Winter storm warnings issued across Utah ahead of incoming atmospheric river

SALT LAKE CITY — After a few overperforming systems that benefitted Utah's northern half, an incoming atmospheric river is slated to blast all of the state's regions with potentially heavy moisture.

The National Weather Service issued a series of winter storm warnings and winter weather advisories across Utah, which note that 10-24 inches of snow is possible across the state's mountain range between Thursday morning and Saturday afternoon. Some areas could end up with closer to 3 feet of snow. Some valley communities could also receive multiple inches of snow.

KSL meteorologist Matt Johnson says the incoming storm will "easily" be the biggest one to impact southern Utah this year, likely breaking dry spells that have lasted months in some parts of the region.

"(It has) great water content from north to south," he said. "It's not going to turn the season around in southern Utah, but at least it's something.

Storm timing

Utah's northern half received a welcomed bump from storms that exceeded expectations over the past few days. Alta was the biggest winner, recording more than 2 feet of new snow since Friday. Valleys also got a decent amount of snow.

The next wave figures to be more substantial and more widespread. A low-pressure system brewing off the Pacific Coast on Wednesday is helping pump "very dense, warm" subtropical air into the Western U.S. It will make its way to Utah as the atmospheric river decays, Johnson explains.

The moisture is forecast to arrive in the mountains by late Thursday morning before expanding across the state in the afternoon. It may start as valley snow in most of Utah's valleys as it mixes in with cold Canadian air that entered the state earlier this week, but a warm front will ultimately help valley precipitation transition to rain.

Johnson says the "brunt of the storm" will likely pass through late Thursday and early Friday. A mix of valley rain and mountain snow is forecast to persist through most of Friday while lingering scattered showers are possible on Saturday — especially in the mountains — before it clears out by the end of the weekend.

Projected accumulations and impacts

Most of the National Weather Service warnings go into effect as early as 11 a.m. Thursday and last through Saturday afternoon in some cases. Those state:

• 1-2 feet of snow is possible for the Wasatch, west Uinta and central mountain ranges. Totals of 3 feet or more are possible in areas like the upper Cottonwood canyons and the Bear River Range.
• 10-20 inches of snow is possible for the southwest mountains. Higher totals closer to 3 feet are possible near Brian Head, as well as the Pine Valley and Tushar mountain ranges.
• 1-2 feet of snow is possible in the La Sal and Abajo Mountains in southeastern Utah.
• 8-14 inches of snow is possible across the Wasatch Back; totals closer to 18 inches are possible in the Park City area.

Winter weather advisories were also issued for communities across the state:

• A trace to 3 inches of snow is forecast for most of the Wasatch Front and northern Utah. Bench areas might see up to 6 inches by Friday night.
• 2-8 inches for higher-elevation communities in central and south-central Utah like Bryce Canyon, Castle Dale, Panguitch and Price.

Johnson said final totals will likely depend on various factors, including what the snow line ends up being. He adds that some additional snow is possible toward the back end of the storm.

Overall, he said most valleys could receive 0.5-1 inches of precipitation. The storm is also forecast to snap a St. George streak of more than 70 days without measurable precipitation.

The Utah Department of Transportation says drivers should slow down and drive carefully, especially while traveling along mountain passes across the state. Traction laws are likely to be enforced across some mountain passes.

The Utah Avalanche Center issued an avalanche watch as avalanche danger could reach "high" this weekend.

More to come?

The incoming moisture is great news for Utah's snowpack, which has slipped to 78% of its median average statewide. A few smaller storms are expected to pass through Utah's northern half starting early next week, where many basin averages are running above 80% of normal for mid-February.

"I think we can still squeak out an average year in the northern mountains," Johnson said. "Everything is going to lean on March because that's the last snowpack-building month before we hit the apex, and start melting."

The same is less likely for other regions, especially southern Utah. Running totals have fallen below 50% of average across the region's four biggest snowpack basins. Southwestern Utah's basin entered Thursday at 17% of the average after falling into record-low territory on Jan. 20. Extreme drought crept back into southwest Utah last week.

While the incoming storm helps, the region needs "numerous large storms" to get back to normal, Jordan Clayton, a hydrologist with the Natural Resources Conservation Service, wrote in a report earlier this month.

Johnson said the region will likely be skipped by the next storm systems. Long-range outlooks also lean slightly in favor of drier conditions forming over the next three months.

"Something is better than nothing, but does look like a one-and-done deal at least over the next (week)," he said.

Full, seven-day forecasts for areas across Utah can be found online at the KSL Weather Center.

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