textproduct: Salt Lake City

KEY MESSAGES

- A warm, moisture rich storm will continue valley rain and mountain snow through Monday. The heaviest precipitation is anticipated late tonight through Monday morning across most Utah mountains, particularly those that do well in southwesterly flow, resulting in travel impacts for mountain routes.

- After a relative lull Tuesday, a pair of colder systems will impact the area late Wednesday into early Friday, bringing the potential for accumulating snow to the northern valleys, as well as significant mountain snow accumulations.

LONG TERM (After 12Z/5AM Tuesday)

Although conditions will remain modestly active through the work week, snow totals have come down slightly (including in the valleys) given a trend towards precipitation ending earlier on Friday as strong subsidence takes over.

At the start of the long-term period on Tuesday, expect light orographic showers across mainly the northern mountains, with minimal snow accumulations, if any. As zonal flow gradually becomes more cyclonic and modest low- to mid-level moisture pushes into the region, PoPs will increase through the day on Wednesday. A subtle shortwave trough will further enhance precipitation coverage and QPF as it crosses the state Wednesday afternoon. During this period, snow levels will hover around 4500ft near the UT-ID border up to 6000ft along the UT-AZ border.

By Thursday, a stronger shortwave trough will swing through the region, with an associated cold front bringing much colder air to the forecast area between roughly Thursday afternoon and Friday morning. Snow levels will drop below valley floors by Thursday afternoon at the latest. Despite appreciable dynamics associated with this system, moisture will likely be the limiting factor regarding snow amounts, though more localized effects such as orographic enhancement and/or lake-effect off of the Great Salt Lake could bump up these amounts. Local lake-effect guidance suggests a 60% chance of lake-effect developing Thursday night in the Salt Lake Valley. In this post-frontal period, areas favored in northwest flow are likely to benefit, given lingering low-level moisture, at least through Thursday night. However, the length of this period will really depend on how long subsidence holds off heading into Friday morning. Model guidance has trended towards precipitation ending earlier, which could further limit both mountain and valley snow amounts.

NBM probabilities of greater than 1" of snow have decreased along the Wasatch Front, only around 30% for valley floors and 60-80% for benches. Chances for >6" of snow are down to around 20-50% across the Wasatch Back (higher end near Park City). In the mountains, while the higher end amounts have decreased, 25th-75th percentile spread is still fairly wide, around 10-20" of snow for the Upper Cottonwoods and Bear Rivers (lower amounts elsewhere) and T-6" in the southern mountains (namely areas near Brian Head and in the Tushars). Snow ratios will be quite high, especially compared to recent storms, given the cold air mass moving into the region.

Temperatures at 700-mb will drop from around -7C on Wednesday down to around -14C to -16C by Friday, resulting in colder surface temperatures heading into the weekend as cloud cover clears. Forecast lows will dive down to the upper-teens/low-20s across most low elevation valleys, low-teens/single digits across the Wasatch Back, and even below freezing down in St. George. Additionally, given high confidence in strong subsidence moving into the region as ridging builds over the west coast, valley inversions are likely to develop...potentially more quickly if valleys have recent snow cover.

REST OF UTAH AND SOUTHWEST WYOMING

An impulse and associated moisture embedded in deep southwesterly to westerly flow will bring unsettled weather to area terminals, especially northern. Widespread BKN to OVC VFR cloud cover ~6-10 kft will blanket the area, with lower CIGS noted during times of precipitation. Around a 30-50% chance of MVFR conditions are noted with rain, with those probabilities more reflective of IFR conds at terminals where precip switches to snow. Snow levels will start around 7-8 kft, and falling to around 6-7 kft overnight into early Monday. Highest precip chances noted from roughly around 03Z to 22Z Mon.

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SLC WATCHES/WARNINGS/ADVISORIES

UT...Winter Weather Advisory until 11 PM MST Monday for UTZ110>112.

Winter Weather Advisory until 11 PM MST Monday for UTZ113.

Winter Weather Advisory until 2 PM MST Monday for UTZ125.

WY...None.