textproduct: Cheyenne

KEY MESSAGES

- There is a Slight Risk (Level 2 of 5) from Laramie county to Kimball county. A Marginal Risk of Excessive Rainfall is also in place for today.

- There is a Marginal Risk (Level 1 of 5) for severe weather for portions of southeast Wyoming and western Nebraska on Thursday. Large hail and damaging wind are the primary hazards.

- Friday will act as a transition day between active weather to more organized active weather Saturday onwards.

- Daily shower and thunderstorm chances expected Saturday through at least Thursday, with the potential for strong thunderstorms Sunday afternoon.

SHORT TERM /THROUGH THURSDAY NIGHT/

Issued at 200 PM MDT Wed Aug 26 2026

The main shows looks to start around 5pm according to model soundings. Right now we have showers developing off the mountains as we reach convective temperature. Model soundings had the convective temp around 75 degrees and its now 78 degrees here at the office and showers are cropping up along the mountains. The RAP had peak MUCAPE values at around 2,000 to 2,500 joules by 21-23z in the southern Panhandle and Laramie county. For our northern counties the soundings estimated between 600 to 1500 joules with the higher energy values being over the Panhandle where there is more moisture. Bulk shear was around 40-50kts looking at the GFS and soundings pinned around 20-25kts for effective shear. The environment looks a lot better today for producing severe thunderstorms then it did yesterday. However, the Lapse rates are not to spectacular ranging between 7.0 to 7.5C so the storms may take a hot second to develop their own suitable environment to really intensify into a self- sustaining storm. SPC has placed a slight risk (level 2 out of 5) over Laramie county and extended it into Kimball county where the best environmental conditions lie to produce supercells.

Another active day is anticipated for Thursday as the upper-level ridge remains in place across much of the Intermountain West. The ridge is expected to amplify Thursday afternoon with northwesterly flow aloft continuing. As the ridge amplifies around 21Z Thursday, a weak jet develops from eastern Montana southeastward into western and central South Dakota. This positioning will broadly place the region in the right entrance region of the jet, but it will be much weaker than what is expected today. The ridge will be pushed back to the southeast throughout the overnight hours as an upper-level trough starts to push into the Pacific Northwest by 06Z Friday. Looking down at 500mb, a similar pattern to Wednesday will setup with the high over the Four Corners region funneling moisture into the region and allowing multiple lobes of 500mb vorticity to advect around the high into the CWA. 700mb flow will be quite weak once again Thursday afternoon with broad ridging expected to remain overhead. One big difference between today and Thursday will be the significantly stronger 700mb WAA on Thursday. A stout surface low pressure system is projected to develop and move across northeast Wyoming, favoring increased southerly to southeasterly flow across the region and stronger surface winds due to the increased pressure gradient. This low will move eastward, dragging a weak cold front across the region between 03 and 09Z Thursday night into Friday morning. Forecast soundings from the HRRR and RAP suggest much more instability present Thursday afternoon in western Nebraska, with MLCAPE around 2000 to 2500 J/kg, though 2500 J/kg may be a touch high. SBCAPE skyrockets to around 2000 J/kg and DCAPE increases to 1300 to 1500 J/kg Thursday afternoon. An isolated storm or two could become strong to severe Thursday afternoon with the Storm Prediction Center placing western Nebraska in a Marginal Risk (Level 1 of 5) for severe weather with damaging winds and large hail as the primary hazards. Tornadoes, once again, do not look likely. The Marginal Risk for excessive rainfall is pushed much more to the southeast for Thursday, only including Kimball to Sidney and points southeastward. Flooding does not look overly likely Thursday, but heavy rain may still be possible with Precipitable Water values once again around an inch in the Panhandle.

LONG TERM /FRIDAY THROUGH WEDNESDAY/

Issued at 200 PM MDT Wed Aug 26 2026

Friday starts off this long term period with the upper level ridge staying put and the trough moving to the east, tilting toward the northeast. A westerly flow comes to the 700mb height as the ridge begins to weaken and push out of the area. 700mb winds increase with the height gradient tightening. Surface winds are expected to be stronger and gusty. Carbon county can expect to see the strongest and gustiest winds. Temperatures at 700mb increase between 15 to 19C in the afternoon on Friday. Afternoon minimum humidity values are expected to be between 15 to 20 percent for much of the CWA. This along with gusty winds brings elevated fire weather conditions.

An upper level trough moves through the PNW through this long term period. Upper level flow increases as the weekend progresses, supporting chances for showers and storms on Saturday and Sunday. Sunday looks to be an active day with a trough starting to negatively tilt over central Montana. A strong jet develops stretching from eastern Montana through Western Nebraska. Sunday afternoon will have strong forcing due to much of the region being in the right entrance region of the upper level jet. Some models show good WAA at 700mb. This coupled with the strong upper level jet primes the atmosphere for strong storms on Sunday. More to come as we get closer to Sunday. Monday and Tuesday bring more chances for storms and showers. Temperatures stay warm through Saturday then cool off starting on Sunday, bringing more seasonable temperatures as we head into September.

AVIATION /00Z TAFS THROUGH 00Z FRIDAY/

Issued at 520 PM MDT Wed Aug 26 2026

Showers and thunderstorms are pushing through and will affect all terminals at varying times and to different degrees, except KRWL and KLAR where they have the best shot at escaping any impacts. This activity may drop CIGs and VIS for a short period of time if the storm passes over a terminal. Look for AMDs if this is the case over the next several hours. Also, anticipate gusty and erratic winds in any storm activity. After all these storms push through, a return of VFR conditions are expected overnight across all the sites with winds generally 10 knots or less.

CYS WATCHES/WARNINGS/ADVISORIES

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