Water content of Colorado’s snowpack raises flood concerns
DENVER (AP) — Forecasters are anywhere from concerned to alarmed about the potential for flooding in Colorado’s high country as the water content of the state’s snowpack reaches very high levels, from 324% of normal in the South Platte drainage basin above Denver to 728% of normal in the San Juan Mountains.
The snow water equivalent, or SWE, of snowpack in the mountains peaked at 20.5 inches (52 centimeters) on April 15, but was still at about 16.5 inches (41.9 centimeters) on Thursday, according to the National Weather Service in Boulder.
“I wouldn’t say go out and get ready for a massive flood, but getting prepared is a good idea,” NWS meteorologist Natalie Sullivan said Friday. “These levels are definitely something to keep an eye on, but it is not overly alarming.”
The SWE of 16.5 inches is more than three times higher than the normal for May 30, which is more typically 4.5 inches (11.4 centimeters) to 6 inches (15.2 centimeters), according to the National Weather Service. The variations in normal levels are attributable to different areas of Colorado.
SWE readings are still significantly lower than years when huge floods killed people and destroyed property, including in 1995 when the SWE was 514% and 2011 when it was 499% in the Colorado’s north-central mountains, Sullivan said.
Above-normal spring precipitation and below-normal temperatures have allowed snowpacks in the Colorado Rockies to remain high this year, the weather service said.
Another factor that raises concern is that temperatures are forecast to rise to the mid-80s next week in the Denver metro area and into the 90s in southwest Colorado, where authorities in small towns have bigger flooding concerns, NWS meteorologist Dave Barjenbruch told The Denver Post.
With days getting longer and temperatures across Colorado rising to above normal next week, flooding is a real possibility, Barjenbruch said. For example, the temperature in Denver is forecast to reach 84 degrees (28.8 Celsius) on Monday, which is 6 degrees above normal, after three weeks of temperatures well below normal, Barjenbruch said.
“What that is telling us is there is an awful lot of snow in the mountains, especially above 10,000 feet (3,048 meters). That will accelerate the snowmelt. We’re going to be melting it off quite fast in the next two weeks,” Barjenbruch said.
There is cause for concern about flooding in mountain towns in the north-central mountains, but real alarm in the San Juan Mountains of southwest Colorado, he said.
The trouble is, there isn’t a lot of historical data about how serious the situation is in southern Colorado because usually there isn’t a lot of snow in the San Juans by June, Barjenbruch said. This year, the snowpack in the area is at 728 percent of normal, an alarming level, he said.
With warm temperatures next week, 2 inches (5 centimeters) of water could be melting off the snowpack a day, which is like getting 2 inches of rainfall a day.
Weather watchers are paying close attention to small towns near creeks and springs in the San Juan Mountains, Barjenbruch said.
Information from: The Denver Post, http://www.denverpost.com