textproduct: Salt Lake City

KEY MESSAGES

- Showery precipitation with snow levels above 9000 feet moves into northern Utah this afternoon, continuing through Sunday.

- A more organized upper level low will cross the region Monday, bringing more widespread precipitation to the state and slightly higher precipitation intensity for northern Utah.

- A colder but less moisture rich system will move through the Great basin later Wednesday into Thursday, with potential for limited lower elevation snow amounts.

DISCUSSION

Modest moisture advection into the region courtesy of mostly zonal westerly flow overhead will result in some scattered showers developing this afternoon across northern Utah. This shower activity is expected to continue into Sunday, before increasing southwesterly flow aloft shunts any lingering moisture northward. Given warm temperatures aloft (H7 temps peaking around 1-2C), snow levels will be very high through this period, remaining steady around 9000-9500 feet through late Sunday. As such, impacts will be minimal as snow accumulation will remain confined to the highest terrain of northern Utah.

A more substantial storm is shaping up to impact the region late Sunday through early Tuesday, bringing more widespread and substantial measurable precipitation mainly to northern and central Utah. An upper-level closed low currently off the coast of northern California moves inland late Sunday, yielding increasing moist, southwesterly flow aloft across the region. An associated jet max moving overhead through Monday will bring a shield of precipitation through the region, with best dynamics and thus heaviest precipitation favored across northern Utah. The ECMWF Extreme Forecast Index remains unchanged overall from previous forecast, with west-central to far northeast Utah still favored for anomalous precipitation from this setup on Monday. Modest cold air advection from this upper-level low will result in gradually lowering snow levels through this event, with snow levels around 9000-9500 feet at the onset of precipitation late Sunday dropping to around 6500-7000 feet by late Monday. Given these high snow levels, impacts will again be overall limited, though travel disruptions are possible for mountain routes (mainly >8000 ft) during the latter half of the storm. Post- frontal northwesterly flow developing late Monday into early Tuesday may allow for lingering showers across the Wasatch, with orographic enhancement possible across the Upper Cottonwoods.

There remains good agreement in a shortwave trough dropping into the Great Basin from the Pacific Northwest late Wednesday into Thursday, which would yield a slightly cooler storm system. Forecast guidance has trended warmer across northern Utah with recent runs, which has all but eliminated valley snow chances across the area -- chances for accumulating snowfall have dropped to less than 10% for the Wasatch Front, though a 20-30% chance still exists for the Sanpete and Upper Sevier Valleys and the I-15 corridor across central Utah. Looking like another modest snowfall for the mountains, with a 30% chance for northern mountains and the Tushars to see 6 inches or more of snow, except a 60% chance for the Upper Cottonwoods.

REST OF UTAH AND SOUTHWEST WYOMING

Moisture associated with an approaching Pacific system will increase through the TAF period. At southern terminals, this will result in an increase to mid/upper level cloud cover. At northern terminals, a more noted increase to cloud cover ~7-25 kft is expected. Precipitation chances (~20-40%) will also increase at northern terminals Saturday night through Sunday, and will bring periods of further degraded CIGS/VIS as well as some variability to winds. Otherwise, winds areawide are generally anticipated to follow a diurnally normal pattern.

SLC WATCHES/WARNINGS/ADVISORIES

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