The storms that lingered along Colorado's Front Range in recent days brought plenty of rain and hail to the region, raising river and creek levels in the north, and prompted a flash flood advisory over the Waldo Canyon burn scar Sunday.
The Cache la Poudre River in northern Colorado threatened to spill over its banks on Sunday, reaching 7.9 feet - just shy of the 8-foot flood stage, the National Weather Service in Boulder said. Greeley police closed 71st Avenue at the river because of some flooding, and parks and trails near the river also were closed, the City of Greeley said in a release.
The weather service said the river could rise to nearly 8.5 feet by early Tuesday, but is expected fall below flood stage by Wednesday. Other creeks and rivers also were running high, but flooding was not expected.
But what happens all depends on whether there's more rain, and how fast snowmelt runoff flows into the river.
The rise in river levels is common during May, Colorado's wettest month, according to weather service meteorologist Kyle Fredin in Boulder.
"Snowmelt runoff during begins in May like clockwork around here," Fredin said. "We haven't observed any overflowing of river banks at this time, but we're paying close attention to any areas where the river levels may be higher than normal to keep the public informed."
The weather service is also watching areas that got a significant amount of rain, because saturated ground plus additional excess rain could prompt flood warnings, Fredin said. In west Loveland, for example, up to 4 inches of rain fell Friday night and although flooding was reported only at some intersections, meteorologists will watch the area closely if another storm hits, Fredin explained.
May's storms have followed typical a typical pattern of developing throughout the day with precipitation begining in the afternoon or evening hours, according to meteorologist Jennifer Stark in Pueblo,
"Upper-low pressure systems have been moving in from the south and southwest, carrying lots of moisture and tropical-like weather. The colder fronts in the mountains slow down the storm systems and give them time to develop and grow," Stark said.
A flash flood warning briefly closed U.S. 24 from Cascade to Cave of the Winds near Manitou Springs Sunday, and there were reports of 2 inches of hail at Palmer Lake, according to the weather service.
A small stream flood advisory was in effect for west-central El Paso County from mid-afternoon until 6 p.m. Sunday as a storm moved over the Waldo Canyon burn scar. In Divide, weather spotters reported 1.25 inches of rain in less than an hour, while about 1.5 inches of rain fell over Penrose in El Paso County.
The storms weakened quickly and did not cause the street and small stream flooding Manitou Springs wrestled with Friday.
"One of the things we remain aware of is where we've seen more rainfall, because we know there will be issues with ground saturation and run-off," Stark said. "It's a situational awareness, for any areas that we know are flood-prone, especially in burn scars with poor soils that don't handle rain very well."
The Memorial Day forecast called for a slight chance of showers between 11 a.m. and noon, with a continuing 20 percent chance of rain and thunderstorms in the afternoon. Partly sunny skies with a daytime high of 72 and calm winds could be possible, with temperatures dropping to the low 50s overnight and new rainfall amounts of less than a tenth of an inch, the weather service predicted.
Drier and warmer conditions could develop Tuesday and Wednesday, with expected highs in the upper 70s to low 80s and slightly breezy, while another round of showers and storms could roll into the region by Thursday, the weather service said.