St. Cloud, MN Weather Forecast

Major El Nino This Winter Means.....

Meteorological summer began on June 1 and the June solstice, the longest day of the year in Minnesota, will occur on Sunday. Last week, however, the National Weather Service's Climate Prediction Center updated its forecast of a strong El Nino event coming this winter.

As you probably recall from news sources or previous discussions, El Nino produces unusually warm water in the eastern portion of the tropical Pacific ocean. Since the basic driving force of the jet stream is large-scale temperature differences, a reversal of the normal temperature trend in the tropical Pacific would have effects on the overall weather pattern. This tends to produce a shift in the wintertime storm track, with one branch shifting southward to the eastern Pacific off the Mexico or California coast. That tends to produce frequent precipitation either over the Southwestern US or along the Gulf Coast. The more northern storm track, which separates milder air from the coldest air in the Northern Hemisphere, tends to lock up in Canada (scroll down to see North America flow pattern). So, the odds would favor a milder than average winter from the Canadian Prairies through the northern Plains including Minnesota.

What the alerts don't tell is that there have been relatively few El Ninos in the past (around 10) with few strong ones (less than 10). And, not every El Nino cold season has produced a milder than average winter in Minnesota, although having much milder than average temperature change off Central America makes the chances better.

Chances Better Than Average for a Mild Winter, But Not Guaranteed

So, how do I interpret the possibilities? I'll say the average temperature for any winter has 8 chances: two of those chances would produce a winter cold enough that we would notice, two of those chances would produce a mild enough winter that we would notice, and the remain four chances would produce a winter only a bit cooler or warmer than average. The presence of an El Nino would change these odds. This winter, perhaps there would only be one chance for a significantly colder than average winter and 3 chances for a much milder than average winter. 4 of the chances would still be having a winter closer to average temperature. A strong El Nino would give us 4 chances for a mild winter and 3 chances for an average winter. Still, a surprise of a cold winter is not out of the question.

Snowfall and Precipitation More Uncertain

The relationship of winter temperatures in the Northern Plains to having an El Nino is a good one. However, the winter snowfall is much more uncertain. The presence of two storm tracks means that it is possible that storms tend to Minnesota, leading to low precipitation. On the other hand, there may be times that the storm tracks work together to produce a really strong storm. And, with the southern storm track pushing Gulf of Mexico moisture further northward, a really strong Central US storm could have much more moisture than usual. In 2023-2024, we had a strong El Nino, but with an usual amount of strong storms. That ended up producing the 5th wettest winter and the wettest December in St. Cloud records. However, the frequent presence of warm air in these storms often gave Minnesota mixed precipitation or even rain, so the 2023-2024 snowfall total was low (31.9 inches, the lowest of our recent low snowfall winters). But, a small movement of the warm air southward could have put central Minnesota on the snowier side.

There is also a second possibility to get storms during an El Nino season. The northern storm track could produce a strong storm. Even though the cold may be marginal, it could be cold enough to produce snow.

Even a Mild Winter Can Get Really Cold or Snowy At Times

So, the presence of El Nino really gives us very little information about how much precipitation we will see and how much of it will be snow. Even during the El Nino season of 2023-2024, we had a week in March with 18.2 inches of snow, producing the 8th snowiest March in St. Cloud records. And, that January, we had two complete days when the temperature never got higher than 0. All of that occurred during a mild and relatively snowless winter.

Finally, predictions of an El Nino doesn't guarantee an El Nino happens.

Forecasts of Global Warming Weight the Odds, But Do Not Rule Out Cold Seasons

We should take the predictions of global warming in the same manner as the El Nino prediction. The odds for a cold winter in a globally warmed atmosphere would be about the same as during a strong El Nino season: 1 chance of 8 for a colder than average winter, 3 chances of 8 for a near average winter, and 4 chances of 8 for a warmer than average winter. Less than 1 of those 8 chances would be for a record-setting warm year, but the chance would be higher than during the current climate. Since the forecasts only deal with average temperatures, there is less information about how wet or dry we could be. The conclusion of more cold season precipitation at northern latitudes comes from milder air having a chance to carry more moisture than colder air. The storm track could be closer to us than usual, since the place where warm and cold come together could be further north, but that doesn't count how it would set up for any given period of time. 

Showers and Thunderstorms Today...Most Likely This AM

Getting back to summer, we have a pattern favorable for showers and thunderstorms today. Some of those storms have been moving from south central Canada and the Dakotas through Minnesota overnight (see College of DuPage north central US radar loop). That chance will continue as the storm system in Alberta (see some counterclockwise rotation on the College of DuPage North America mid-level water vapor loop) approaches. The storms were produced by the much warmer air in the western High Plains (highs in the 80's and 90's in western South Dakota and Nebraska on the NWS WPC Tuesday 4 PM CDT North America zoom-in map) being pulled over the cooler air in southern Alberta, Saskatchewan, and the Dakotas. This bunch of showers and thunderstorms will continue into the morning hours (although they may concentrate in southern and parts of central Minnesota, based on the overnight movement).

Scattered PM Storms

The morning storms will still have a chance to produce straight-line damaging winds, with the main threat in Iowa, but southeastern Minnesota may catch a part of the severe activity. This afternoon, an area to the south and east of the morning activity has a good chance for severe weather (category 4 of 5), especially from Missouri through Illinois, Indiana, and into Ohio.

In central Minnesota, there will be a chance of some scattered showers and thunderstorms, but the bulk of the rain (see Day 1 of the NWS WPC quantitative precipitation forecast) and the severe weather will be well to our south and east. 

Next Rain Chance Friday

A weaker storm system will push into Minnesota on Friday. There won't be as much lift as with today's system, and the storm will have relatively poor timing, with the best chance for showers late at night or during the morning. So, the rainfall potential will be smaller (see Day 3 of the NWS WPC quantitative precipitation forecast).

Coolest Temperatures Today into Saturday Morning, Some Weekend Moderation

We will continue with the cooler than average temperatures. Today and tomorrow, high temperatures will struggle to get to 70 degrees. Highs will generally return to the 70's over the weekend, but low temperatures on a clear night will dip into the 40's (most likely Thursday and Friday nights).

Uncertain Shower Chances (Sunday? Early Next Week?)

There will continue to be a parade of weather systems moving from the eastern Pacific through the West and into the Plains states. The next system, due Sunday, is very uncertain since the computer forecasts differ by at least a state about the precipitation. All of the forecasts show the main chance of showers and thunderstorms to our south (see Days 4-5 of the NWS WPC quantitative precipitation forecast), but I wouldn't trust this forecast yet.

And, the forecast of frequent systems continues into early next week, so there would be uncertain chances for rain. At this point, the high temperature forecasts don't appear to be as cool as what we have seen. However, that's a shaky forecast for now.