textproduct: Salt Lake City

KEY MESSAGES

- Freezes will impact many Utah valleys tonight. Freezes are not expected to impact the Wasatch Front or lower Washington County.

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

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

DISCUSSION

As subsidence builds into the region this afternoon, showers will continue to become more isolated. With mostly clear skies tonight, many Utah valleys (outside the Wasatch Front and lower Washington County) will see freezes once again. Freeze Warnings remain in effect and no changes are expected, though outlying areas near Spanish Fork, Payson, and Santaquin in southern Utah County may approach freezing tonight.

While most of Utah will see a gradual warming trend through Saturday, a nearly stationary upper level low will remain across Saskatchewan through at least Monday. By late Saturday, a shortwave trough rotating around this upper level low will be shifting into the northern Intermountain Region. Meanwhile, an upper level low embedded in the southern stream will approach the southern California coast Saturday. This atmospheric chaos will introduce a lot of potential variance to the forecast from Sunday through at least late Monday.

The previously mentioned southern stream upper level low will shift into the Desert Southwest late Saturday night into Sunday while the shortwave trough rotating around the base of the upper level low shifts into Idaho. This will likely create an area of enhanced lift and precipitation somewhere between the Idaho and Arizona borders across Utah. This is one of the main cruxes of the forecast...where this band of enhanced precipitation will set up Sunday morning into Sunday evening.

As the northern stream shortwave trough rotates through Nevada Monday, additional precipitation is likely across much of the region. Given this is a northern stream trough, snow levels will trend lower...toward 7000 feet...with this portion of the event.

All told, the 25th to 75th percentile for snow amounts for the first part of the storm for the northern mountains ranges are 5 to 10 inches, with locally up to 18 inches for the upper Cottonwoods through 6 AM Monday, followed by another 1 to 4 inches, locally up to 8 inches in the upper Cottonwoods from Monday 6 AM to Tuesday 6 AM. For the central and southern mountains, largely north of UT-20, expect 4 to 8 inches after midnight Saturday night through 6 AM Monday, with another 1 to 4 inches through 6 AM Tuesday. Given the probability of warning amounts is less than 50% and confidence in the placement of the location of best forcing for precipitation is low, no winter headlines are needed at this time.

For those in the valleys, a general 0.25 to 0.50 inches of rain is expected from later Saturday through Monday evening south of I-70, with the valleys north of I-70 seeing 0.50 to 1.00 inches of rain north of I-70 for the same time period.

Additional freezes are likely (70%+ chance) for the Sanpete and Sevier Valleys and normally colder valleys of southwestern Utah Monday morning and Tuesday morning with this colder airmass in place.

REST OF UTAH AND SOUTHWEST WYOMING

Low level cloud cover and isolated rain showers continue across the northern area this morning and into the early afternoon before conditions improve. Areas of MVFR conditions can be expected through around 19-20Z before the environment dries and clouds begin to clear. For the southern area, anticipate largely clear skies with increasing high level clouds early tomorrow morning. Winds will remain out of the west to northwest across the northern area but will return to terrain driven overnight while the southern area will maintain light terrain driven flows through the remainder of the day and overnight hours.

SLC WATCHES/WARNINGS/ADVISORIES

UT...Freeze Warning from 10 PM this evening to 9 AM MDT Friday for UTZ103-114>116-118>120-122.

WY...None.