Abundant moisture in the atmosphere will combine with daytime heating, and large-scale lift ahead of an approaching area of low pressure to produce widespread thunderstorms over southern Colorado Monday and Tuesday.
Dewpoint temperatures early Monday morning range from the middle 40s in a few mountain locations to near 60 degrees near the Kansas line. Dewpoints above 55 are very significant in eastern Colorado.
Plentiful moisture also exists in the middle and upper levels of the atmosphere early this week. Early morning clouds indicate the presence of this moisture. In fact, enough instability was present a couple hours after sunrise on Monday that I was able to use several different pieces of data to monitor one of the first showers of the day.
While lift, instability and moisture are present, there isn’t enough wind shear present today to support widespread supercell thunderstorms. We are more likely to see storms develop in multi-cellular clusters. This type of storm development doesn’t often produce hail much larger than 1.5″ in diameter. Knowing this, and analyzing the severe weather ingredients today, hail near 1″ in diameter could briefly occur with the strongest storms. A number of storms may produce copious amounts of small hail. Get out the snow plows!
The greatest threat across the region today is for flash flooding. Storms will be very efficient rain producers in this moist environment and should only be moving about 20 mph during the afternoon and evening. Many of the storms may produce rain at a rate of more then 1/2″ per hour and some may produce more than an inch of rain in a very short period of time.
The flash flood risk is highest over the new burn scars (Hayden Pass, Junkins, Spring Fires) southwest of Pueblo where the soil is still not capable of absorbing water. If you live in a low lying spot in or near one of these burns, or downstream near one of the major waterways, you should remain alert early this week.
The typical trouble spots in urban areas are also at a flash flood risk. Locations that are low-lying, or those with poor drainage could have issues if a storm moves overhead.
This is a good time to remind you that you should never drive across a flooded road. Some vehicles will float in as little as a foot of water. The road may also be eroded beneath the water and it’s likely you won’t see it.
Things can change very fast too!
As an example, more than four inches of rain fell in the Ivywild neighborhood in southwest Colorado Springs June 16. While some of this was hail that took until Monday morning to melt, enough of it was rain that Fountain Creek near the Interstate just south of downtown Colorado Springs rose more than 4 feet in just 20 minutes!
Several intersections on the south side of Colorado Springs flooded at the same time and several other streets looked like raging rivers.
Look for storms to develop over the mountains between 10 a.m. and 1 p.m. Storms will then spread east through the afternoon and evening. It may take until the early morning hours of Tuesday before all the storms have moved out of the state or dissipated.
After a mid-day round of thunderstorms, it’s possible that the mountains and front range see some redevelopment at some point in the evening.