The National Weather Service on Sunday night issued a flood advisory for Montezuma and Dolores counties, warning about potential flooding in low-lying areas and normally dry arroyos.
The advisory came after weather watchers reported heavy rainfall that quickly dumped 1 to 1.5 inches in the area. The flood advisory is in effect from 6:38 p.m. to 9:30 p.m. Sunday.
“Minor flooding is ongoing or expected to begin shortly,” the weather service said. Affected areas included Cortez, Mancos, Dolores, Dove Creek, Rico, Lebanon, Lewis, Arriola, Yellow Jacket, Cahone, Stoner, Towaoc and Dunton.
The evening rain came on the heels of earlier precipitation Sunday, which by 5:55 p.m. had totaled 0.48 inch within six hours, according to the weather service.
Experts said the storms marked the start of the monsoon season in Southwest Colorado.
“There’s no question the monsoon season has started. For the monsoon, you have to have high pressure in a specific location that draws in this moisture. You tend to have low pressure off the coast, and it brings in all this moisture,” said NWS meteorologist Tom Renwick.
In Durango, the rainy June continued this week, with 0.67 inch of rain by noon Sunday, bringing the month’s total to about 1.25 inches, according to the National Weather Service.
The weather service’s Advanced Hydrologic Prediction Service measured 1.5 to 2 inches in north La Plata County.
Pagosa Springs has also witnessed a soggy few days, receiving 1.19 inches and amounting to 1.36 inches in June.
The National Weather Service forecast calls for a chance of thunderstorms throughout the new week. However, along with the benefit of rain, the storms bring a threat of wildfire.
“Where we really struggle with lightning is what we call ‘lightning holdovers,’” said Durango Fire Chief Hal Doughty. “This is where a tree gets struck by lightning, and then it kind of just sits there, and it may be still hot or smoldering. But then two or three days later, the wind picks up, and it’s dry again.”
Renwick said there is strong possibility of rain Thursday. By the weekend, the storm likely will move into the northern San Juan Mountains.
“It looks like Tuesday and Wednesday are sort of down days. But then high pressure sets up over Texas again, which is what we want for monsoonal moisture. So I would say more widespread precipitation on Thursday,” Renwick said.
On Thursday, La Plata County and San Juan National Forest Service tweeted that fire restrictions had been reduced to Stage 1. However, a lack of precipitation in parts of La Plata County was still a concern for fire officials.
“Conditions are probably improving fairly rapidly. But, there's some areas of the county that have experienced very little rainfall with the storms we’ve had,” Doughty said.
Fire managers will evaluate fire fuels and weather conditions throughout the week.
To estimate the threat of wildfires, Doughty said, officials look more at the moisture content of vegetation, than the amount of new precipitation. High fuel moisture means less risk of fire.
Fuel moisture is measured by weighing a dead fuel sample, such as a stick, cooking the sample, then measuring the weight of the sample again. The difference in weight determines the sample’s amount of moisture.
“The most hazardous fuels for us are the light fuels like grasses and things like that because if a fire starts, the fire can travel through those very quickly,” Doughty said.
Small fuels, such as small sticks and grass, are considered 10-hour fuels, while fallen trees are considered 1,000-hour fuels. The smaller the time frame, the more responsive the plants are to changing weather conditions, Doughty said. Officials check fuel moisture content weekly to determine the potential for fire danger.
By evaluating 1,000-hour fuels, officials can estimate how certain trees will burn., Doughty said. Although larger fuels take longer to ignite because of their volume, they have much more energy once on fire. Smaller fuels can spread quickly but have less energy.
Fire officials are still examining the amount of fuels in live trees as well as the amount of moisture in dead fuels. Doughty said moisture levels might take a while to recover.
tbrown@durangoherald.com
