Heat warning expires Monday night, but then there could be flash flooding in southern Utah

Even with a chance of rain in the forecast, the air will likely remain smoky along the Wasatch Front.

(National Weather Service) Flash flooding is "probable" at most Utah national parks Tuesday.

An excessive heat warning across much of Utah was set to expire at 9 p.m. Monday, but danger remains in the forecast: possible flash flooding from thunderstorms in southern Utah.

Monsoonal moisture is expected to spread northward from Utah’s southern border, with showers and thunderstorms likely, on Tuesday and Wednesday. Some of those storms could produce heavy rainfall across southern Utah with an increasing threat of flash flooding, the National Weather Service said.

Flash floods are possible in south central and southwest Utah on Tuesday, including areas near Bryce Canyon, Capitol Reef and Zion national parks, the St. George area and Grand Staircase-Escalante National Monument. Slot canyons, dry washes and recent burn scars will be particularly dangerous after heavy rainfall, according to the National Weather Service.

Even without the excessive heat warning, it’s not exactly going to be cool in northern Utah for the rest of the week. But there are no triple-digit temperatures in the forecast, with highs in the mid-90s, and overnight lows in the upper 60s and low 70s in Salt Lake City. Patchy smoke from wildfires on the West Coast will continue Tuesday morning, and there’s a 20% chance of rain Tuesday afternoon and evening.

However, forecasters don’t think that precipitation will be enough to clear the smoke, and the Utah Division of Air Quality predicts air will remain “unhealthy for sensitive groups” along the Wasatch Front through Wednesday.

There’s was a 20% chance of rain in the St. George area Monday afternoon, rising to 30% Monday night and 40% Tuesday night. There’s a 20% chance of rain Wednesday afternoon, and a 20% chance of showers and thunderstorms, mostly before midnight, on Wednesday night.

The St. George area can expect highs of 102 to 106 through the weekend, with overnight lows from the low to mid-80s.

— Tribune reporter Paighten Harkins contributed to this story.

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