textproduct: Salt Lake City

KEY MESSAGES

- A storm system will bring northern mountain snow and strong winds to southwest Wyoming and portions of northern Utah through Wednesday.

- High pressure will be in place Thursday through the weekend, with dry conditions and temperatures around 10-15F warmer than normal. Valley inversions will build as high pressure is in place.

DISCUSSION

Southwest Wyoming and Utah are on the eastern periphery of a ridge of high pressure off the U.S. west coast and on the southern periphery of an atmospheric river (AR) event. This has allowed for enhanced west to northwest winds with isolated to scattered rain and snow showers.

Precipitation has been limited to far northern Utah through Tuesday, as the main moisture plume from the AR is in the PacNW. Being on the southern edge of that and on the eastern edge of high pressure, northwest synoptic winds are advecting some of that moisture into northern Utah. HREF members all indicate the majority of precipitation will be for the Bear River Range near the Idaho border. That is also where the most uncertainty in water and snow content is, with the 25th percentile near 0.5 inch and 75th percentile values at more than 1 inch. There is a sharp gradient, with southern portions of that mountain range with a 25th-75th percentile from a trace-0.15 inch. Further south for the Cottonwoods, there is a similar range of a trace-0.2 inch water content. Snow accumulations for these locations will generally range from a trace-2 inches, with higher totals near the Idaho border. Snow levels will climb from around 8000 feet to 8500 feet Tuesday into Wednesday, with high density snow with low snow ratios.

The set up has also brought gusty west to northwest winds to southwest Wyoming and the northern mountains. Isolated ridgelines have recorded peak wind gusts in excess of 75 mph. For more populated and traveled places, such as the I-80 corridor in southwest Wyoming, wind gusts have exceeded 50 mph, but stayed below High Wind Warning criteria. Winds will be similar Wednesday, but will likely downtrend slightly, with peak wind gusts around 50 mph.

The storm system will exit southwest Wyoming and Utah Thursday with high pressure sliding inland. High pressure will be in place into next week, with dry conditions and much lighter winds for southwest Wyoming and the northern mountains. Temperatures will be warmer than normal throughout southwest Wyoming and Utah through then, but high pressure and lighter winds will allow for valley inversion conditions.

REST OF UTAH AND SOUTHWEST WYOMING

VFR conditions are expected to persist for the entire airspace through the period. Cigs hovering between 4-6kft agl will continue across the northern airspace with some light mountain showers forecast between 01-05Z across the far northern mountains. Elsewhere, conditions will remain dry with light and diurnally driven winds, though gusty SW winds will likely continue at EVW well into the evening hours.

SLC WATCHES/WARNINGS/ADVISORIES

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