textproduct: Salt Lake City

KEY MESSAGES

- Accumulating snow will continue to impact the higher terrain of central and southern Utah through Tuesday morning.

- Freezing conditions will occur across eastern Box Elder County and several central and southern valley locations tonight and again Tuesday night into Wednesday morning.

- Minor snow accumulations are likely across most valleys across northern/central Utah Thursday evening into Friday morning, potentially impacting the Friday morning commute. Lake-effect snow could locally enhance amounts in the central/northern Wasatch Front

- Very cold temperatures in the wake of this front will bring freezing conditions to most Utah valleys excluding lower Washington County and the communities along the Virgin River near Zion National Park Thursday night into Friday morning and again Friday night into Saturday morning.

DISCUSSION

Widespread showers are ongoing across southern Utah this evening under upper-level diffluence just ahead of the closed low centered over Las Vegas. This low will track eastward across southern Utah overnight, with the main area of precipitation exiting to our east by mid-day Tuesday alongside said low. A weak deformation band, which looked more impressive in prior model runs, could still produce snowfall rates in excess of 1"/hr overnight across the southern mountains. Ongoing Winter Weather Advisories cover this threat well. Despite overall quieter conditions tomorrow, weak, isolated showers may still develop statewide during the afternoon as a trailing shortwave quickly traverses the region.

As this low brings in a colder air mass, temperatures are expected to drop near or below freezing tonight across many valleys, threatening early season agriculture. This includes Eastern Juab/Millard counties, Sanpete and Sevier valleys, and Southwest Utah, expanding to eastern valleys tomorrow night before a brief warming trend on Wednesday.

Our attention then turns to the next, stronger storm system that looks pretty winter-like. Although temperatures rebound on Wednesday under shortwave ridging, a longwave trough will quickly move through the PacNW southward into Utah by Thursday. The baroclinic zone associated with this trough initially looks very impressive with a strong pressure gradient and plummeting snow levels down to valley floors behind the front. This system will also usher in more moisture with the heaviest precipitation expected along and behind the front. Current timing, which actually has pretty decent agreement among model guidance, suggests the cold front moves across the state between Thursday morning and late Thursday night. A minority (~25%) of ensemble members even suggest an earlier progression of the front.

After the frontal passage, orographic showers will likely hang on overnight into Friday morning, particularly for areas favored in westerly to northwesterly flow. This timeframe will also bring the best chances for valley snow, particularly after sunset. Lake-effect will also be something to watch, given low-level moisture, steep lapse rates, cold temperatures, and a climatologically warm Great Salt Lake. Still a bit early to tell, but this could locally enhance snowfall totals in the Salt Lake Valley and/or northern Wasatch Front. Speaking of snow totals...current 25th-75th percentile output suggests 6-12 inches in the northern mountains with locally higher amounts in the Upper Cottonwoods. Across northern valleys, amounts will likely remain fairly minor given warm antecedent conditions, around 1-3 inches (2-5 for the Wasatch Back).

Freezing temperatures will return for most areas by Friday and Saturday mornings...across all but lower elevations in extreme southern Utah (St. George, Lake Powell, Zion).

Late Friday into the weekend, quieter conditions are expected as high pressure rebuilds. However, this may not last long, with model guidance suggesting another storm system early to mid next week.

REST OF UTAH AND SOUTHWEST WYOMING

Northern Utah and southwest Wyoming are expected to see VFR conditions under mid and high clouds. Across central and southern Utah, periods of valley rain and mountain snow will result in areas of mountain obscuration as well as MVFR to IFR conditions through Tuesday morning. Snow levels are expected to fall as low as 6kft overnight, and as such, southern/central Utah terminals near or above that elevation will have the greatest potential for IFR (or even briefly LIFR) conditions.

SLC WATCHES/WARNINGS/ADVISORIES

UT...Freeze Warning until 9 AM MDT Tuesday for UTZ103-116-118-119-122.

Freeze Watch from Tuesday evening through Wednesday morning for UTZ114-115-120-121-130.

Freeze Warning from 9 PM Tuesday to 9 AM MDT Wednesday for UTZ116-118-119-122.

Winter Weather Advisory until 3 PM MDT Tuesday for UTZ117-125.

WY...None.