textproduct: Salt Lake City

KEY MESSAGES

- Building high pressure keeps conditions dry and mild through the remainder of the week.

- Mountain snowfall appears increasingly likely across most of the forecast area, starting with northern UT, beginning as early as Monday evening. Most valleys can expect rainfall from this system.

- A shift to a cooler and unstable pattern will follow for the remainder of next week.

DISCUSSION

Upper level ridging is forecast to persist across much of the western U.S. through Friday ahead of an upper low just off the southwestern CA coastline. This low is forecast to phase into the mean flow as a shortwave trough and swing north, grazing western UT. While it is expected to weaken, two things will occur with this trough ejection; some light showers, albeit gusty, may form across southwest UT tomorrow afternoon. Additionally, this trough will serve to help break down the persistent western ridge and continue pushing it southeast.

As we enter the weekend, a closed low will develop well to our south with height rises just to our north. This will assist in reinforcing warmer, drier conditions for this weekend across much of the state. Some weak ascent within a diffluent flow regime ahead of this closed low may result in some higher elevation mixed precipitation showers across higher elevations within southern UT, though this will likely not result in much rainfall/snowfall accumulation. Transient ridging aloft builds in quickly behind this system across the Great Basin ahead of an incoming longwave trough over the Pacific.

Come Sunday evening into Monday morning, a broad longwave trough is forecast to push into the Pacific NW with broad diffluence beginning to overspread much of UT by Monday evening. Chances for precipitation Monday evening will cap around 30-40% across high terrain across northern UT with low chances (10-20%) for valley rainfall along the majority of the Wasatch Front and Tooele Valley. Come Tuesday afternoon, confidence remains high regarding a fast moving convective band approaching the area along an associated cold front which will raise PoPs notably for the time. However, speed, timing, and moisture quality still remain somewhat uncertain which will greatly impact snow and rainfall accumulations. Additionally, the system continues to trend warmer which has all but killed any hope for accumulating valley snowfall with this upcoming system.

Looking even further, the pattern does appear to remain active following this system. This is due to the persistent blocking ridge having (thankfully) moved off to our southeast due to the earlier systems. Following Monday/Tuesdays system, the upper level pattern appears to remain quite active with multiple systems potentially impacting the west in some capacity. While moisture abundance appears more favorable with these systems, there remains uncertainty with southern extent and overall amplification of the troughs. Currently, ensemble clusters are split nearly 50/50 regarding how far south these systems will occur. For an event favoring precipitation across our area, we will want higher geopotential heights aloft south of the incoming trough axis to keep it further north (indicated in 50% of ensemble guidance). Even if the system swings further south, at least some precipitation would be expected, though southern UT would be favored significantly over northern UT in that regime. Details should be ironed out over the coming days, and this forecaster still remains hopeful that some snow could return to UT next week.

REST OF UTAH AND SOUTHWEST WYOMING

No significant weather expected as high pressure maintains mostly clear VFR skies and stable conditions. Generally expect light diurnally normal winds at area terminals into Friday. There is a low (less than 10% chance) of an isolated shower or two across SW UT terminals Friday afternoon, with corresponding potential for modestly gusty erratic outflow winds (~25-35 kts).

SLC WATCHES/WARNINGS/ADVISORIES

UT...None. WY...None.