textproduct: Salt Lake City

KEY MESSAGES, Issued 1033 PM MDT Tue Aug 18 2026

- Building high pressure will bring a steady warming trend in temperatures through Thursday/ Friday 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

Hot and dry conditions are expected to remain in place across Utah and southwest Wyoming through the end of this week as high pressure strengthens over the forecast area. With the upper-level ridge axis cresting overhead Thursday through Friday, anticipate some of the hottest temperatures across the forecast area to fall on these days, especially for the central and northern area. Across southern Utah, the heat is already in place and will be more so maintained during this period of increasing heat across the northern area. With high temperatures in the lower lying valley areas across central and northern Utah reaching back into the triple digits alongside low temperatures in the low- to mid-70s, there will be an increased risk of heat related illness on both Thursday and Friday. Slight moderation of heat is expected on Thursday in central Utah as moisture gradually creeps northward, increasing the amount of afternoon cloud cover and potential for rain cooled downdrafts. As such, the increased heat risk in central Utah is really only anticipated through Thursday while northern Utah will maintain an elevated heat risk on both days. Temperatures decrease across the northern area on Friday as moisture spreads farther northward, decreasing the overall heat risk as daytime high temperatures fall back into the low-90s alongside sufficient overnight relief. Relatively cooler, more seasonable temperatures are expected into early next week while the elevated moisture is maintained.

Speaking of the moisture, the presence of mid-level moisture is currently noted across the forecast area as afternoon heating has allowed for isolated development of showers and thunderstorms over the high terrain in central and northern Utah. This mid-level moisture will remain in place across the central and northern area on Thursday, with increasing lower level moisture anticipated across southern Utah as the high pressure center begins to shift over the Four Corners region. While coverage of showers and thunderstorms are not expected to be widespread across southern Utah on Thursday, whatever storms do form will bring potential for heavier rainfall which may lead to flash flooding if they end up in the wrong spot (i.e. slot canyons, dry washes, recent burn scars, etc.). This threat will increase and expand farther northward on Friday as the persistent high pressure center over the Four Corners region helps to advect anomalous moisture into the area.

By Saturday, much of Utah and soutwest Wyoming will see sufficient coverage of above normal atmospheric moisture, expanding the risk of heavy rainfall and flash flooding across the entirety of the forecast area. This threat is expected to remain in place through at least the Monday/ Tuesday timeframe, with potential to extend into the middle of next week and beyond. In short, expect shower and thunderstorm coverage each afternoon from Friday through Tuesday over the high terrain features across Utah, with an increased probability of heavy rainfall.

AVIATION

KSLC...Generally diurnal winds and VFR conditions will persist at the KSLC terminal through the TAF period. The next wind shift can be expected around 04-05z with southerly drainage winds developing.

REST OF UTAH AND SOUTHWEST WYOMING...VFR conditions prevail across all terminals through the TAF period. Diurnal winds are also expected with little to no chance of precipitation this afternoon.

FIRE WEATHER

Strengthening high pressure will continue to bring a trend of warming and drying across Utah, with high temperatures in many lower lying valley areas reaching back into the triple digits. Alongside the heat, further drying is expected across Utah's West Desert on Thursday with humidity falling by another 5 percent. As such, isolated pockets of single digit humidity are expected in the West Desert on Thursday afternoon. On a positive note, winds will remain generally light and terrain driven through the heat and low relative humidity, keeping significant fire weather concerns low. High-based moisture will make a subtle increase on Thursday, bringing increased coverage of dry thunderstorms over Utah's high terrain. Still, coverage is expected to be isolated to widely scattered.

Moisture continues to increase through the late week and into the weekend, bringing increased coverage of showers and thunderstorms across Utah. With increasing lower level moisture, the potential for wetting rains from individual storms will greatly increase. In addition to the increasing chances for wetting rains, afternoon relative humidity will also significantly improve throughout the mountainous terrain while RH values in the lower elevation valleys of western and eastern Utah will struggle to rise out of the teens.

SLC WATCHES/WARNINGS/ADVISORIES

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