textproduct: Salt Lake City

KEY MESSAGES

- Building high pressure will bring a steady warming trend in temperatures through Thursday as conditions dry.

- Monsoon moisture will move back into Utah and southwest Wyoming late in the week, persisting through at least early next week. This will bring an increased threat of showers and thunderstorms capable of producing flash flooding.

DISCUSSION

High pressure centered over western AZ tonight through Wednesday will maintain an dry west-northwest flow over UT. Latest analysis shows around 0.8-0.9 inches of PWAT across the area. This should be enough to result in isolated to widely scattered diurnal and mostly terrain-based showers and thunderstorms.

The high pressure will gradually shift east towards CO/NM by Friday, and a bit farther east for the weekend. This will bring a gradual return of monsoonal moisture to the area, with showers and thunderstorms increasing over the mountains and southern Utah Thursday before becoming more widespread over the forecast area Friday through at least the early part of next week. With the increased coverage of thunderstorms and arrival of deeper moisture coupled with added dynamics from a series of weak disturbances crossing the area, the threat of flash flooding will increase during this timeframe. A Marginal Risk of Excessive Rainfall begins as soon as Thursday across portions southern Utah and will be more widespread across the area by Saturday.

With the arrival of the deeper moisture, temperatures will trend downward towards the end of the week into next week. Until then, however, temperatures will remain on the warm side, with highs around 5-10 degrees above normal. The NBM currently has a 25-30% chance of SLC reaching 100F Thursday-Friday. However, with the warm bias commonly exhibited locally by the NBM in the warm season, suspect that the chance of reaching 100F is much higher, especially on Thursday, so have adjusted temperatures to reflect this thinking. HeatRisk also falls into the Red (Major) category in many valley areas on Thursday, but the increased threat of heat related illness will be mitigated due to overall acclimation during the season.

AVIATION...KSLC

There is low confidence in wind direction overnight; although southeasterly is likely to be the dominant direction, there is a chance to go back to northerly around 4-7kts between 06-11z. Otherwise, expect VFR conditions with FEW-SCT mid-level clouds.

REST OF UTAH AND SOUTHWEST WYOMING...Winds will remain fairly light and terrain-driven overnight, with VFR conditions prevailing. Isolated thunderstorms will redevelop Wednesday afternoon across primarily eastern Utah with chances for gusty outflow winds.

FIRE WEATHER, Issued 414 PM MDT Tue Aug 18 2026

High pressure to the west of Utah will bringing a warming and drying trend through Thursday, bringing temperatures up to 10F above seasonal normals by Thursday afternoon. Relative humidities will drop, with pockets of critically low RH values developing by Thursday. Winds could be enough to bring isolated pockets of critical fire weather conditions Thursday afternoon, but coverage is looking increasingly limited. As the ridge moves eastward Friday, monsoon moisture will move into the area from the south, remaining in place through early next week. This will bring increased potential for wetting rainfall, improved RH values, but also the potential of storms that could produce heavy rain that could lead to flash flooding.

SLC WATCHES/WARNINGS/ADVISORIES

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