A major change in the weather pattern over North America is ahead. While much of the eastern U.S. has been frozen by rounds of Arctic air and snow, the West has remained unseasonably warm, which has left many mountain ranges in a snow drought. That is expected to change by mid-month, as a shift in the jet stream will open the door for numerous storms to bring snow and rain to the West Coast and Rockies. Additionally, this shift in the jet stream will shield the East from the worst of the polar vortex, which will retreat farther north than earlier projections.
While much of the eastern U.S. has been frozen by rounds of Arctic air and snow, the West has experienced weeks of unseasonable warmth, which has left many mountain ranges in a snow drought. A major change in the weather pattern will flip the script by mid-month, as a shift in the jet stream will open the door for numerous storms to bring snow and rain to the West Coast and Rockies.
Additionally, this shift in the jet stream will shield the East from the worst of the polar vortex, which will retreat farther north than earlier projections.
WHAT IS THE POLAR VORTEX?
COLUMBIA, SOUTH CAROLINA – JANUARY 31: A student slips and falls on the historic Horseshoe as snow falls at the University of South Carolina on January 31, 2026 in Columbia, South Carolina.
((Photo by Sean Rayford/Getty Images))
A United Airlines plane as snow is removed from the tarmac at Ronald Reagan Washington National Airport (DCA) in Arlington, Virginia, US, on Monday, Jan. 26, 2026.
(Photographer: Valerie Plesch/Bloomberg via Getty Images)
People walk in the snow in Central Park in New York City on December 27, 2025. New York City receieved around 4 inches (10 centimeters) of snow overnight. Airlines canceled 1,500 US flights during the peak holiday travel period Friday, with severe winter storm warnings and heavy snow forecast across parts of the Midwest and northeast. (Photo by TIMOTHY A. CLARY / AFP via Getty Images)
(Photo by TIMOTHY A. CLARY / AFP via Getty Images)
05 December 2025, USA, Washington: Snow lies in front of the Lincoln Memorial (background) during the first snowfall of the winter season.
(Photo: Thomas Müller/dpa (Photo by Thomas Müller/picture alliance via Getty Images))
Scenic shot of heavy snowfall in Chicago.
(Robert Ray)
The core of the polar vortex contains some of the coldest air on the planet and typically sits over the North and South Poles.
HISTORIC WINTER STORM KILLS OVER 80, IMPACTS MILLIONS ACROSS MORE THAN 40 STATES
But by late December, the polar vortex was displaced, with a lobe of that cold air parked over Canada. This opened a freezer door over the eastern U.S. that allowed waves of Arctic air to spill south.
Simultaneously, the Pacific-North American jet stream — the steering mechanism for most of the storms over the country — dipped sharply over the East, allowing those storms to tap into the Arctic air. This has produced weeks of bone-chilling cold and snow, including January’s deadly and historic cross-country winter storm.
(FOX Weather)
Meanwhile, that same jet stream pattern has locked in a ridge of high pressure leading to weeks of dry and warm conditions over the Mountain West and West Coast.
High temperatures have been 15–20 degrees above average, with record highs expected later this week — San Francisco is expected to reach nearly 70 degrees Wednesday.
(FOX Weather)
But a needed shake-up is expected to begin in the coming days into mid-February.
WHAT IS THE JET STREAM?
The trough of the jet stream will park over the West, ushering in rain and snow, while the ridge will move over the East, protecting that part of the country as storms are forced to ride around that area of high pressure.
(FOX Weather)
This comes as new forecasts show that the main lobe of the polar vortex will move more towards northern Asia and the lobe over Canada will retreat farther north than projected earlier this year.
WHAT ARE THE ARCTIC OSCILLATION, NORTH AMERICAN OSCILLATION AND MADDEN-JULIAN OSCILLATION?
Additionally, the Arctic Oscillation — essentially a ring of wind circling the vortex that allows the coldest air to escape — will tighten, reducing the amount of freezing cold outbreaks for the East.
The upshot is a needed return to winter for the West and cold weather relief for the East.
(FOX Weather)
Although the West initially benefited from the warmth after atmospheric rivers brought catastrophic flooding to parts of Washington and California in December, many mountain ranges are facing major snow deficits.
PACIFIC, WASHINGTON – DECEMBER 16: In an aerial view, a neighborhood is engulfed in floodwater on December 16, 2025 in Pacific, Washington. Evacuations have been ordered in 3 suburbs south of Seattle after recent levee failure. Atmospheric rivers are expected to continue in the coming days as northern Washington continues reeling back from historic flooding late last week. Mass flooding along the Pacific Northwest caused historic flooding, tens of thousands of evacuations, and dozens of Coast Guard rescues.
((Photo by Brandon Bell/Getty Images) / Getty Images)
These mountain snowpacks play key roles in providing water for drinking and agriculture during the summer months for a lot of communities throughout the Rockies and West Coast.
SNOWFALL IS CRUCIAL FOR LONG-TERM DROUGHT MITIGATION
The Northern Rockies in particular, are running 50–90 percent below their seasonal snow average.
The snowpack in the Central Rockies, which feeds the Upper Colorado River Basin, is at a record low.
(FOX Weather)
The Wasatch Range in Utah is between 25-90 percent below its seasonal snowfall average.
According to the FOX Forecast Center, Salt Lake City is currently reporting just 0.1 inches of snow for the season, which is nearly 33 inches below its seasonal average to date.
(FOX Weather)
As the weather pattern changes, many of these mountain ranges are expected to see beneficial snowfall over the next 10 days.
