Widespread rain is expected to continue through early Friday, October 24, according to the National Weather Service in Grand Junction. The region faces an increased potential for flooding today and Friday, particularly in portions of southeast Utah and southwest Colorado.
Strong to severe thunderstorms are possible favoring southeastern Utah and far western Colorado generally from I-70 south through tonight, October 22. Rainfall amounts in the southern mountains range from 1 to 3 inches, with higher amounts of 2 to 4 inches or more possible in the San Juans and southern foothills. A flood watch is in effect through Friday morning for portions of Utah, specifically UTZ022-027 and UTZ028-029.
The potential for flash flooding is elevated due to saturated soil from previous rainfall. Localized heavy rain in showers and thunderstorms is likely, especially near steep terrain, slot canyons, and recent fire scars. In the San Juans and adjacent southerly valleys, there is a moderate risk of excessive rainfall, with precipitation totals of 2 to 4 inches possible, though totals of 4 to 5 inches are possible in parts of the southern San Juans. This precipitation is expected to fall overnight through early Friday morning, October 24.
Hydrologists noted that rain-on-snow could lead to additional runoff and a rapid rise in many creeks, streams, and rivers. Models suggest several rivers could reach bankfull or higher at river forecast points across southwest Colorado and southeast Utah. There is high confidence in minor flooding and related impacts along the San Juan, Piedra, Animas, and La Plata Rivers, as well as above Vallecito Reservoir.
A deep trough off the West Coast and high pressure near Big Bend are driving a strong south to southwesterly flow that is advecting subtropical moisture into eastern Utah and western Colorado. While a second shortwave system is expected to move in Friday night and continue through the weekend, models diverge on the timing and track of that system by Sunday, with some solutions tracking it to the west over northern Utah.
