Thunderstorms capable of producing heavy rain and flash flooding were expected to be possible in central Utah, particularly east of the I-15 corridor and south of I-80. In a notice issued by the National Weather Service Salt Lake City, a Flood Watch was placed in effect for several areas through Monday evening.
The weather pattern involves a deepening PacNW trough that has helped strengthen a Pacific moisture tap. This has resulted in widespread precipitation values in excess of 1 inch across much of Utah, which is approximately 150-200% of the climatological normal for late August. The combination of moisture and strong deep layer flow has previously yielded strong to severe thunderstorms with heavy rain and flash flooding.
Forecast details indicated that while some drier air might shift into Utah from the west, moisture would remain positioned across eastern Utah and southwest Wyoming. This area, including much of the region east of I-15 and south of I-80, was identified as having a slight risk for excessive rainfall. Other areas throughout Utah, excluding the far west and northwest, were noted as having a marginal risk of excessive rainfall.
In addition to rainfall risks, isolated thunderstorms could become strong to severe, bringing the potential for strong winds and hail. Even as a drying trend is expected to begin Tuesday, moisture may linger enough to allow for the development of showers and thunderstorms on a day-to-day basis.
The National Weather Service noted that saturated soils and existing high water levels could exacerbate the potential for flash flooding as multiple days of repeat thunderstorms occur. While a general drying trend was expected to begin Tuesday, the threat of localized heavy rain in rain-sensitive basins remained a concern.
