textproduct: Salt Lake City

KEY MESSAGES

- A Pacific Northwest storm system will bring a cold front through Utah and southwest Wyoming on Thursday, resulting in significant snow for Utah's mountains and many mountain valleys, with light snow also likely for most valley locations. Some snow will linger into Friday as the main trough makes its way through the area, with a chance of lake effect showers for portions of the Wasatch Front.

- Dry and increasingly mild conditions will return for the upcoming weekend, with a return to unsettled weather possible by the middle of next week.

DISCUSSION

The Pacific low has exited Utah and southwest Wyoming this evening, allowing high pressure to move back in. Remaining clouds are actively dissipating per satellite imagery, with clear and tranquil conditions anticipated overnight. Temperatures will quickly rebound tomorrow in a dry southerly flow, with maxes averaging 10F above seasonal normals.

A Pacific Northwest storm system will move onshore during the day Wednesday, with its center reaching central Nevada by midnight Thursday. A cold front on the leading edge of this system will move into northwest Utah around that time, sliding southeast across the area through the day Thursday. A band of precipitation, snow for the mountains and mountain valleys and a mix of rain and snow for the valleys, will develop along and behind the front, with some relatively heavy rates anticipated. In cold pool instability, showers will continue Thursday evening into Friday, with a secondary maximum of precip rates early Friday with a second weaker system on the heels of the first.

Overall, snow amounts have gone down just a bit compared to the morning forecast, showing some uncertainty remains about the amount of moisture in the airmass accompanying the system, as well as the speed of the front, how long precipitation lingers on Friday, and the potential for lake effect Friday morning for the Wasatch Front. Despite the uncertainty in those areas, confidence remains relatively high in significant snow for southwest Wyoming, the mountains of Utah, and some adjacent mountain valleys, with going Winter Weather Advisories and Winter Storm Watches covering this threat well. Overall, guidance indicates valley accumulations are likely for the Cache Valley and less likely for the remainder of the Wasatch Front and some southern Utah valleys. Any accumulations that occur will be on the light side outside of any lake bands, should they develop.

The majority of guidance indicates the secondary system will close off and move into the Desert Southwest by late Friday as the primary system exits to the east, bringing dry conditions with mild temperatures returning by Sunday. Beyond that, the forecast gets a bit more murky, with the guidance having its usual trouble coming to agreement on the evolution of the closed low over the Desert Southwest, though more guidance is now showing the system moving east early next week, away from the area. Guidance also shows another Pacific Northwest storm system moving onshore early this week, but there is quite a bit of spread with how far south it gets, indicating great uncertainty with regard to the potential impacts for Utah and southwest Wyoming.

REST OF UTAH AND SOUTHWEST WYOMING

Benign weather with VFR conditions and generally diurnally normal winds to persist through much of the TAF period, with the exception of a low chance (~15-30%) of VIS reductions at terminals such as LGU/EVW early Wednesday morning. A cold front will begin to sweep through northern terminals late Wednesday evening into the overnight, bringing a period of stronger W to NW winds, precipitation, and lowered CIGS/VIS accordingly (especially where snow can mix in or dominate).

SLC WATCHES/WARNINGS/ADVISORIES

UT...Winter Weather Advisory from 2 AM Thursday to 5 PM MST Friday for UTZ108.

Winter Storm Watch from late Wednesday night through Friday afternoon for UTZ110>112.

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

Winter Storm Watch from late Wednesday night through Friday afternoon for UTZ117.

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