FTB 06-01-2020: Rainfall Chances Increase Over the Southern Mountains to Start Meteorological Summer

Issue Date: Monday, June 1st, 2020
Issue Time: 9AM MDT

— A LOW flood threat has been issued for the Decker and Spring Creek burn areas

There’s a bit of cloud cover over the state to start the morning, but visible satellite is already showing those clouds breaking up over the eastern plains. By looking at the water vapor imagery below, it looks like moisture is a little weaker in this area as compared to the northwest corner of the state where moisture and lift is a bit stronger. This means it will likely take a bit longer for the sun to shine through over this region. The best moisture remains over areas with the green “X”, but PW remains high at Grand Junction and Denver around 0.70 inches. That means there should be plenty of moisture for another round of diurnally driven storms this afternoon with residual moisture under the ridging pattern to start meteorological summer.

Today’s pattern generally looks the same as Sunday. Westerly flow aloft will continue, but it is expected to weaken, which means there will be little to no steering flow. This will cause storms to be nearly stationary and pulse in place with little upper air dynamics to make them severe. Additionally, this afternoon looks to have a little more widespread rainfall activity that yesterday with storms favoring the areas along and near the Continental Divide in the southern Front Range, Central Mountains, Southeast Mountains and San Juan Mountains. Storms are also likely to form over the western Palmer and Raton Ridge, but activity will likely decrease when compared to yesterday. Accumulations should also be on the upswing with the steering flow so weak. With the Southeast Mountains expecting to have more rainfall activity this afternoon, the Low flood threat has been re-issued for the Decker and Spring Creek burn areas. Elsewhere, rain rates are forecast to be low enough that flooding issues should be avoided.

Today’s Flood Threat Map

For more information on today’s flood threat, see the map below. If there is a threat, hover over the threat areas for more details, and click on burn areas to learn more about them. For Zone-Specific forecasts, scroll below the threat map.

Zone-Specific Forecasts:

Front Range, Southeast Mountains, San Juan Mountains, & Central Mountains:

Over western Colorado, storms look to favor the eastern Central Mountains and San Juan Mountains. It looks to be most active further south, which includes increased activity over the Southeast Mountains. Max 1-hour rain rates up to 0.65 inches will be possible over the eastern San Juan Mountains with 1-hour rain rates just over 0.50 inches possible over the Southeast Mountains. This is shaping up to be a nice wetting rain for that drought area in the San Juans. Further north into central Colorado, max 1-hour rain rates up to 0.50 inches will be possible along and near the Divide. A couple stronger storms may produce some brief gusty winds and small hail. Storms should start to end a couple hours after sundown when instability decreases.

These rain rates will be strong enough to cause flash flooding issues over recent burn areas in the Southeast Mountains if storms form directly overhead. Thus, a Low flood threat has been issued for the Decker and Spring Creek burn areas. Threats include local stream flooding, mud flows and debris slides. Note that we have yet to see what flash flooding looks like near and around the Decker burn area, and what rain rates will cause issues for the area. Please exercise extreme caution if you’re participating in recreation near the burn scar.

Primetime: 1PM to 11PM

Raton Ridge, San Luis Valley, Palmer Ridge, Southeast Plains, Urban Corridor, Palmer Ridge, & Northeast Plains:

Enhanced convergence along the western Palmer and Raton Ridge may produce some afternoon storms. Max 1-hour rain rates up to 0.50 inches will be possible with most storms producing virga and total rainfall under 0.25 inches. The edges of the San Luis Valley may also get a little rainfall with totals up to 0.20 inches possible by morning. There is the possibility of some weak rainfall over the Northeast Plains tonight, but totals should remain under 0.25 inches.

Primetime: 1PM to 12AM

Northern Mountains, Northwest Slope, Grand Valley, & Southwest Slope:

Looks to remain hot and dry for these regions, especially north. High temperatures over the lower elevations looks to reach the upper 80Fs and 90Fs, so the increase in afternoon cloud cover will be welcomed. There is a chance for some storms to move in from the southeast (around the high) into the southwest corner of the state, but storms should dissipate quickly as they move off the high terrains and into drier air.