textproduct: Salt Lake City

KEY MESSAGES

- A series of storms will impact the region through Saturday morning. The first storm will bring a strong cold front through much of Utah tonight into Thursday morning, bringing snow levels to valley floors across northern and western Utah.

- Periods of snow will occur during the Thursday morning commute across the Wasatch Front, primarily east of I-15.

- Another round of snow will impact Thursday afternoon through Saturday morning, with the heaviest accumulations centered on the higher elevations.

- Dry and mild conditions will return for the upcoming weekend.

DISCUSSION

A complex scenario will unfold across the region over the next several days, bringing periods of accumulating snow for much of the state through at least Friday evening.

Early afternoon satellite and upper air analysis indicates a trough is shifting into the western United States. The associated upper level low is currently approaching the Pacific Coast.

There is a significant variability in potential outcomes with the first portion of this system through Thursday morning. With multiple vorticity centers embedded within the main trough, ensemble members are showing a wide variation in the location of the resulting upper level lows by Thursday morning. Consensus suggestions that as the cold front crosses into northern Utah, some portion of the boundary will be undergoing frontolysis as the forcing shifts northeast into Wyoming. Exactly how far south this occurs is one point of variation.

The most likely outcome is north of Odgen to the Idaho border, the front will come in strong but will weaken quickly, with lighter precipitation amounts ending prior to the bulk of the Thursday morning commute. Whereas south of Ogden, the front will remain sufficiently strong to continue to bring periods of snow through the Thursday morning commute, though the most probable location for winter driving conditions will remain east of I-15.

After a period of subsidence later Thursday morning into early Thursday afternoon, the next phase of this system will shift into the region. Again, there is broad variance in the ensemble systems in how northwesterly the 700mb flow will be (and thus how heavy the snow will be for the Wasatch Thursday evening into Friday), as well as how long precipitation will last into Friday.

The most probable outcome is periods of snow showers will continue through much of the region through the night Thursday and into Friday morning. There is an approximately 20% chance Wasatch valley floors will see accumulating snow during the Friday morning rush hour period, 40% for benches.

Given lack of confidence in seeing warning amounts in the mountains (less than 20% chance for most of the Wasatch, around 40% chance for the upper Cottonwoods), issued winter weather advisories rather than upgrading to warnings in the areas covered by the Winter Storm Watch. Continued going advisories, though snow totals were lowered based on current trends.

For the Wasatch Front, based on coordination with transportation partners, amounts and impacts remained too limited to issue a winter weather advisory, but this will need to be monitored over the next 12 hours.

REST OF UTAH AND SOUTHWEST WYOMING

South winds are expected at most sites through the afternoon ahead of a cold front which will bring a northwest wind shift to most sites tonight. Snow is forecast at most locations across central and northern UT and southwest WY tonight into the day on Thursday along with MVFR ceilings. Ceilings could rise to VFR by late Thursday morning at some locations as the front moves further east and precipitation becomes more scattered.

SLC WATCHES/WARNINGS/ADVISORIES

UT...Winter Weather Advisory from 2 AM Thursday to 5 PM MST Friday for UTZ108-110>112-117.

Winter Weather Advisory from 5 AM Thursday to 5 PM MST Friday for UTZ113-118-119-125.

WY...Winter Weather Advisory from 2 AM Thursday to 5 PM MST Friday for WYZ021.