textproduct: Salt Lake City

KEY MESSAGES

- Two storm systems will impact Utah Tuesday through Friday, though uncertainty in snow amounts is still high with each one. The first will be relatively warm, bringing valley rain and mountain snow to much of the area.

- A colder, likely stronger system will bring widespread mountain snow and even a chance for light valley snow by Friday morning, particularly across northern Utah/southwest Wyoming.

- Early season agriculture will likely be impacted by freezing temperatures and frost on Friday and Saturday mornings.

DISCUSSION

Early this afternoon, largely clear skies can be seen on satellite imagery, with just a small shield of cirrus entering southwest Utah in addition to building cumulus over higher terrain in central Utah. Temperatures will again be 15-20 degrees above normal, making for another beautiful early spring day. Conditions will be similar tomorrow, with slightly breezier southwesterly to westerly winds as a low-amplitude trough swings through the Interior Northwest. Low chances for weak showers/virga return during the afternoon given weak instability and lingering mid-level moisture.

However, beyond Monday, our pattern finally changes. The first system will bring gradual cold-air advection and increasing statewide precipitation chances Monday night through early Wednesday morning, with the heaviest precipitation expected Tuesday evening and overnight as the mid-level trough moves through and moisture peaks. Snow levels will still be fairly high, only dropping to 7500-8000ft by Wednesday morning. Interestingly, there is still a large amount of spread in mountain snow amounts for this first system, potentially due to the modeled dynamics of the trough as it moves through. GEFS members generally favor a weaker solution, with 4-8 inches in the Upper Cottonwoods, for example. The EC members, however, suggest more like 12-18 inches through Wednesday morning. A similar magnitude of spread can be seen in the NBM as well.

After a lull on Wednesday, a colder, potentially stronger storm system will bring more precipitation beginning as early as late Wednesday evening. Initially, strong southwesterly winds will promote orographic enhancement for favored areas, with snow levels starting out around 8000ft. These winds are expected to be strongest across western valleys south of I-80, with a 40-50% chance of reaching advisory criteria (45 mph). Still worth monitoring, as a couple deterministic models suggest 700-mb winds approach 50kts by Thursday afternoon. A strong cold front will move through the area from northwest to southeast through the day on Thursday, with a period of moderate-heavy precipitation likely following the frontal passage. As 700-mb temperatures drop to -10C to -12C, snow levels will plummet, potentially dipping below valley floors by Friday morning.

There are still two main areas of uncertainty with this second system. The first is how quickly precipitation tapers off on Friday, which will ultimately influence both valley snow chances and mountain snow amounts. It is still unclear how quickly drier air and subsidence moves in, with an overall trend towards precipitation lingering a bit longer on Friday, even into the evening hours. Currently, valley snow chances are fairly low, particularly given such warm antecedent conditions. The other main area of uncertainty is with the storm track, which will impact mountain snow amounts; similar to the first storm, there is still a large spread in forecast snowfall.

Valley temperatures will be quite chilly by Friday and Saturday mornings, potentially dipping below freezing across all but Lower Washington County and near Lake Powell. However, this isn't expected to last, with model guidance favoring building heights and rebounding temperatures across the western US later next weekend.

REST OF UTAH AND SOUTHWEST WYOMING

VFR conditions will prevail through the TAF period. Gusty winds are expected at KEVW, KCDC, and KSGU this afternoon, improving quickly following sunset. Winds remain elevated tomorrow afternoon out of the W/WSW ahead of an approaching system with increasing upper cloud cover.

SLC WATCHES/WARNINGS/ADVISORIES

UT...None. WY...Red Flag Warning until 9 PM MDT Monday for WYZ277.