textproduct: Salt Lake City

KEY MESSAGES

- Freezes are expected again Friday night in the Sanpete Valley and eastern Box Elder County.

- An active pattern will bring the threat of 6+ inches of snow to the higher terrain of Utah Saturday night into early Tuesday morning.

- Widespread valley rain is expected with the heaviest amounts north of I-70 through Monday evening.

- Additional freezes may impact the Sanpete and Sevier Valleys and southwest Utah Monday night.

DISCUSSION

A gradual warming trend continues across the CWA today and will continue into Saturday. Saturday will also be the start of an active period of weather that will last through at least early Tuesday morning across the region

With both the polar and sub-tropical jet active across the western United States, a complex and chaotic weather pattern will ensue. A persistent, quasi-stationary upper level low centered over Saskatchewan will remain in place through at least Monday. A shortwave trough rotating around the west side of that upper level low will shift into the northern Intermountain Region Saturday. Meanwhile a shortwave trough embedded in the sub-tropical jet will shift into the Desert Southwest Saturday afternoon into early Sunday.

These two systems will phase to an extent over Utah Sunday...with significant forcing for a band of moderate to heavy precipitation setting up over Utah. While yesterday's ensemble members depicted this band's location from the Idaho border south to the Arizona border depending on the member, today's guidance has become more consistent in placement. The majority of ensemble solutions suggest this band will set up along and northwest of a line from roughly Kings Canyon north and east to Evanston, WY. This would put most of northern and portions of central Utah in a bullseye of moderate to heavy valley rain and periods of moderate to occasionally heavy mountain snow. The 25th to 75th percentile for precipitation through Monday night across the valleys north of I-70 is around 0.50-1.00 inches, though the Wasatch Front and north is closer to 0.60-1.25 inches given the location of the heavier precipitation band in many ensemble members. The largest 25th to 75th percentile spread is across the upper Cottonwoods, where the 25th to 75th snow water equivalent is 1.5 to 2.75 inches through Monday night.

Expect the northern stream trough to shift through the region Monday afternoon into Tuesday morning, bringing additional precipitation to the region, with a 25% chance the Wasatch Front could exceed another 0.50" and the upper Cottonwoods 1.00" of snow water equivalent. Again this is the area of most diverse spread due to orographics and potential lake enhancement.

For now, the only headlines are related to two valleys that will see freeze conditions tonight. Snow totals for winter weather advisories for the mountains are marginal, with less than a 50% chance of seeing 9"+ for the Wasatch, 6"+ for the remainder of the mountains in 24-36 hours. Something future shifts will need to continue to monitor. That said, anyone with plans the later half of the weekend into early next week across the higher terrain of Utah should be prepared for winter conditions, cold temperatures, and accumulating snow.

REST OF UTAH AND SOUTHWEST WYOMING

VFR conditions will persist for the entire airspace through the period. Dry and stable conditions will continue with a few high clouds. Winds will be diurnal and relatively light.

SLC WATCHES/WARNINGS/ADVISORIES

UT...Freeze Warning from 10 PM this evening to 9 AM MDT Saturday for UTZ103-118.

WY...None.