textproduct: Cheyenne

KEY MESSAGES

- Cooler temperatures on Saturday alongside some isolated shower or storm chances but remaining weak overall.

- Temperatures warm on Sunday and Monday with increasing precipitation chances, though Monday may see the return of critical fire weather conditions.

- Much cooler on Tuesday with temperatures a few degrees warmer through the end of next week and daily chances of showers and thunderstorms.

SHORT TERM /THROUGH MONDAY/

Issued at 156 PM MDT Sat Sep 12 2026

A few afternoon and evening showers are following the axis of instability along the southern half of the forecast area as a weak shortwave pushes through the area. A few brief showers are possible with some of the stronger storms but nothing severe or heavy rain is expected. These showers are expected to last through the evening with showers possible about as far north as Scottsbluff, NE. Wind gusts are expected to last overnight east of the I-25 corridor as the upper level low pushes into the Intermountain West from Pacific Northwest near Montana. Scattered thunderstorms be possible tomorrow as another shortwave passes through our neck of the woods. Some strong to possibly severe thunderstorms could develop in the late afternoon as a surface low moves northeast through our forecast area. CAPE values look to be between 500 to 1,000 joules with couple potential pockets of 2,000 joules as depicted by the RAP between 3 to 7pm. The synoptic forcing of the surface low should sustain the showers and thunderstorms through the evening. However, in the morning we have a substantial cap to erode away in the morning and afternoon before any strong to severe thunderstorms could develop. It will be a little tough too since the forecasted convective temperature for tomorrow is in the mid 80's and the forecasted high temperature are either at or below the convective temperatures. Because of this setup with the strong morning capping SPC has us in a general thunder risk for Sunday favoring the low level cool temperatures and strong capping limiting any potential severe thunderstorms.

LONG TERM /MONDAY NIGHT THROUGH FRIDAY/

Issued at 156 PM MDT Sat Sep 12 2026

Active weather is expected for much of the upcoming week with multiple upper-level disturbances pushing through the region. Monday features the strongest disturbance expected for the week as a stout upper-level trough digs across Montana with a 100kt jet along the southeastern portion. The jet will move eastward with the upper- level low, placing the CWA within the right entrance region of the upper-level jet for much of the day Monday. Enhanced, dynamically- driven ascent will provide much needed forcing for showers and thunderstorms Monday morning and afternoon. Multiple 500mb vorticity maxima will eject across the area as the upper-level low moves eastward, favoring addition forcing across much of the region. The 700mb low is expected to be displaced to the north across the southern Saskatchewan Province. While this low will be displaced to the north, it looks to be quite strong, with an associated jet around 50 to 60kts over the Northern Plains. For Southeast Wyoming and Western Nebraska, the low will lead to strong, westerly flow across the CWA around 40 to 45kts Monday morning. If you have lived in this area for a while now, you may know where this is heading... The surface low with this system will dive southeastward from the Black Hills towards central Nebraska, with a strong, trailing cold front. This low progression is favorable for strong, west to east surface pressure gradients to develop across western portions of the area and across the Laramie Range. The surface pressure gradient across the Laramie Range peaks around 2 to 3mb Monday morning. GFS Omega field suggest modest to strong downward motion along the Laramie Range and just east. With all these factors considered, Monday morning will likely see very strong winds across much of the region, though a High Wind Warning is currently not anticipated, but this may change as this event moves into the short term. In-house random forest model guidance is giving around a 30 to 40% chance for high winds at Arlington, Rawlins, Bordeaux, Coleman, and northern Carbon County. Therefore, high wind criteria winds cannot be completely ruled out at this time and this setup will need to be monitored closely as Monday morning approaches.

In addition to the potential for strong to near-high wind criteria winds, this system will bring a strong cold front to the region, dropping temperatures from the low-70s to upper-80s on Monday into the upper-60s to mid-70s on Tuesday. Most locations east of the Laramie Range will be around 10 to 12 degrees cooler on Tuesday. Additionally, isolated to scattered showers will be possible Monday with the front moving through, resulting in low-level forcing for ascent. Dewpoints in the 50s and 60s east of the Laramie Range on Monday will favor precipitation development with the front, before dewpoints tank into the 30s and 40s behind the front. With the frontal passage timing, precipitation will be largely confined to the I-80s corridor across the region. The long range models currently suggest that some CAPE may be present across the region Monday morning and afternoon, so an isolated storm or two cannot be ruled out especially across the southern Panhandle.

After the cold front Monday, temperatures will remain quite nice through the remainder of the week, likely staying in the 60s and 70s with a couple of low-80s possible Wednesday. Daily precipitation chances are expected as the upper-level flow remains more dynamic than it has been in the past several weeks.

AVIATION /00Z TAFS THROUGH 00Z MONDAY/

Issued at 545 PM MDT Sat Sep 12 2026

A few showers and embedded thunder may impact the Interstate 80 corridor through 02z. Otherwise, clearing skies are expected tonight with breezy southeast winds at times across the eastern plains.

HAZARDS/WEATHER TRENDS: VFR conditions will prevail over the next 18 to 24 hours with shower and thunderstorm activity weakening this evening. Can't rule out some low clouds developing tonight across the eastern plains due to southeast surface winds, but probabilities are low enough (< 10 percent) to keep out of the TAF.

CYS WATCHES/WARNINGS/ADVISORIES

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