textproduct: Salt Lake City

KEY MESSAGES

- Mild temperatures with highs around 10 to 15 degrees above normal will persist through Friday, along with some isolated afternoon showers.

- A broad system approaches the area Friday into Saturday, resulting in increasingly gusty conditions Saturday. There is a 40-50% chance of wind gusts in excess of 45 mph across portions of Utah's West Desert Saturday and Sunday afternoon.

- Unsettled conditions return Saturday, initially bringing periods of rain and thundershowers as well as high elevation snow. A colder system will then reinforce widespread precipitation chances, lower snow levels, and bring a period of more substantial mountain snow alongside continued breezy winds.

DISCUSSION

A very weak area of convergence near a remnant frontal boundary has been resulting in some isolated high-based showers across northern Utah this morning. These haven't had much in the way of water associated with them, rather just some light sprinkles. Similarly, there is a band of thicker cloud cover near this remnant frontal zone, with mostly just some higher clouds elsewhere around the region. Anticipate clearing will allow some destabilization this afternoon, and in turn will see a few more showers and a thunderstorm or two develop near this remnant boundary. Elsewhere precip chances will be more muted, with generally just some cumulus developing off of the terrain. Temperatures will once again be around 10 to 15 degrees above seasonal normal for afternoon highs.

On Friday a broad Pacific system will start pushing inland along the California coast. Locally this will result in a gradual enhancement to deeper southwesterly flow, as well as some modest moisture advection and midlevel height falls. Models also suggest some subtle shortwave energy advecting through overhead coincident with daytime heating, and as such expect some isolated shower development across the area, especially along and adjacent to the higher terrain. Temperatures will remain well above normal.

The Pacific trough will continue to gradually move inland, shift into more of an open wave, and lift through the Great basin Saturday. The combination of moisture and enhanced synoptic forcing will result in more widespread precipitation chances across the area. Areas of showers will likely be ongoing through the morning hours, with coverage increasing in the afternoon as daytime heating results in modest destabilization. With the wave moving through overhead, shear will also be slightly enhanced, which with the instability should support some thunderstorm activity as well. The fast storm motion should help to preclude widespread flooding concerns, but all the same if a stronger cell works over a rain sensitive area (burn scar, slot canyon, dry wash), it could still pose a threat. Given the introduction of a bit of shear, also cannot rule out a couple more organized storms/segments (as CAMs such as the RRFS suggest). The ECM EFI does highlight much of the area as having anomalous CAPE/shear, also highlighting this potential. Still, would put this as low confidence at this time.

In addition to the precipitation/storm potential on Saturday, the enhancement to deep southwesterly flow will result in enhanced southwesterly winds and gusts areawide. The strongest signal remains over portions of the West Desert region where there remains around a 40-50% chance of wind gusts at or in excess of 45 mph. While more modest gusts are anticipated elsewhere, would expect other typical hotspots such as the Tooele Valley or areas near the northern portions of terrain features where winds downslope to have some strong gusts as well (e.g. Oquirrh/Stansbury Mountains).

After a brief lull late Saturday into the overnight, a secondary deep trough starts to dig into the Great Basin. Models have slowed down on an associated cold frontal passage a bit until later in the afternoon to evening, and as such expect strong south to southwesterly wind gusts to persist in some capacity prior to frontal passage. Precipitation chances will once again increase through the day ahead of the front, becoming maximized along and behind the front as the core of the trough slowly moves in. Shower chances then remain elevated through Monday night to Tuesday as cyclonic flow on the back end of the trough maintains forcing. These shower chances will be maximized in the higher terrain, especially where northwest flow is a favorable orographic element.

As alluded to with the cold front, this system will have a more potent tap of cold air associated with it. Prefrontal precipitation will be milder with snow levels around 7500 to 8000 feet, but gradually fall closer to 6000 to 6500 feet following frontal passage. With good moisture transport, models continue to support around a 30-40% chance of water amounts at or in excess of 1" for much of Utah's mountains, and good odds of some sort of measurable precipitation more or less areawide. With the aforementioned snow levels, this will result in fairly appreciable mountain snowfall accumulations. Probabilities have also not shifted much with around a 30-50% chance of 6" or more of snow for much of Utah's mountains, with locally higher amounts in favored spots. Given prolonged northwesterly flow on the back end of the system, there's still around a 30-50% chance of 12" or more snow in places like the Upper Cottonwoods. Will still have to watch trends as forecast to forecast the timing and overall water amounts have and will likely continue to shift some. Temperatures will also drop markedly behind the front, with daytime highs more in the 5-10 degrees below normal range.

REST OF UTAH AND SOUTHWEST WYOMING

VFR conditions are expected for all regional terminals today. Expect generally terrain driven breezes for most terminals except those across southern Utah, where enhanced southwesterly winds will continue through this evening. Otherwise, light winds are expected overnight, with gusty south to southwesterly winds developing across the airspace late Friday morning.

SLC WATCHES/WARNINGS/ADVISORIES

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