CHEYENNE – Monsoonal moisture in place over southeast Wyoming could help bring afternoon and evening showers and thunderstorms, some possibly strong or severe, to the area today and Sunday.

National Weather Service forecasters expect thunderstorm coverage to increase today, especially along and east of Interstate 25.

In Cheyenne, expect high temperatures to warm into the low 80s.

A chance of thunderstorms remains in the forecast tonight with a low expected in the mid-50s.

The eastern parts of Laramie and Goshen counties are under a marginal threat for severe weather today, according to the NWS Storm Prediction Center in its Friday forecast.

Crystal Worley, a meteorologist with the National Weather Service in Cheyenne, explained that a monsoon is a seasonal change in the direction of air flow, bringing moist air northward from the Gulf of Mexico and the Pacific Ocean. It usually takes place during the summer months of July, August and September.

“The flow starts to come from the Southwest,” Worley said. “That flow is not limited to the southwest portion of the United States – Arizona, New Mexico, Nevada. It can affect things farther north as well.”

Sunday could see a variety of weather activity in southeast Wyoming.

Meteorologists expect a strong upper level low pressure system to move through the area Sunday afternoon that could bring all the ingredients together – moisture, lift, instability and shear – for a fairly widespread severe thunderstorm event.

“That’s going to provide some forcing for storms,” Worley said. “You can’t just have moisture. You need something to force that moisture up into the upper levels to form thunderstorms.”

Supercell thunderstorms are looking more likely for Sunday, which could produce all modes of severe weather. Heavy rainfall could lead to some flash flooding.

“It looks like some pretty good ingredients will be in place for some hail and damaging winds as well,” she said.

Cheyenne and the western part of Laramie County are under a marginal risk for severe weather Sunday, according to the Storm Prediction Center, while the eastern parts of Laramie and Platte counties and Goshen County are under a slight risk.

Expect high temperatures to reach the low 80s on Sunday in Cheyenne.

Those with outdoor plans this weekend should monitor weather forecasts for the latest updates.

“It’s always good to be weather-aware, especially when the Storm Prediction Center is highlighting it,” Worley said. “It would be good for people to go to our website or SPC’s website to make sure they have the most up-to-date information. Make sure that weather radios are good to go or have some other way to get watch, warning and forecast information.”

Isolated late-day thunderstorms are possible Tuesday through Thursday.

Steve Knight is the Wyoming Tribune Eagle’s local government reporter. He can be reached at 307-633-3182 or

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