St. Cloud, MN Weather Forecast

The outlook through the weekend continues to be dry, aside from a widely scattered shower this afternoon or Saturday. So, I will spend some time talking about all the hype for the winter of 2026-2027.

Blame It On El Nino

That's because of the prediction that El Nino will develop by the fall (.pdf) and continue through the end of the year. 

How Does El Nino Affect The Winter Storm Track Over North America?

El Nino refers to an usually warm ocean current in the eastern and central tropical Pacific. During an regular cold season, the waters off northern South America (Columbia, Ecuador, Peru) to the Mexican coast tend to be cool, which suppresses thunderstorms in the eastern tropical Pacific. If we replace that cool water with warmer than average water, Northern Hemisphere winter thunderstorms are favored off northwestern South America and Central America.

Those thunderstorms end up helping to favor low pressure systems off the California or Mexican Pacific Coast. This favors a persistent southern branch of the steering winds to be either in California or the Southern Rockies or along the Texas Coast (see third figure down on this NASA El Nino site). There tends to be a second storm track, along the southern boundary of the really cold air, but that frequently sets up to the north of the US from the Pacific Northwest into the Northern Plains. This tends to favor a milder than average winter. This part of the research on El Nino is solid and based on actual processes that affect the steering winds.

Potential Effect on Caribbean, Gulf of Mexico Hurricanes

The outflow from thunderstorms along the Pacific Coast also tends to develop a decent southwest flow over the Gulf of Mexico and the Caribbean Sea. If the El Nino sets up by late summer or early fall, that flow aloft interferes with hurricane development near Central America, since hurricanes require light winds aloft, so that the strong thunderstorms surrounding the eye can drop the central pressure of the storm. That could lead to fewer than average hurricanes developing on the Atlantic side of Central America. It doesn't rule out Atlantic hurricanes that develop in the tropical Atlantic between the Americas and Africa.

Problems: Much of the Link Has to Do With Statistics, Not Weather Processes

The trouble with dealing with El Nino/La Nina is the teleconnections. That's a statistical tool that looks at graphs of Pacific ocean temperatures (above or below average) and compares them with seasonal temperatures departures from average anywhere on the planet. For example, this past winter had a weak La Nina in the eastern tropical Pacific. Minnesota had a near average or slightly milder than average winter, so that would be recorded for this year's event. The teleconnection analysis also links above and below average tropical Pacific water temperatures to areas that are wetter or drier than average.

There are three problems with using these teleconnections:

1. Without a clear theory about why weather patterns would change globally due to temperature changes in the tropical Atlantic, we are left with a correlation without a cause-effect system. For example, this winter had a La Nina and the Vikings finished with a below average record. Does this mean the colder than average water current in the tropical Pacific caused J. J. McCarthy to look lost when playing? You can say a lot of curves have the same shape without one thing causing the other.
2. Even the statistical link is weak when you have few cases. This analysis shows how US temperatures and precipitation are either above average or below average in El Nino and La Nina years. However, note that only 10 years of El Nino and 11 years of La Nina are included. To have confidence in a statistical link, we'd need at least 1000 data points. 
   1. There has been particular attention to the possibility of a strong El Nino event this winter, but there have been only 5 such cases in the data set.
3. This doesn't consider the possibility that there are other circulations set up in other parts of the world that can change the steering wind pattern (the links at this site show the possibility of an Arctic Oscillation, a North Atlantic Oscillation, a Pacific-North America pattern, and a Southern Oscillation).

A Strong El Nino Would Favor a Mild Winter (But Uncertain Snowfall)

As you know, I am not a true believer in long-range forecasts. I do have a bit more confidence in the milder than average winter Minnesota forecast if we get a strong El Nino because there is good theory about how that would shift temperature patterns.

As noted by Kenny Blumenthal of the Minnesota DNR, a strong El Nino still doesn't guarantee either above average snowfall, below average snowfall, or average snowfall for Minnesota. That's because having two storm tracks across North America can sometimes mean that a very strong storm in the southern storm track could track towards the Great Lakes instead of staying along the Gulf Coast. Or the two storm tracks could work together to produce a major Central US storm. In those cases, there would be a good chance that the high moisture air could get pulled well northward from the Gulf of Mexico, creating heavy precipitation. 

Two winters ago, we had a very strong El Nino and below average snowfall (31.9 inches), but a very wet winter. That's because storms from the south did affect Minnesota, but the air was often too warm to support snow. So, I have no confidence in any seasonal snowfall forecast for 2026-2027.

The Forecast Doesn't Guarantee an El Nino

My confidence in a milder than average winter is modest. Note from the NWS Climate Prediction Center El Nino discussion, that the forecasters give a 61 percent chance for an El Nino event to develop this fall. The chance for a strong El Nino is 1 in 4 and the range of possibilities goes from that strong El Nino to actually normal sea surface temperatures. So, the skill in this forecast is quite limited. 

Now back to your regularly-scheduled forecast for the next 7 days....