CHEYENNE – Forecasters at the National Weather Service say afternoon and evening thunderstorms will return to southeast Wyoming today with heavy rain a possibility by Friday, continuing through the weekend.
Aviva Braun, a meteorologist with the Cheyenne NWS office, said a higher than normal amount of moisture and instability in the atmosphere will bring the threat of heavy rain to the area Friday, Saturday and Sunday and possibly into the work week.
And that means the possibility of flash flooding in low-lying areas in Cheyenne, she said.
“The areas that are prone to flash flooding, I would make sure not to drive through those areas,” Braun said. “If you are driving and there’s a heavy rainstorm, stop and turn around. The phrasing we like to use is ‘Turn around, don’t drown.’”
Braun said it only takes 12 inches of water to move a vehicle.
She said meteorologists will issue watches and warnings as conditions warrant.
Cheyenne residents will see temperatures in the high 70s today, mid 70s Friday and high 60s Saturday and Sunday.
A flood warning is in effect for the North Platte River at Saratoga, which remains at high levels because of increased snowmelt over the past several days.
The NWS forecast Thursday morning showed the river reaching minor flood stage Saturday morning, but forecasters said increased chances for a rain-on-snow event from today on could cause the river to flood earlier and at higher levels than anticipated.
NWS said there is still substantial, very ripe snowpack at the 9,000- to 10,000-foot elevation range. Snowmelt runoff will increase through Friday as afternoon temperatures warm into the lower to mid-60s at 9,000-foot elevation.
Numerous afternoon mountain rain showers are forecast today through Saturday over the Laramie and Upper North Platte watersheds.
“We’re particularly concerned with the high terrain where we have a deep snowpack in some areas,” Braun said. “In addition to the heavy rain, you have snow melting at the same time. That becomes a larger threat than it would have been otherwise.”
Morning low temperatures at 9,000 feet will remain above the frost temperature of 37 degrees through Sunday, according to a NWS statement.
Increased runoff will also cause the Laramie River at Laramie to rise to flood flows by early next week. The Medicine Bow River near Elk Mountain may also see near flooding flows by the end of the weekend.
Forecasters expect a prolonged wet period Monday through Thursday of next week that will continue to keep the North Platte, Laramie and Medicine Bow rivers at moderate to high levels.
Graphical forecasts are available at: http://water.weather.gov/ahps2/index.php?wfo=cys.
Visit weather.gov/cheyenne and select the rivers and lakes tab for graphical forecasts and additional information.