textproduct: Salt Lake City

KEY MESSAGES, Issued 928 AM MDT Tue Aug 18 2026

- Building high pressure will bring a steady warming trend in temperatures as conditions dry, bringing a threat of isolated critical fire weather conditions.

- 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, Issued 928 AM MDT Tue Aug 18 2026

High pressure is centered near the Utah/Nevada border this morning with some shortwave energy rippling over the top of it. Thus, seeing clear skies except for southwest Wyoming and areas near the Utah/Idaho border. Satellite derived PWs indicate values primarily in the 0.7 to 1.0 inch range, enough moisture for some afternoon convective development. Coverage should be generally isolated in nature, with the best coverage over northeastern portions of the area, closer to the upper jet associated with the passing shortwave energy.

Under the influence of the ridge, high temperatures today will be similar to yesterday with maxes near seasonal normals. With the ridge expected to amplify and move overhead Wednesday into Thursday, temperatures will steadily warm, with maxes averaging up to 10F above seasonal normals by Thursday, with the greatest departure from normal over northern portions of the area. The airmass will dry out during this time, with relative humidities approaching critical values for portions of western Utah. Locally breezy conditions could bring a few pockets of critical fire weather conditions, but overall the threat is quite isolated. HeatRisk values are forecast to move into the red (major) range for some northern Utah valleys on Thursday, including the west desert and parts of the Wasatch Front. Overall, though, the increased threat of heat related illness will be mitigated due to overall acclimation during the season.

By Friday, there is high confidence that the ridge will move its axis to the monsoon favored position over the Four Corners, drawing deep moisture back northward and increasing the potential of showers and thunderstorms capable of producing flash flooding. This will also remove the threat of critical fire weather conditions and bring temperatures back to near normal for this time of year. The monsoon moisture is expected to remain in place through at least early next week.

AVIATION

KSLC...Northwesterly winds will likely shift to light and southeasterly around 03-04z. However, there is low confidence in wind direction overnight, with potential 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...Showers and isolated thunderstorms across eastern Utah will gradually diminish by 04-05z, with quiet conditions and terrain-driven winds expected overnight. Isolated thunderstorms will redevelop Wednesday afternoon across primarily eastern Utah with chances for gusty outflow winds. VFR conditions will prevail.

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.