Utah forecast: Cycle of thunderstorms brings Flash Flood Watch for most of state

Debris and water cover the ground after a flash flood Monday, Sept. 14, 2015, in Hildale, Utah. Authorities say multiple people are dead and others missing after a flash flood ripped through the town on the Utah-Arizona border Monday night. (Mark Lamont via AP) MANDATORY CREDIT

Most of Utah, with the exception of the northern Wasatch Front, was under a Flash Flood Watch through Tuesday night.

The thunderstorms and rain clouds hovering over the state were the result of monsoonal moisture trapped between a upper-atmospheric, southwesterly flow out of Northern California and another ridge of air from the southern High Plains.

From eastern Utah's Duchesne and Uintah counties south to Arizona border, west through southern Utah to the Nevada state line, and then north to Utah County and central Utah's Delta area, the National Weather Service warned that occasionally heavy rain could trigger sudden flooding in the region's slot canyons, waterways and on mountain slopes recently denuded by wildfires.

The wet weather pattern was expected to gradually ease on Wednesday, and will begin to exit eastward through the northern Rockies on Thursday.

Initially, at least, the Salt Lake and Tooele valleys were not in the Flash Flood Watch area, but numerous rain showers were nonetheless on tap through Wednesday. The cloud cover brought higher humidity and cooler temperatures, with highs on Wednesday expected to be in the upper-80s, up a few degrees from Tuesday's forecast.

However, southern Utah's storm clouds are heavy with rain, with more than an inch of rainfall having already fallen in Washington County over a 24-hour period as of Tuesday morning. Enterprise reported 1.49 inches, St. George 1.19, and almost an inch in Cedar City.

Wednesday will dawn partly sunny in Utah's Dixie, but fresh cycle of rainfall was forecast to arrive as noon approached. High temperatures Wednesday in the St. George area will be in the mid-80s, up about 5 degrees from Tuesday.

The moisture-laden storms will ease pollution a bit. The Utah Division of Air Quality forecast mostly "green," or healthy conditions by the midweek, though Salt Lake, Davis, Weber and Box Elder counties remained in the "yellow," or moderate range for ozone and particulate levels.

The Intermountain Allergy & Asthma website rated only mold as elevated on its pollen index as of Tuesday, and then only at "moderate" levels. All other allergens were "low," or did not register.

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


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