textproduct: Cheyenne

KEY MESSAGES

- Above average temperatures will continue through the end of the week, but a weekend system will drop temperatures towards near to below-average.

- Precipitation possible Friday through Sunday, with the potential for frozen precipitation outside of the mountains on Sunday.

- Some clearing and warming back to near normal temperatures next week, with some low end precipitation chances mostly in the high terrain.

SHORT TERM /THROUGH THURSDAY NIGHT/

Issued at 230 PM MDT Wed Oct 21 2026

The overall pattern through Thursday night should remain largely unchanged as our region will sit between two stout systems, with a deep upper level ridge over the Central US, and a deep upper level Pacific low moving inland and then slowly northeastwards. This will continue to produce a southwesterly flow that will increase moisture across the region, particularly later into Thursday and moving into the weekend. For the rest of this evening and overnight, increasing cloudiness is seen on satellite primarily across Carbon and Albany Counties where the highest influx of moisture is moving in for the day. We could see a few light showers across this area, and some earlier runs of CAMs were producing even a weak echo as far east as Laramie County, but overall probabilities are on the low side alongside low confidence.

Cloudiness will overspread the region on Thursday though as the moisture continues to increase. While this could impact afternoon highs for the western half of the forecast area, 700 mb temperatures remain at around 7-10 C which should encourage highs similar to today in the 60's to 70's. CAMs are much more excited for precipitation extending out of the high terrain tomorrow afternoon and evening, with a chance of showers across much of the I-80 corridor through Nebraska. While storm chances are largely declining as we enter the cold season, a brief swath of CAPE around 200-300 J/kg across Carbon County could encourage a rumble of thunder or two, but don't expect much out of this activity. Otherwise cloudiness should linger through the nighttime hours which will allow for overnight lows to remain on the warm side due to insulation, with upper 40's to 50's across eastern Wyoming and the Nebraska panhandle as we move into the weekend.

LONG TERM /FRIDAY THROUGH WEDNESDAY/

Issued at 230 PM MDT Wed Oct 21 2026

On Friday the upper level Pacific system will be approaching from the southwest. Ahead of it a few impulses of mid and low level vorticity are progged to pass over the area, allowing showers to exist over mostly the intermountain areas. In addition, a jet streak of about 80-100 knots intensifies ahead of the system. The phase of the jet and impulses are somewhat mistimed to allow for more widespread precipitation. The jet will suppress the development of precipitation due to a healthy amount of positive omega below 500 mbar. The exceptions are in the Nebraska Panhandle where the entrance region of the jet may be more favorable. It also helps that this region will have more moisture and instability to work with. Skew-T profiles have about 500 MUCAPE and 60 knots of speed shear to perhaps prop up a few thunderstorms at and after peak daytime heating. No severe weather is anticipated with any storm, though small hail is a probability given the shear. The clearing cloud coverage to the east allows much of the Panhandle to reach the mid 70 to low 80s in the afternoon. Moving west, the cloud coverage increases, only allowing southeast Wyoming to make it into the mid 60s to low 70s. Overnight a cold front is expected to make its way southeast through the area. A 10 degree drop from Thursday overnight lows is likely, with lows in the mid 30s to low 40s.

Returning to the upper level system to our west. The evolution through Friday is for the trough to split and elongate. The northern portion gets picked up by a strong negatively tilted trough in Canada, while the southern end of the trough remains over the southwest. This southern lobe of the system will be the driver of more exciting weather going into Sunday and Monday.

Post front Saturday is anticipated to be breezy and partly to mostly cloudy. Winds behind the front could be fresh with gusts to 40 mph possible. A few showers are possible as they drift north from the advection activity in Colorado, but otherwise a dry day. Temperatures struggle to make it to 60, with most of us staying in the 50s. Sunday the remaining Pacific system moves northeast bringing with it more chances for precipitation. The GFS is picking up on a possible TROWL setting up over our northern counties. Temperatures are marginal for any accumulation of snow, but a mix of snow and rain at the surface is possible. At our peaks an inch or two of snow may be possible.

Following the system a ridge builds in behind it. Clearing skies and a gradual warming trend. The next storm system is being advertised in the GFS, however there are significant run to run variability in the timing and positioning of this system. The ECMWF is telling a similar story, although the system is much flatter and slower. Precipitation chances would be on the lower side with this system with not much synoptically to refill the moisture reserve ahead of the trough and not much attendant with the airmass associated with it.

AVIATION /00Z TAFS THROUGH 00Z FRIDAY/

Issued at 527 PM MDT Wed Oct 21 2026

Breezy conditions are expected overnight into tomorrow in response to a 25-30 SW 700 mb jet ejecting ahead of a closed low located off the coast of California. Can expected gusts up to 25 knots out of the south, mainly for KRWL and KCDR with mainly dry conditions. High- resolution guidance along with forecast soundings are hinting at considerable low-level moistening, so have included MVFR CIGs for KSNY, KAIA, and KBFF. Moderate confidence this will occur primarily after 10Z where wind speeds are also expected to be rather light under some mid and high level clouds, allowing for effective radiative cooling. Introduced a PROB30 group for KRWL after 21Z as CAMs have been consistent in showing the onset of -SHRA ahead of our next system, with the most widespread activity expected to occur after 00Z Friday.

CYS WATCHES/WARNINGS/ADVISORIES

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