Connecting Ag to Climate: Prospects For Drought Relief: What a La Niña Winter Could Mean for WyomingConnecting Ag to Climate:

According to the Wyoming Crop Progress Report from the U.S. Department of Agriculture’s (USDA) National Agricultural Statistics Service (NASS), published Nov. 4, some producers around the state started pulling livestock off of summer pastures early due to rangeland conditions and are starting to supplement with hay. 

In addition, some reported lower hay production, no regrowth on hayed meadows, higher percentages of open cows while pregnancy checking than expected and calves weighing less than usual at weaning. 

While some parts of the state saw moisture in the last couple of weeks, many areas received no measurable rain or snowfall. Looking further ahead, there are many questions about what to expect for precipitation and snowfall to help inform management plans. 

Developing La Niña

As some might have seen in the news, a La Niña is likely to develop sometime this winter. La Niña, which refers to a cooling of surface waters in the tropical Pacific, affects global atmospheric circulation and can influence temperature and precipitation patterns. 

In Wyoming, La Niña events can bring wetter-than-average conditions for parts of the state, hinting at a potentially above-average winter – December through February – for some.

After an extremely dry summer and recent fires, a wet winter would be more than welcome. However, not all La Niña events are equal, and its effects are not the same across the whole state. 

Although not guaranteed, La Niña events generally improve the ability to forecast winter temperature and precipitation trends further out in time, especially strong La Niña events.

If it does form this year – and there’s a better-than-even chance of this happening – a La Niña will be arriving later than expected. This timing lowers the odds of it becoming a strong event, meaning there’s less time for it to shape winter patterns before spring. 

Late-developing La Niña events are somewhat rare, and a weaker one would have less influence on atmospheric patterns overall, reducing predictability and allowing other factors to play a bigger role in shaping winter weather.

What does it mean?

What does a weak La Niña mean for drought relief in Wyoming, considering the current drought and recent wildfires? 

To get a sense of this, we reviewed temperature and precipitation patterns from previous weak La Niña events dating back to 1950. 

The historical analysis suggests a slight tilt toward above-average snowfall in the far northwestern part of the state, while central and eastern areas tend to have near-normal precipitation. For winter temperatures, there is a possibility we could see a colder than normal winter across the entire state.  

It’s important to remember this analysis only shows past outcomes, not the specific causes behind them. In some cases, these patterns might simply reflect the typical conditions we normally expect during a Wyoming winter, rather than the influence of La Niña.

Up in the air

The main takeaway is a weak La Niña will not be as helpful in predicting Wyoming’s winter conditions, compared to a stronger event. 

So, when folks talk about La Niña forming, it’s okay to be a little skeptical. Winter is coming. We hope it will be wet – but not too wet – and we can inch our way out of this drought.

Chad McNutt serves as a climate science and adaptation consultant for Lark Environmental, Inc., where he assesses risks associated with weather and climate trends. Averi Reynolds is an ORISE science communication fellow for the USDA Northern Plains Climate Hub (NPCH), serving Wyoming, Montana, Colorado, Nebraska, South Dakota and North Dakota. The NPCH strives to provide unbiased information about adaptation and mitigation strategies for ranchers, farmers and foresters to help increase their operations’ resilience to weather variability and a changing climate. For more information on the NPCH, visit climatehubs.usda.gov/hubs/northern-plains. The use of corporation names does not constitute an official endorsement or approval by the USDA.