textproduct: Cheyenne

KEY MESSAGES

- Much cooler temperatures expected on Today and Monday behind a strong cold front.

- Strong winds will be possible Tuesday night into Wednesday morning across the western Nebraska Panhandle with a stout low-level jet expected to develop.

SHORT TERM /THROUGH MONDAY NIGHT/

Issued at 257 PM MDT Sun Sep 20 2026

Today will be the last day of consistently stormy weather across the area as the low pressure center spins over Casper, WY. Storms are already ongoing, thanks to the low pressure system pulling moist, southerly flow into the mid-levels out ahead of it. With cooler temperatures being observed today, that atmosphere is more stable, making strong to severe storms less likely later today. Hi-Res guidance still shows the potential for an isolated strong storm or two, but model soundings from the GFS show an environment with only about 500 to 700 J/kg of MUCAPE. This is enough instability to get thunderstorms, but not strong ones. Showers and storms will continue into the evening hours for locations in the Nebraska panhandle as the low pressure system slowly spins eastward into South Dakota. Once the system makes it east of the CWA, wrap around moisture could produce a few light showers overnight in the vicinity of the Pine Ridge from Lusk to Chadron.

As the trough/low pressure system moves eastward into the center of the country, shallow ridging will begin to build into the Rockies. As a result, temperatures on Monday will be a few degrees warmer compared to Sunday, but still cooler than average for this time of year. The ridge will also help clear clouds out of the area, lead to a partly to mostly sunny day across the forecast area. Precipitation chances are not anticipated, however, a few lingering showers will still be possible in the Pine Ridge area from the low pressure system moving out. Overnight, winds will turn southeasterly, ushering in low-level moisture with fog and low stratus potential in the Nebraska panhandle.

LONG TERM /TUESDAY THROUGH SUNDAY/

Issued at 257 PM MDT Sun Sep 20 2026

By Tuesday morning, there's is an area of high pressure that begins to form over the Great Lakes region as our former low pressure system enters the Northern plains causing a traffic jam over the east coast. This becomes our problem as the ridge builds over us it blocks the weak low pressure system off the west coast. Multiple shortwaves will be pushing through the Intermountain west with the first one starting late Tuesday evening through Wednesday morning for possible light rain showers. With the later timing off this wave its going to be hard to maintain higher energy levels needed for severe thunderstorms as the sun angle is slowly starting to decline. Wednesday afternoon through Thursday evening looks pretty dry as the Intermountain maintains southwest flow on the front edge of the ridge advecting in the dry airmass of the desert southwest. Thursday night into Friday morning another Low pressure system is progged to push into the Pacific Northwest to cause some light rain showers to possibly occur Friday. Daily high temperatures will fluctuate as 700mb temperatures bounce between 6 and 12 degrees C. So on our dry days expect temperatures to range between the 70's and low 80's to 60/70's on our rainy days. Overnight temperatures will remain relatively stable with the overnight lows to remain in the 40's to with some areas reaching the low 50's. This weekend is starting to trend warmer and drier with the global models wanting to amplify the ridging pattern over us shifting the potential Low pressure system from Friday further north into the Canadian Provinces.

AVIATION /00Z TAFS THROUGH 00Z TUESDAY/

Issued at 536 PM MDT Sun Sep 20 2026

VFR conditions expected over the next 24 hours for all Wyoming terminals; a mix of all flight categories expected over the next 24 hours for Nebraska terminals, with the exception of KSNY which should remain VFR through the period.

For Wyoming & KSNY - expect mid to high level clouds, with SCT to BKN status this evening before becoming FEW to SKC overnight into tomorrow. Breezy winds this evening will become 10 knots or less overnight through tomorrow.

For remaining Nebraska terminals - Mid to low level clouds continue this evening due to nearby showers and storms. These should clear later this evening, but then low clouds will overspread overnight through much of tomorrow morning alongside some lingering precipitation, but thunderstorm chances should be out of the region. All flight categories will continue to be possible with IFR to LIFR possible as the lowest clouds build in overnight, particularly for KCDR. Winds outside of any storms remaining near sites tonight will be 10 knots or less through the period.

CYS WATCHES/WARNINGS/ADVISORIES

WY...None. NE...None.