FTB 08-02-2020: Flood Threat Increases along with the Severe Thunderstorm Threat

Issue Date: Sunday, August 2nd, 2020
Issue Time: 9:30AM MDT

— A MODERATE flood threat has been issued for Palmer Ridge, portions of the Southeast Plains, and the Spring Creek burn area

— A LOW flood threat has been issued for the Southeast Mountains, southern Front Range, southern Urban Corridor, Raton Ridge, and Decker burn area

Moderate rainfall and some thunder to start the morning over the SE Plains border counties. Behind the front that passed through yesterday, there’s quite a bit of moisture with dew points (more or less) greater than 50F present to the east of the green dashed line below. PW values have jumped back up to 0.75 inches in the Denver sounding, and easterly/southeasterly surface winds this afternoon and evening over the plains should help reinforce the low-level moisture over eastern Colorado.

With the large-scale trough moving onshore (Pacific Northwest), the ridge axis will be displaced to the east and help bring in some more mid-level energy into the state. Also, more shear is available this afternoon. Therefore, some stronger thunderstorms are expected over the eastern mountains with northwesterly flow helping spill them into the adjacent plains where they may become severe. Training storms will return the flood threat and the severe storms that develop, over the adjacent plains, will also be capable of producing large hail and strong outflow winds. Even though storm motion is expected to be 20-25 mph, there is increased likelihood storms will be able to produce a quick 0.50 inches over the Southeast Mountains near the Spring Creek burn area. A Moderate threat has been issued for this burn scar as well as over the Palmer Ridge. A Low flood threat has been issued for the adjacent plains and Southeast Mountains. Back to the west over the San Juan Mountains, rain rates should be low enough that they aren’t expected to cause flooding issues.

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:

Southeast Mountains, Palmer Ridge, Raton Ridge, Southeast Plains, Front Range, Urban Corridor, & Northeast Plains: 

Stronger storms are forecast with a severe thunderstorm threat over the Palmer Ridge, Southeast Plains, and Raton Ridge. Max 1-hour rain rates up to 1.5 inches will be possible with these stronger storms along with large hail and damaging outflow winds (up to 60 mph). Stay tuned into your local NWS office later today for the latest as a Moderate/Low flood threat has been issued. Over the mountains, storm totals up to 0.75 inches will be possible with higher rain rates over the southern Southeast Mountains when compared to the last couple of days. Thus, a Moderate flood threat has been issued for the Spring Creek burn area, but a Low flood threat should suffice for the Decker burn area as the set up isn’t quite as favorable for storm development over the area. Over the northern Front Range and Urban Corridor, more isolated storms are forecast with totals up to 0.6 inches possible.

Primetime: 1PM to 1AM

San Juan Mountains, Central Mountains, San Luis Valley, Northern Mountains, Southwest Slope, Northwest Slope, & Grand Valley:

More widespread storm activity is expected over the southern/eastern San Juan Mountains with more isolated storms over the western San Juan Mountains. Higher rain rates are expected east (0.6 inches) with more wind anticipated west and to the north over the Central Mountains. Isolated storm totals up to 0.25 inches (south) will still be possible, but further north, more cloud cover and sprinkles are forecast. Steering flow could push some of this rain into the western San Luis Valley with totals up to 0.15 inches possible by morning. Flooding is not forecast. It’s also quite hot over Grand Valley already (orange circle in the surface map), so hitting the century mark again is forecast.

Primetime: 1PM to 8PM