The arrival of wintry conditions in the Wood River Valley early Monday morning may have piqued some curiosity about what the colder months ahead have in store.
Though the National Oceanic and Atmospheric Administration’s more detailed U.S. Winter Outlook is still a week out from publication, its long-range winter forecast issued on Sept. 16 may provide some clues.
According to the agency’s preliminary September report, there’s a 33% to 40% chance that south-central Idaho will experience both “above normal” snowfall and “above normal” temperatures from November through February.
“An eastward expansion of enhanced above-normal precipitation probabilities is noted across the northwestern continental United States,” NOAA meteorologist Scott Handel stated.
The agency also predicted a second La Niña year, marked by cooler sea temperatures near the equator of the Pacific Ocean.
During La Niña years, the jet stream tends to meander farther north, steering storm systems from the Pacific into higher-latitude states like Oregon, Idaho, Montana, according to the agency. El Niño, La Niña’s counterpart, warms large areas of the Pacific and tends to push storm tracks farther south.
“A transition from ENSO [neutral sea surface temperatures] to La Niña is favored in the next couple of months, with a 70%-80% chance of La Niña during the Northern Hemisphere winter,” NOAA stated on Sept. 16. “It’s looking more probable that La Niña will lock in by this winter.”
Commercial weather forecasting service AccuWeather also released a long-range winter outlook on Sept. 29, predicting “some similarities this year compared to last winter” but a weaker overall La Niña pattern.
“A wet winter is still anticipated with plenty of snow in the mountains, but it might not total as much as last winter, and more breaks in the stormy pattern are projected,” AccuWeather stated. “Still, there will be enough precipitation to lay down a healthy snowpack for ski resorts across the Pacific Northwest and the northern Rocky Mountains.”
A weaker La Niña could result in fewer storms but a potentially weaker polar vortex and an influx of arctic air into the Northwest, according to the service.
“La Niña may not come and do the same things that we typically see,” AccuWeather Senior Meteorologist Paul Pastelok stated.
Storm slams Sawtooths, Big Lost Range
The storm that delivered about 6 inches of fresh powder on Baldy early Monday morning was part of a larger east-tracking system created by a band of cold air from the Pacific and moisture from the Gulf of Mexico, according to AccuWeather. While the system brought damaging winds into California and Nevada—along with red flag warnings and power shutoffs—the snow it delivered in the Rockies inspired some resorts to fire up their snow guns and celebrate.
Jackson Hole Mountain Resort in Wyoming, and Utah’s Snowbird and Alta ski areas were the real winners among Western resorts this weekend, each receiving between 12 and 18 inches of snow, according to the National Weather Service. Colorado’s Arapahoe Basin Ski Area and Montana’s Big Sky Resort received about 6 inches, as did Idaho’s Soldier Mountain and Magic Mountain resorts.
Locally, the National Weather Service reported snow accumulations of 4 to 6 inches in Ketchum, 4 inches in Sun Valley and Stanley, 3 to 4 inches out East Fork, 2 inches in Gimlet and 1 inch in Hailey and Bellevue. Other areas, like Trail Creek Summit and Galena Summit, received about a foot of snow, while Redfish Lake and parts of the Sawtooths received 18 inches. The drought-stricken Big Lost Range, including Leatherman Peak, received a whopping 36 inches, according to a weekend snowfall analysis by the National Weather Service.
The weekend snow also helped saturate the ground and douse hot spots in the Salmon-Challis National Forest, where the Boundary Fire—now nearly contained—has spread across nearly 88,000 acres.