Severe Storms, Drenching Downpours March Through Rockies, Dakotas

Thunderstorms are producing drenching downpours across the Rockies today, with a few of them becoming severe.

The stormy weather is part of a strong push of monsoonal moisture moving from the Pacific tropics into the Southwest. It is squeezing out that moisture as rain and thunderstorms, quickly filling normally dry washes.

A Flood Watch stretches from south-central Arizona across southwestern Utah and western Colorado. This includes Tucson and Phoenix, Ariz., Grand Canyon and Bryce Canyon national parks, and Grand Junction, Colo.

The very heavy rainfall is producing 1 to 2 inches of rain in the space of an hour, and with repetitive storms crossing the region over the next couple of days, could lead to rainfall totals of 2 to 5 inches through Tuesday. Remember, if you come across water in the road or on a trail, do not attempt to cross it as it is likely deeper than it appears. “Turn Around, Don’t Drown!”

More than 20 people may be missing after flash flooding hit the Bright Angel Canyon part of Grand Canyon National Park on Saturday. With additional rain in the area, use extreme caution over the next few days.

Meanwhile, the moisture is continuing to advance northward into the northern Plains, where a cold front is squeezing it out as severe thunderstorms. A Severe Thunderstorm Watch is in place for western and central North Dakota, eastern Montana, northern South Dakota and adjacent parts of Wyoming.

The primary threat with any of these storms will be large hail, although damaging winds are possible as well.

In addition to the storm threat over the Dakotas and Montana, which is also considered to be a Slight Risk (level 2 out of 5 on the severe storm scale) for severe weather, there is a broad area of Marginal Risk (level 1 out of 5) in southern Arizona as well as from Utah to western Kansas and across the Dakotas. This includes much of the I-25 corridor including Denver and Cheyenne, Wyo.