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Breezy and relatively warm in the Salt Lake Valley this morning. Temperatures actually bottomed out near midnight last night before clouds moved over and winds kicked up out of the south. A low of 36 F was recorded at KSLC just after 12AM 12/17/2025 before winds increased and temperatures rose by about 12 degrees by 6AM. 

Observations from KSLC 12/16-12/17/2025 Top: Temperature, RH, and dew pt; Bottom: wind speed, gust, and direction

Typically, nights are coldest when skies are clear and winds are calm. The lack of winds and clouds allows the most efficient conditions for nighttime radiative cooling, where the Earth's surface loses heat by emitting  thermal infrared energy (longwave radiation) upward into space. This allows the surface to cool faster than the air directly above it, creating a nocturnal temperature inversion. 

Nighttime temps with calm winds and clear skies (Credit: NWS)

On nights when there is sufficient wind, the warmer air from above the surface and cooler air near the surface are mixed, which has the net affect of warming the air near the surface. This process is similar to a fan in a room mixing warmer air near the ceiling down to the ground. Clouds act as another layer to inhibit nighttime cooling due to the fact that clouds radiate infrared energy towards the surface.

Nighttime surfaces temps with breezy winds and clear skies (Credit: NWS)

Today 12/17/2025

A decaying atmospheric river currently impacting northern Utah, bringing strong winds and precipitation through the afternoon hours. The main upper-level low associated with this storm is centered across the northern and Canadian Rockies as evidenced in the mid-level water vapor imagery below. 

GOES-18 West 12/17/2025

A strong jet maximum and coincident tight surface pressure gradient has already brought strong southerly to westerly winds this afternoon, with gusts 60-70+ mph observed, particularly across the West Desert. Winds were strong enough to create a brief window of blowing dust that swept across the SL Valley prior to the arrival of a band of moderate to heavy rainfall. 

Blowing dust moving across downtown SLC 12/17/2025. Camera image is looking west across downtown. 

Mosaic radar loop 1830-2150Z

The heaviest and most consistent showers have already come to an end in the SL Valley, but will continue over course of the afternoon in the mountains. A few sloppy inches of snow are possible above 8000', with less possible at the tail end of the storm between 7000-8000' as cooler air moves in and snow levels drop. Not much...

Another possible system this weekend. But once again, it looks to be a 'warm' storm and any substantial precipitation amounts may be hit or miss across northern Utah.