As we look at global weather patterns and how the jet stream affects weather across the US, the end of El Niño and the beginning of La Ninã tells —potentially— a very different story from last years winter.
Here’s a Link to CNN’s Reporting on this Topic
What is La Niña?
La Niña is a natural climate pattern characterized by cooler than average ocean temperatures in the equatorial Pacific. It influences global weather patterns, with its effects being most pronounced during winter months in the Northern Hemisphere. La Niña is expected to develop this fall and influence temperatures, precipitation, and snowfall across the United States. It typically causes a northward shift in the jet stream, which can lead to changes in temperature and precipitation patterns, particularly affecting winter weather in the US.
How Will this Effect US Snowfall and Ice Dams for the 2025 winter season?
The effects of La Niña have different potential outcomes for regions of the US that typically encounter snow and ice —those regions can be divided as follows:
The Pacific Northwest
Expecting wetter and cooler air than normal, resulting in potentially more snowfall. This differs significantly from the El Niño phase of the cycle of last winter, where drier and warmer air persisted. Cooler and wetter air make form basis for a high potential for ice dam activity in the Pacific Northwest.
The South
Expecting drier and warmer weather than normal. Compared to last winter, the wetter air is pushed higher into the northern hemisphere, leaving drier air across the south. Warmer, drier air could mean less potential for ice dams than last year across the south.
The Midwest & Interior-Northeast
Expecting more precipitation than normal, and cooler temperatures than normal. This differs significantly from the El Niño phase of the cycle of last winter, where drier and warmer air persisted. Cooler and wetter air make form basis for a high potential for ice dam activity in the Midwest and Interior-Northeast.
The Northeast
Wetter than normal, however potentially warmer than normal as well. So where higher precipitation is predicted, this could be manifested as snow or rainfall if the temperatures creep up above freezing. Ice dam activity for this region is harder to predict. If temperatures create a freeze-thaw-refreeze cycle in combination of a decent amount of snow, the results could be significant regarding the formation of ice dams. If the weather creates longer, persistent periods of warmer temperatures, even when wet, ice dams could fail to thrive.
The Uncertainty of the Niño-Niña Pattern
It’s important to note that predictions surrounding weather patters and the impact of El Niño and La Niña are just that: predictions. Additionally the strength of the pattern is also a factor that can determine potentials for ice dams and snowfall in general. Meteorologists use sophisticated weather models to try and identify potential outcomes, but things shift over time making it impossible to be highly accurate.
Comparing the Coming Winter with Last Season, Based on the El Niño – La Niña Pattern
You can see that the weather patters represent a potential complete flip of what occurred last year. Where it was wetter and cooler to the south, this year is predicted to be drier and warmer. Similarly to the north, where it was Warner and drier is now predicted to be wetter and cooler.
