A blast of moisture that soaked a wide swath of Southwest Colorado this week is likely the last bit of monsoonal moisture, as less daylight and cooler temperatures will soon put a stop to the annual weather pattern.
“I think monsoon season is kind of on the way out,” said Mark Miller, meteorologist with the National Weather Service in Grand Junction, on Wednesday.
A widespread storm dumped about an inch of moisture on most parts of Montezuma, La Plata and Archuleta counties Sunday through Wednesday, he said.
Moisture totals during the four days included:
- 1.22 inches 1.2 miles southwest of Cortez.
- 0.93 inches at the Cortez Municipal Airport.
- 1.26 inches 1 mile east, southeast of Durango.
- 0.88 inches in downtown Durango.
- 0.92 near downtown Durango.
- 1.36 inches 4.8 miles west, southwest of Durango.
- 1.67 inches 7 miles northwest of Ignacio.
- 1.06 inches 7 miles north of Bayfield.
- 0.46 inches a half mile south, southeast of Pagosa Springs.
- 1.02 inches 5 miles north, northwest of Pagosa Springs.
“Overall, it looks like anywhere from half an inch all the way up to an inch and a half over the last several days dating back to Sunday,” he said. “It definitely looks pretty uniform, which is kind of surprising. Typically with these setups, you get some real big winners and some places that didn’t do so well.”
The storms were expected to stick around into Friday before pushing out for the weekend, he said. It is hit-and-miss as to whether the lingering storms will produce any significant rainfall.
“I'd probably bank on there being less (rain) than what we've seen the last few days, but still there's that potential there,” Miller said. “If you have a pretty decent cell that happens to go over you, it can certainly put down a quick half inch to even up to an inch in spots.”
The next decent chance for moisture arrives the middle of next week, he said.
“Maybe that can produce some additional shower activity, but it doesn't look too active, at least compared to this last week,” Miller said.
He said the moisture that moved through the region this week came from the south, including the Gulf of Mexico. By contrast, the moisture expected to arrive next week, if it does arrive, will drop in from the north and west, he said.
Miller said monsoons typically wrap up by mid-September. It is not so much a date on the calendar as it is a lack of sunlight and cooler temperatures that bring an end to the monsoons, he said.
“The sun's getting lower in the sky, so you're not heating as much of the surface like typically in July and August when the sun's really high and you're baking the ground and you get these showers and storms that just explode off the terrain,” Miller explained. “It's starting to get a little bit cooler out – that just kind of takes the juice out of the monsoon season.”
Weather forecasters are calling for an El Nino weather pattern this winter. Typically, El Nino bring below-average moisture amounts in northern parts of the United States. But the jet stream can be more active across the southern tier of the United States, which can benefit the San Juan Mountains in Southwest Colorado.
But it is unpredictable, Miller said. Last year, a La Nina delivered above-average snow totals to the San Juan Mountains, he said.
“It really does depend on the pattern that sets up and if that has any kind of staying power,” Miller said. “That can drive the entire season.”