textproduct: Salt Lake City

KEY MESSAGES

- A landfalling atmospheric river will bring a long duration period of valley rain and mountain snow from Wednesday on into the upcoming weekend.

- Strong, gusty winds are expected Wednesday particularly across Uinta County, WY and high northern terrain. A High Wind Watch has been issued for Uinta County, WY Wednesday for potential gusts in excess of 60 mph.

LONG TERM (After 12Z/5AM Friday)

Another atmospheric river event will track into the PacNW Thursday. Through much of Friday, southwest Wyoming and Utah will be between the exiting and incoming storm systems. Upslope orographics and weak forcing will allow for northern mountain snow showers above 7000 feet much of Friday. Also between systems, similar to Wednesday ahead of that atmospheric river, winds will be enhanced. South the southwest winds will be maximized on northern mountain ridgelines and throughout southwest Wyoming.

There is good agreement with models and ensembles that the jet associated with abundant moisture advection will slide southward through Friday, with increasing moisture advection and better forcing pushing into southwest Wyoming and northern Utah Friday into Saturday. Snow levels will start around 7000 feet near the Idaho border and 8000 feet for the Cottonwoods. Snow levels will increase and decrease some, but stay consistent through the event, as the main forcing will be the zonal jet. This will transport abundant moisture, bringing moderate to heavy mountain snow. Snow ratios will be low through the event, ranging from 5-10:1 for the northern mountains, with the greatest ratios for the Bear River Range. Water content will generally range from 0.5-1.0" for the western Uinta Mountains and Cottonwoods, with 0.75-1.5" for the Bear River Range. There will be a big range of snowfall totals, with totals likely exceeding 1 foot for ridgelines near the Idaho border. There will be a decreasing trend from north to south.

Moisture advection will diminish later Saturday as the forcing and moisture lift out of the region, but valley rain and mountain snow showers will continue for southwest Wyoming and northern Utah. Temperatures from Friday into next week will be warmer than normal, with valley highs in the 50s for most locations.

For the end of the weekend into next week, there is good agreement on another atmospheric river event into the western U.S. Models generally have the track of this storm system more southward from the previous. There would be enhanced southwest flow ahead of it, with the better moisture surge north and west of Utah. The track would lead to more downslope orographics to the west from the Sierra Nevada Mountains, so a significant mountain snow event is not anticipated through the start of the week.

AVIATION...KSLC

There is a 10-20% chance for fog that would build in from the north from 12-15Z that would be capable of MVFR or lower conditions. Scattered clouds in VFR range will transition to broken clouds around 20Z. Light southeast winds will last through 20Z when winds transition to light northwest.

REST OF UTAH AND SOUTHWEST WYOMING...Valley inversion conditions will allow fog or low clouds in MVFR range or lower, particularly for KLGU. Clouds will build from the northwest through the day, with scattered clouds transitioning to broken throughout southwest Wyoming and northern Utah from 15-21Z. Winds will be relatively light throughout Utah, with southwest gusts around 20 knots for southwest Wyoming.

SLC WATCHES/WARNINGS/ADVISORIES

UT...None. WY...High Wind Watch from late tonight through Wednesday evening for WYZ021.