Back in August, we published our initial Winter Forecast Preview for North America.

After examining the latest ocean-atmosphere signals as of early October, we have made some updates to our winter forecast.

A weak La Niña is now expected for the winter of 2025-2026, but the typical La Niña effects may be counteracted by some other oceanic-atmospheric signals that we are seeing. 

Let's take a look at the latest...

A Weak La Niña Episode is Likely

Back in the summer, the ENSO signal was uncertain, with longer-range projections hinting at roughly equal chances of a La Niña or Neutral winter.

However, based on trends over the past couple of months, confidence is growing that we will experience a weak La Niña winter.

The three-month average Oceanic Niño Index (ONI) from July to September was -0.3ºC, which is already ahead of the same time last year, which ended up being a neutral year as La Niña criteria were not quite met.

For a La Niña episode to officially occur, the ONI must be -0.5ºC or lower for five consecutive three-month overlapping periods. 

NOAA's latest probabilistic outlook has just over a 70% chance of La Nina conditions in early to mid-winter, followed by a likely transition to Neutral conditions by late winter or spring. 

The International Research Institute for Climate & Society's ENSO Model also projects La Nina conditions developing, with a weak episode likely (ONI values between -0.5º and -1.0ºC).

All other factors equal, weak La Niñas tend to favor trough-dominant patterns over the Northwest and West Central U.S., which is typically a good thing for Western ski resorts.

However, stronger oceanic-atmospheric signals in different areas can potentially counteract the ENSO signal in some winters, especially when the ENSO signal is on the weaker side, such as what we are expecting this year. 

As it turns out, we are seeing some signs elsewhere this fall that could potentially counteract the "typical" weak La Nina signal, adding greater uncertainty to the forecast.

Atlantic Ocean Temperature Anomalies

While Pacific Ocean temperatures (including ENSO) are the more obvious connection when it comes to Western U.S. winters, Atlantic Ocean temperatures also have a significant influence on jet stream trends and global weather patterns.

In our August preview, we mentioned a cooling of Atlantic ocean temperatures compared to previous winters, and a connection between the Atlantic Quadpole Mode (AQM), ENSO, and North America winter precipitation that OpenSnow forecaster Luke Stone studied in his Master's thesis work at the University of Utah.

After talking with Luke recently, it appears we are on track for a Neutral AQM winter with colder-than-average North Atlantic temperatures but slightly warmer-than-average ocean temperatures emerging further south in the mid and lower latitudes (which likely precludes a cold AQM from occurring). 

As a result, AQM by itself may not have as much of an influence on ENSO and winter precipitation this year, compared to recent winters when a warm AQM signal (above-average temperatures throughout the Atlantic) had a greater influence.

However, the colder-than-average ocean temperatures in the subpolar region of the North Atlantic, just south of Greenland, could play a significant role in dominant weather patterns across North America this winter.

Cold pools such as this in the North Atlantic have a weakening effect on the Gulf Stream in the Atlantic Ocean (a warm conveyor belt of ocean water that moves from south to north).

This change in typical ocean currents has an atmospheric response that is more likely to cause disruptions to the jet stream and polar vortex, which can lead to trough-dominant patterns and more frequent cold air intrusions into the Eastern U.S. 

When a dip in the jet stream (trough) occurs in the East, this usually coincides with a northward rise in the jet stream and a ridge-dominant pattern somewhere in the West, though the location and magnitude of the ridge can vary. This pattern can favor warmer and drier than normal conditions in some areas of the West.

Quasi-biennial Oscillation (QBO)

The QBO is another signal that influences North American winter weather. Essentially, the QBO refers to upper atmospheric trade wind patterns in the tropics, which in turn have an influence on global weather patterns.

The QBO fluctuates between an easterly and a westerly phase approximately every 13-17 months, and the magnitude of each phase varies from year to year, with stronger magnitude phases having a greater influence on North American weather patterns.

This year, we are heading into a moderate to potentially strong easterly phase of the QBO.

All other factors equal, easterly QBO phases favor more frequent polar vortex disruptions and trough-dominant winter patterns over the East and Central U.S., and ridge-dominant patterns near the West Coast.

Westerly QBO phases, on the other hand, favor a stronger Pacific jet stream (and thus more storms) into Western North America.

In other words, the strong easterly QBO phase expected this year, combined with the cold pool over the North Atlantic, may favor more of a western ridge/eastern trough pattern than we might normally expect in a La Niña winter.

How These Factors Could Interact

Looking back at past years featuring the most similarities to this year between ENSO, QBO, and North Atlantic temperatures, we find that the weak magnitude of La Nina is more often, but not always, counteracted by the other two signals.

However, we've also found a wide range in outcomes from year to year, which makes for a tricky winter forecast (even more so than usual).

Winter 2025-2026 Snowfall Outlook

For the West, there are higher odds of below-average snowfall across California, Oregon, Western Idaho, and portions of Nevada and Arizona. We have found that these areas are most likely to be influenced should a ridge-dominant signal emerge. 

Areas further north in the Pacific Northwest (Washington and Canada) and further east into the Rockies have equal chances of above or below normal snowfall. In some winters, high pressure ridges that remain far enough south and west can keep the door open to more frequent storms across these regions.

In the East, the combination of weak La Nina along with the North Atlantic and QBO signals noted favor higher odds of above-normal snowfall across the Upper Midwest, Great Lakes, and portions of the Mid-Atlantic.

Winter 2025-2026 Temperature Outlook

We are expecting higher odds of above-normal temperatures for most locations west of the Continental Divide, with higher odds of below-normal temperatures across much of Central and Eastern North America.

Areas east of the Divide in Montana and Wyoming, and across the Interior portions of British Columbia and Alberta, have higher odds of below-normal temperatures. 

The Strongest Analog Signals and the Overall Uncertainty

This winter forecast is largely based on what we have seen when evaluating several analog years with the most similarities to this year.

However, there are two past winters we found that are the closest matches to this upcoming winter, featuring 1) a weak La Nina, 2) cold North Atlantic, and 3) strong easterly QBO.

These two winters are 1984-1985 and 2000-2001. 

Interestingly enough, both of these winters were quite different from one another, which speaks to the greater uncertainty of this winter's outlook.

The Winter of 2000-2001

This was a well-below-average winter across much of the West, especially over the Northwest, Northern Rockies, and Sierra. However, the Southwest was the one exception where above-average snowfall occurred (contrary to what is typical during La Niña winters).

This was also a very cold winter across the vast majority of the U.S., except for areas right along the West Coast.

This was also a big snow year for most areas in the East. 

The Winter of 1984-1985

Despite our projection of higher odds of below-average snowfall in some areas, if you're looking for a sign of hope in the West, then this analog year is a good one.

The winter of 1984-1985 featured above-average snowfall across a larger portion of the West with a stronger troughing signal across the Western and Central U.S. compared to the East.

Temperatures were also colder than average across the West and near-average across the East. 

This tells us that, while overall, a colder/snowier East and a warmer/drier California and Oregon are favored when examining all analog seasons... there is also a wide range in possible outcomes, as noted by what occurred in the winter of 1984-1985.

What About the Pacific Blob?

A few weeks ago, we posted an article mentioning the North Pacific Blob, which is a large area of abnormally warm ocean temperatures in Pacific, extending from near the coast of California northward into the Gulf of Alaska.

In the article, we mentioned that the North Pacific Basin as a whole set a record for warm ocean temperatures in August.

We also mentioned that the Pacific Blob is not always a long-duration event, but that the longer it persists, the more likely it is to have an atmospheric impact and favor strong high pressure ridging near the West Coast.

The good news is that the Blob appears to be weakening as of early October. Well-above-average ocean temperatures persist near the California Coast, but we have seen significant cooling in the Gulf of Alaska recently.

So while we are seeing some hints of a possible western ridge/eastern trough setup this winter, it's becoming less likely that a strong blob is going to negatively influence the pattern for Western U.S. skiers this winter, such as what occurred in the poor ski season of 2014-2015.

October Siberian Snow Cover

Another factor that can influence winter weather in North America is October snow cover in Siberia relative to average.

Research from Dr. Judah Cohen at MIT has found that heavy snow cover in Siberia in October is more likely to disrupt the polar vortex, favoring more frequent cold air intrusions into the central U.S. which could in turn favor an eastern trough/western ridge dominant pattern.

So far, it is still uncertain how October snow cover in Siberia may play out this year, as there are mixed signals in the medium to long-range forecast that take us through the end of October.

Final Thoughts

West Coast – Don't panic if you live on the West Coast! 

While our forecast favors a below-average signal over California and Oregon, confidence is lower than usual for this winter due to competing variables at play. Also, the weakening of the blob reduces the potential for a well-below-average winter, so this is also good.

PNW to Rockies – The winter could really go either way across the Rockies, Washington Cascades, and Canada. Based on the past analog years we examined, winters ranged from well above average to near average to well below average, with no clear signals in any direction.

East Coast – If you're an East Coast skier, this outlook should give you reasons for optimism. But at the same time, that doesn't mean that a cold and snowy winter is guaranteed, given the competing factors and lower-than-usual confidence of this outlook.

There are also tons of sub-seasonal weather patterns that cannot be predicted months in advance, and these can potentially throw off a seasonal forecast. 

Keeping Things in Perspective – Regardless of whether or not a winter is above or below average, there are always going to be inter-season patterns that are more or less favorable for snowfall in an area. Even below-average winters will still have good storms and powder days.

Booking a trip 7-10 days in advance and for a general area that looks stormy will increase your chances of scoring the best conditions.

If you're ready to level up your weather app for the upcoming winter season, consider upgrading to OpenSnow All-Access. Whether you’re chasing powder, searching for sunny days, or something in between, our 10-day snow forecasts, expert "Daily Snow" forecasters, and high-resolution weather maps have you covered.

But don't just take my word for it ... "Any weather app can give a mediocre forecast for a mountain town, but only OpenSnow provides a good idea of actual mountain conditions. It's a small price to pay for the best weather forecasts." – Real App Review

---

Download the free OpenSnow app for the most accurate snow forecast and snow report information and stay tuned to our weather forecasts for the latest updates.

Alan Smith