Southwest Colorado’s wet spring should continue, with a rainy Memorial Day expected. Also, June, typically the region’s driest month, will likely to see more rain than normal.
Kris Sanders, meteorologist with the National Weather Service in Grand Junction, said clouds should begin building Memorial Day around noon, give or take an hour, and intermittent rainfall is expected in Durango and Cortez and at lower elevations.
Rain will vary from a trace to 0.1-inch – depending on the strength of the localized rainfall, Sanders said.
“There’s a chance you could see some rain Sunday night in Durango, but the main show gets going around noon Monday,” he said.
Lisa Schwantes, spokeswoman with the Colorado Department of Transportation, said Monday’s rain could delay work on Colorado Highway 145 near mile marker 21, where two two-story tall boulders fell Friday from a ridge above the highway, forcing a closure that remains in place.
Silverton and Telluride can expect snowfall on Memorial Day, and like lower elevations, the mountain towns can expect a couple waves of snowfall during the day.
Above 9,000 feet in the San Juan Mountains, Sanders said the National Weather Service expects 4 to 6 inches of snowfall.
Low temperatures in the high country are expected to be in the low 20s on Monday and Tuesday nights, with lows in Silverton expected to reach 23 Monday night and 24 Tuesday night. Telluride nighttime lows are expected to be about 1 degree warmer compared with Silverton. In Cortez, lows were expected to dip into the lower to mid-30s on Monday night.
Efforts to clear Colorado 145 continued through the weekend, but Monday’s rains could delay work.
By Sunday, crews had finished scaling the top of the ridge to ensure it was stable and no further rock slides were probable, Schwantes said.
An earthwork ramp had to be built to the top of the boulder on the highway to drill holes to place explosives so it could be “boulder blasted” into smaller rock for removal, she said.
It is unclear how long work to clear the boulders will take to be completed.
“There are a lot of unknowns right now. We don’t know how long it will take to drill the holes, and then we have to remove the rubble, and the rain could delay things,” she said.
Crews are also building a temporary, dirt bypass road so the highway can be reopened to alternating, one-lane northbound and southbound traffic. The temporary road could open Wednesday, possibly even Tuesday, unless unforeseen problems crop up, Schwantes said.
The boulder sitting on the highway is 48 feet long, 18 feet wide and 18 feet high and weighs about 2.3 million pounds. The other boulder, which is 50 feet long, 50 feet wide and 26 feet high and weighs 8.5 million pounds, tumbled across the highway slicing an 8-foot trench through the asphalt and road base.
Continuing wet weather could cause other rock slides across sections of highways adjacent to ridges and cliffs, and Schwantes said travelers should let CDOT know if they see rocks falling across highways.
In June, an El Niño pattern is expected to keep precipitation above-average and temperatures below-average for Southwest Colorado.
Sanders said Durango’s average rainfall in June is only 0.01 of an inch, a low bar that should be a fairly easy to beat with an El Niño entrenched.
The National Weather Service lists a 70 percent chance that the El Niño pattern, which favors above-average precipitation in Southwest Colorado, will extend through summer.
Sanders said the monsoon period for Southwest Colorado typically begins in mid-July, but during an El Niño the monsoon’s onset can be delayed. However, it may be hard to notice if El Niño continues to bring frequent spring rains.
parmijo@durangoherald.com