SALT LAKE CITY — Many Utahns could wake up to a white Christmas this year — or at least cleaner air.

A small storm is expected to accompany Santa as he passes through the state between late Christmas Eve and early Christmas Day. However, the forecast precipitation amounts are not particularly impressive, but the system has a good chance of at least some measurable precipitation, favoring parts of central and southern Utah.

Storm timing

The projected system follows another small system that moved through the northern half of Utah on Monday, delivering 0.20 inches or more of precipitation around Ogden and north, including up to 0.37 inches of rain in Brigham City. The storm hit Salt Lake City and caused some showers there as well.

However, it did little to keep the air clean.

Johnson explains that the storm was not very “dynamic” because there was not enough cold air to push out a high-pressure system that has dominated Utah’s weather pattern since last week, and not enough wind to support the Wasatch Front’s recent reversal eliminate. Instead, the storm encountered the high pressure system and weakened as it crossed Utah.

“We cleaned the air up in Ogden a little bit … but it still hasn’t changed,” he said.

The next system aims to deliver a gift of air quality while ensuring a white Christmas. It is expected to come from the west and possibly split in two as it is expected to reach Utah after 9 p.m. on Christmas Eve. A mix of rain and snow is forecast for most of the state, lasting into Christmas morning – where the rain is expected to transition to snow – before the system dissipates later in the day.

Who gets a white Christmas?

The approaching storm could bring nearly a foot of snow to places like Brian Head and Alta, but low-lying areas could also get snow.

The National Weather Service updated its snow probability models Monday morning, giving many areas in Utah a 25-60% chance of getting at least 0.1 inches of snow over the next few days. Aside from the mountains, Beaver has the highest probability at 58%; St. George, no surprise, has the lowest probability overall.

Johnson said he would give the Wasatch Front more of a 20-40 percent chance of at least 0.1 inches just because it is a relatively warm storm for late December and the southern half of the two-part system is often stronger. The weather service notes that communities in southwest and central Utah such as Beaver, Cedar City, Ephraim and Richfield have the highest chance (between 15 and 31%) of at least 2 inches of snow falling by early Thursday.

How much precipitation persists as the system enters Utah and when the rain transitions to snow will likely determine how much snow communities receive, Johnson adds. Weather service forecasters note that some models are also split between two “equally likely” storm track scenarios, one of which would bring more moisture to northern Utah. This would increase the chance of snow in low lying areas.

At least for Salt Lake City, measurable fresh snow would be a rarity. The National Weather Service has tracked the city’s White Christmases since 1952 using various definitions. If Utah’s capital city receives 0.1 inches on Wednesday, it would be the first white Christmas since 2019 – based on the definition of at least 0.1 inches of snow on the holiday. This has only happened eleven times in the last 72 years.

The other definition of white Christmas is snow on the ground before Christmas Day, which is more common in Utah’s capital city. On Christmas Day two years ago there were still 5cm on the ground; Since 1952, there have been at least an inch on the ground 35 other times.

More will follow

While most of the deep snow will likely melt by the end of the holiday season, Johnson said some disorganized persistent waves of moisture are expected to move through the state by the end of the week. These, he said, could create a “nice touch of moisture” in the mountains.

These waves will also likely produce some additional rain and snow showers in the valleys. Warmer and possibly drier conditions are forecast for the final weekend of the year.

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