As storm brews, some states face ‘most dangerous flash flooding risk in last 5 years’

The highest elevations of the Colorado Rockies are expected to witness one of the earliest snow events of the season, according to forecasters from the National Weather Service (NWS). The event will be part of an upcoming storm that is likely to bring heavy rainfall to the Southwest and central US.

"Pacific tropical moisture will wrap into a storm over the southwest U.S. and will continue a multi-day heavy rainfall event this week that will extend into the Midwest and southern Plains," the NWS said in an update.

Where is flash flooding possible?

The system has been described as a "hybrid storm" as it combines the remnants of Hurricane Polo with a separate and extensive weather system. The storm is forecast to bring heavy rainfall and significant flooding from Arizona to Chicago over the coming few days.

"Considerable flash flooding is possible across portions of New Mexico and west Texas today through Wednesday," the weather service said in a post on social media. AccuWeather's chief meteorologist Jon Porter said: "In some places, especially in New Mexico, this may be the most dangerous flash flooding risk in the last 5 years or more."

Where is snow coming?

In the upcoming storm, snow levels look to be above 11,000 feet, meaning that only lightly-populated regions are likely to see snow. Most parts of the state, including the Denver area, will only get rain. Meanwhile, in southern Colorado, the weather service in Pueblo said: "Snow levels look to remain high; above 12,000 feet through this period. Several inches of snow are possible across the higher peaks."

Maps issued by the weather office in Pueblo suggest that up to 8 inches of snow could be seen in the Sangre de Cristo Mountains, near Westcliffe and south of La Veta Pass toward Trinidad. In Denver, weather service maps show that some spots west of the city could be buried in 8 inches of snow in a high-end scenario. The storm, which is coming together as of Tuesday (September 29), is expected to hit by the end of the month.

Driving conditions to be hit

The snow storm could cause driving troubles for people in southern Colorado. Monarch, Wolf Creek, and La Veta passes all fall inside the shaded areas on the Pueblo map, according to the automotive news website Autoblog. "Wet snow on those passes is most likely to turn icy overnight and early in the morning," the website said.