A forecast for a series of thunderstorms and possibly heavy rain showers had two-thirds of Utah under a Flash Flood Watch through Wednesday night.

The advisory, which kicked in at 10 a.m., included southern, central and northeastern Utah. The National Weather Service warned of the potential for flooding in slot canyons, on mountain slopes recently denuded by wildfires and along normally dry washes and creek beds in steep terrain.

The risk for mudslides and rock falls along stretches of vulnerable roadways also was elevated as the monsoonal moisture out of the southwest rolled into the region.

All that storm activity did little to affect the state's continuing trend of above-normal daytime high temperatures — except to make conditions more humid. What rain came also failed to alleviate tinder-dry and windy conditions in northwestern Utah that prompted a "Red Flag" warning through 10 p.m. Wednesday.

Thunderclaps were expected over the Salt Lake Desert all the way to the Nevada and Idaho borders, but the lightning was expected to arrive dry. Buffeted by winds of 30-45 mph, the parched range and grass lands were ready to ignite.

High temperatures along the Wasatch Front will be in the low-90s on a stormy Thursday, down a few degrees from Wednesday; Friday's forecast calls for highs in the mid-90s as the storms move out of the region.

The same temperature ranges were expected for southern Utah, where stronger storm activity was predicted to bring rain through the remainder of the work week to cool thermometers from their recent triple-digit readings.

The Utah Division of Air Quality, noting the coming storm activity, predicted modest improvement ahead. The state's usual air quality trouble areas — Salt Lake, Davis, Utah, Tooele, Weber and Box Elder counties — will improve from the "orange," or unhealthy category to "yellow," or moderately polluted conditions by Thursday.

The rest of the state was generally "yellow" Wednesday, though Washington, Carbon, Duchesne and Uintah counties will be "green," or healthy on Thursday.

The Intermountain Allergy & Asthma website put mold at "high" on its pollen index as of Wednesday, but other allergens rated "low," or did not register.

For more extensive forecast information visit the Tribune's weather page at http://www.sltrib.com/news/weather/.

remims@sltrib.com

Twitter: @remims