textproduct: Salt Lake City

KEY MESSAGES

- Freezes are expected again tonight 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 closed low remains in place over southern Saskatchewan while weak shortwave disturbances continue to rotate around it. One such disturbance is currently rippling through southeast ID into western WY. This has resulted in a shallow cold front which has made its way through the northern half of Utah. This front will weaken and push just a bit farther south through the night. With skies trending clear across northern Utah, expect excellent radiative cooling to bring freezing temperatures to eastern Box Elder County tonight. A freeze is also expected in the Sanpete Valley, with more patchy freezing conditions in southwest Utah, even though some cloud cover will persist late into the night.

On Saturday, another, stronger, shortwave trough will rotate around the aforementioned low and carve into the PacNW. Meanwhile, another storm system will approach CA from the Pacific. This will allow for increasing southwesterly flow over Utah. Some moisture will start to spread into the area and bring some isolated showers to the spine of Utah for the afternoon. Thereafter, a more anomalous plume of moisture will spread into the area Saturday night as the Pacific trough approaches. Widespread precipitation will be likely across the area Saturday night through Sunday, with the greatest amounts expected over the Wasatch Front and Wasatch Mountains. Snow levels will be high, generally around 7-8 kft.

As this trough exits the area, the trough over the PacNW will follow quickly on its heels, bringing another round of widespread precipitation to the area on Monday. Not much of a break in precipitation is expected between the two storms. Snow levels will be a bit lower with this second storm, in the 6.5-7.5 kft range.

The two storms combined will bring significant precipitation to portions of northern Utah. There is a 40-70% chance of greater than 1 inch of water across the northern and central Wasatch Front and 40- 75% chance of greater than 2 inches in the Wasatch Mountains. Most other valleys have a 40-70% chance of 0.5 inches while other mountains have a 40-70% chance of 1 inch. Given that snow levels and snow densities remain somewhat high, snow amounts will be moderated a bit, with generally 6-12 inches on the higher ridgelines with locally higher amounts in the upper Cottonwoods.

Models indicate another shortwave disturbance grazing the area which should bring additional, generally light, precipitation to mainly northern Utah for Tuesday. Thereafter, uncertainty increases with the evolution of the next upstream storm system. While there is potential for active weather to continue into late week, the details have yet to really come together at this time.

REST OF UTAH AND SOUTHWEST WYOMING

VFR conditions will persist for the entire airspace through the period. Dry and stable conditions will continue with patchy mid and high clouds tonight. These clouds will increase again by Saturday afternoon. Winds will be diurnal and relatively light for most terminals, except northern Utah and southwest Wyoming terminals which will remain northerly and occasionally gusty through late tonight.

SLC WATCHES/WARNINGS/ADVISORIES

UT...Freeze Warning until 9 AM MDT Saturday for UTZ103-118.

WY...None.