Why weather service says Utah may be in line for another wet winter

SALT LAKE CITY — Utah could be looking at another moist winter even with a shift in oceanic patterns in play, according to a newly released long-range outlook, which would be good news for the state’s water situation and ski resorts if it comes to fruition.

The outlook, released by the National Weather Service’s Climate Prediction Center on Thursday, projects a 33% to 40% probability Utah will experience above-normal precipitation during December, January, and February, the three months that compose meteorological winter.

Only a section of northernmost Utah is listed as being in “equal chances,” meaning there are no indications leaning toward either a wetter, drier, or normal winter in terms of precipitation. It’s an improvement from most of the center’s other recent reports, which had listed all of Utah in equal chances.

These maps show the projected winter outlook for the U.S. Utah is forecast to have a greater probability for above-normal precipitation during the season. (National Weather Service Climate Prediction Center)

The outlook lists most of Utah as having equal chances when it comes to temperatures, aside from a section of northwest Utah, which has about 33% to 40% odds of above-normal temperatures. In all, the prediction center projects drought will only persist in a sliver of eastern parts of the state between now and the end of January 2024.

This doesn’t guarantee it will be a wet winter, but federal forecasters say trends lean slightly toward above-normal precipitation based on what’s expected and historic trends. Seth Warthen, a National Weather Service meteorologist in its Salt Lake City office, adds the odds of a repeat of last winter — where Utah ended up with a record 30-inch statewide snowpack — are also unlikely.

However, even a normal year can be beneficial. Salt Lake City, for example, normally receives 4.13 inches of precipitation over the three-month span, according to weather service data. Alta, in the Wasatch Mountains, has averaged more than 20 inches of precipitation since 2000, per the agency’s available data.

This map shows the U.S. drought outlook from Thursday through the end of January 2024. (National Weather Service Climate Prediction Center)

The agency’s outlook comes after Utah wrapped up its 17th-wettest water year since 1895 at the end of September, according to National Centers for Environmental Information data. That record 30-inch statewide snowpack over last winter and early spring is a big reason for the success of the water year, helping the state’s reservoir system reach 86% capacity at its peak this year — 25 percentage points ahead of the 2022 peak.

And given the state’s higher soil moisture levels, there’s a greater probability that any snowpack collected in the mountains efficiently melts into the state’s streams and rivers before flowing into any reservoirs.

“A lot of reservoirs are in much better shape this year than they were last year … but in order to get recharge into the Great Salt Lake and a number of those larger reservoirs, you’re going to need to continue to have good winters,” Warthen told KSL.com. “That extra water would certainly be helpful for some of those (larger) reservoirs to be filled.”

What’s driving this year’s outlook?

Federal forecasters previously issued an advisory stating there’s an 80% chance an El Niño oceanic pattern will linger into spring 2024. That’s on top of a 75% to 85% chance that there’s a strong El Niño pattern and about a 1 in 3 probability it’s the strongest on record. A La Niña pattern existed over the previous three winters.

While Utah generally isn’t impacted much by either pattern, Warthen explains a stronger El Niño typically produces an “amplified” Pacific jetstream that increases the odds of active patterns flowing into the West.

The position of this jetstream will ultimately determine how much snow Utah gets — and what areas of the state receive the most snow.

Last winter, the La Niña jetstream ended lower than usual, resulting in most Pacific storms ending up in Utah and the record snowfall. An El Niño pattern tends to favor southern Utah; however, the whole state may benefit if ends up slightly north than it historically does this winter. Conversely, Utah may lose out on moisture if it sets up slightly more south than normal.

“Subtle shifts in the location of how these low-pressure systems set up and how that jetstream sets up are going to have the biggest impacts on whether this El Niño will actually result in a wetter-than-normal winter,” he said. “Overall, looking at that week-to-week weather and where that jetstream sets up and how active the storm track is — that’s going to be the big thing.”

What about the rest of the U.S.?

El Niño is forecast to produce differing winter experiences throughout the country.

Drier-than-normal conditions are forecast for parts of the Pacific Northwest and most of the northern Great Plains, while above-normal precipitation is more likely throughout the American Southwest, lower Great Plains, and the Southeast.

“An enhanced southern jet stream and associated moisture often present during strong El Niño events supports high odds for above-average precipitation for the Gulf Coast, lower Mississippi Valley and Southeast states this winter,” said Jon Gottschalck, the Climate Prediction Center’s Operational Prediction Branch chief, in a statement.

The Pacific Coast and Pacific Northwest, the northern Great Plains, and the Northeast are also all listed as having greater probabilities for above-normal temperatures, while the rest of the contiguous U.S. is listed as either having normal or equal chances when it comes to temperature.