pattern underscores the possibility of a colder and more active late winter period across much of the United States should the stratospheric warming and vortex collapse fully materialize.