textproduct: Salt Lake City

KEY MESSAGES

- A cold frontal boundary will push through Utah through the overnight hours, bringing an area of enhanced mixed precipitation to northern Utah through this evening. Light snow accumulations will be possible for the lower elevation valleys.

- Temperatures will drop to near or below seasonal normals on Sunday, warming back to above normal levels through the first half of the upcoming week.

- There is potential for a late week storm to bring valley rain and mountain snow across Utah from late Thursday through Saturday, however, there still exists great uncertainty at this point in time.

DISCUSSION

Through the remainder of the evening and overnight hours, a trailing shortwave trough will push a reinforcing cold frontal boundary across the forecast area which will enhance an area of light to moderate mountain snowfall and mixed valley precipitation. For northern Utah, this boundary is expected to clear the area by midnight, meaning that between now and then will be the period to accumulate much of any snowfall for both mountains and valleys. As of writing this, temperatures along the Wasatch Front are far too warm to support snowfall to the valley floors, however, as the sun sets and the colder airmass becomes more established across the area, temperatures will become cold enough to support snowfall on the back end of the boundary. The biggest limiting factor to see appreciable snowfall in the lower elevation valleys will be the lack of moisture in the post- frontal environment. A few hi-res models do support lake enhanced snow showers in the Salt Lake Valley during the overnight hours, however, both the decreasing moisture and rapidly stabilizing conditions in the wake of the front will make it difficult to achieve this. That said, still expecting around a 15-20% chance of light snow accumulations (less than 0.5 inches) in the southern half of the Salt Lake Valley overnight.

Additionally, as the aforementioned frontal boundary progress across the region, a brief period of breezy winds are expected (20-30 mph wind gusts). Areas likely to exceed the 30 mph threshold will be in the western Uinta Basin and near Fremont Junction on I-70 where wave breaking over the upstream terrain may lead to wind gusts in excess of 45 mph for 1-3 hours. Confidence in this occurring is not high enough to issue any headlines for wind and impacts should be quite limited given the timing of the frontal passage.

In the post-frontal environment, Sunday will begin partly cloudy (mainly confined to terrain features) and clear throughout the morning hours as the drier air spreads southward. In general, expecting a day full of sunshine and near normal temperatures (finally) across the forecast area.

High pressure will reestablish across the forecast area through the upcoming week, with overhead temperatures warming fairly rapidly by the middle of the week. As such, expecting valley inversions to develop across Utah alongside a stout warming trend for the higher elevations. While valley areas will gradually warm throughout the week, intensifying inversions will make it difficult to achieve the full potential of the airmass. Nonetheless, high temperatures are expected to rise back to above normal levels by as early as Monday, then upwards of 10-15 degrees above normal by Wednesday/ Thursday.

By late in the week our next potential storm system will begin to push into the forecast area if all goes according to ensemble means. There is still a considerable amount of uncertainty to work through with this next potential system as modeled 10th to 90th percentile for the mountainous terrain ranges from quite literally nothing to upwards of 1.5 to 2 inches of snow-water equivalent. The most probable solution (50-60% chance) is that this system progresses into the region by late Thursday and spreads moisture across a majority of the Utah mountains. Given the very warm antecedent conditions and relatively warm system (stemming from the subtropical Pacific), snow levels are expected to remain above valley floors. More to come on this throughout the week, but for now the biggest takeaway is that the system will be warm and will limit any snowfall to the higher elevations.

REST OF UTAH AND SOUTHWEST WYOMING

Rain/snow showers across northern Utah and southwest Wyoming will temporarily reduce CIGS/VIS into the MVFR range through 04Z, with brief and localized IFR conditions possible. VFR conditions will follow for the remainder of the evening and overnight hours, with the exception to areas south of the Great Salt Lake near KTVY where snow showers with IFR/LIFR conditions will remain possible overnight.

SLC WATCHES/WARNINGS/ADVISORIES

UT...Winter Weather Advisory until 5 AM MST Sunday for UTZ110>113.

Winter Weather Advisory until 5 PM MST this afternoon for UTZ117- 125.

WY...None.