textproduct: Salt Lake City

KEY MESSAGES

- Showers will continue over central and southern Utah through the overnight hours, with the focus of showers and thunderstorms shifting to northern Utah and southwest Wyoming Monday afternoon and evening. Any storms that develop will be capable of producing gusty outflow winds.

- Showers will be possible across just about all of Utah and southwest Wyoming Tuesday as a trough passes by, with the focus shifting to eastern Utah Tuesday evening. Some showers will continue into Wednesday morning before tapering off.

- Temperatures dip to near seasonal normals Tuesday into Wednesday, but building high pressure beginning late Wednesday will allow temperatures to allow mild temperatures to return by the weekend.

DISCUSSION

A broad Pacific low is slowly rotating into the Great Basin this evening. Utah and southwest Wyoming remains under a south to southwest flow out ahead of this feature, and that flow is drawing moisture northward into the forecast area. The combination of increasing moisture and instability from the front side of the low has allowed scattered showers with a few thunderstorms to develop over southern Utah.

Storms earlier were more discrete, with very dry low levels, and this brought some gusty outflow winds, with areas like St. George, Cedar City, and Kanab seeing periods of gusts in excess of 40 mph. Moisture is starting to spread into the lower levels and overall the showers have coalesced. This has decreased the threat of gusty winds somewhat, but there is still at least a low chance of gusts in excess of 40 mph with any storms that develop.

With shortwave energy from the elongating low lifting northward overnight, the focus of showers will shift to central Utah Monday morning and into northern Utah and southwest Wyoming during the afternoon and early evening. Overall, guidance is trending toward showing less moisture and instability over northern portions of the area than at this time yesterday, so the anticipated coverage of showers and thunderstorms has decreased overall. Still, the threat of gusty winds remains with the thunderstorms given inverted-v profiles.

The low is expected to cross into the Desert Southwest during the day Tuesday. Most guidance yesterday showed it moving across Arizona and into New Mexico by early Wednesday. However, latest guidance is pulling the trough expected to drop south into the central United States farther west at that time, blocking the Pacific low and likely causing it to diminish or at least weaken, and potentially bringing a backdoor front into southwest Wyoming and northeast Utah. This change brings the focus of convective potential Tuesday to those areas in the vicinity of the backdoor front, though at least isolated showers remain possible across at least most of the remainder of the area. This track of the central United States trough would also shift the focus of precipitation to eastern Utah for Tuesday night, and allow for at least a low chance of showers into Wednesday morning before the system tracks away from the area.

As the trough moves away, there is high confidence that a broad Pacific ridge will build across the West late Wednesday into Thursday. Beyond that, the vast majority of guidance still shows the ridge continuing to strengthen over the weekend, bringing very mild temperatures. However, some outlier guidance (including the deterministic GFS), show a Pacific Northwest trough moving over the top of the ridge and pushing it back west, allowing a trough to move across the forecast area over the upcoming weekend. Considering how this winter and spring have been, am skeptical about the trough potential but will continue to monitor.

REST OF UTAH AND SOUTHWEST WYOMING

A broad area of high- based showers and gusty outflow winds across the southern half of UT will continue to shift northward overnight, largely weakening before reaching the Wasatch Front. However, outflow from these showers could produce a period of gusty S winds across central/northern UT after ~06-07z. The lightning threat has largely ended, though scattered showers and isolated thunderstorms capable of producing gusty and erratic outflow winds are expected to redevelop after 19z across primarily N-UT/SW-WY. VFR conditions will prevail outside of any VIS reductions from BLDU.

SLC WATCHES/WARNINGS/ADVISORIES

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