textproduct: Cheyenne

KEY MESSAGES

- Numerous to widespread showers and thunderstorms are expected to begin mid afternoon with multiple rounds possible through Thursday evening.

- Very large hail (up to 4 inches in diameter), strong damaging winds, and a few tornadoes are possible Wednesday afternoon and evening, though the threat is conditional upon storms breaking through a robust capping inversion.

- A Flash Flood Watch has been issued for the South Fork burn scar area due to the potential for multiple rounds of thunderstorms with heavy rainfall in the vicinity.

- Strong winds and heavy rainfall are the primary concerns with Thursday's thunderstorm activity, though large hail is still possible

- Warming temperatures, falling humidity, and increasing winds will increase fire weather concerns this weekend into early next week.

SHORT TERM /THROUGH THURSDAY NIGHT/

Issued at 230 PM MDT Wed Jun 24 2026

We have another conditional threat for severe thunderstorms today across the area. A moisture laden, unstable atmosphere is present with ample vertical wind shear and strong forcing for ascent as a shortwave trough approaches the area. However, as yesterday, we have a stubbornly strong cap in place over most of the High Plains. The low cloud deck has been very slow to break up this morning especially across Laramie county and the southern Nebraska panhandle. Mesoanalysis indicates that MLCIN is still fairly potent over most of the area, though instability is growing over top. MLCAPE is already 1000 to 1500 J/kg, and expected to increase up to about 1500 to 2000 J/kg later this afternoon. Vertical wind shear is quite substantial. 50 to 60+ knots of deep layer is certainly sufficient to support strong to severe thunderstorms. That being said, all of this depends on a storm managing to break through the robust capping inversion. This failed to occur yesterday, but synoptic forcing for ascent is a bit stronger today thanks to stronger overrunning lift and vorticity advection aloft overtop the stalled frontal boundary. So, overall, we have a fairly conditional but still substantial severe threat today. If forcing is enough to get a storm through the cap, it will have the potential to become quite severe with very large hail, frequent lightning, heavy rainfall, strong winds, and a few tornadoes possible. Locally, this looks most likely to happen in Converse, Platte, and Niobrara counties here in the next few hours.

In addition to the typical severe threats, the very high moisture content approaching climatological maximums combined with the potential for multiple rounds of storms will support the potential for localized flash flooding concerns. Confidence is not high enough in widespread flash flooding concerns to issue an area wide Flash Flood Watch. However, it will only take one storm moving directly over the South Fork burn scar to cause significant problems there due to the heightened sensitivity in that area. Thus, a Burn Scar Flash Flood Watch was issued for the area beginning this afternoon and continuing through Thursday evening. There is about a 70% chance for thunderstorms occurring over the burn scar, and perhaps a 50% chance for this potential storm to be producing rainfall rates sufficiently high to lead to debris flow.

Strong isentropic ascent continues through the overnight hours with 500 to 1500 J/kg elevated MUCAPE continuing. As a result, most of the area maintains PoPs through the night and into Thursday morning. The threat for extremely large hail will decrease after about midnight, but an isolated embedded storm may still produce strong winds and/or severe hail. Continued upslope flow in the lower levels overnight will support the development of another round of morning fog and low clouds.

Thursday will continue the stormy weather pattern. While temperatures will be cooler across the area and low clouds will still be present in the morning, capping looks like less of a concern on Thursday. This will be due to the decrease in temperatures around 700-mb anticipated over the next 24 hours, which will decrease the magnitude of the warm air inversion aloft. On the flip side, lapse rates and instability look lower weaker tomorrow compared to today. After a morning to early afternoon round of showers with embedded thunderstorms, we will need to watch for another late afternoon and evening round of stronger thunderstorms organized along surface frontal boundary trailing south of a shortwave trough passing to our north. It continues to appear likely that this will help storms organize into a linear feature riding on the leading edge of a strong surface cold pool. The shallower lapse rates and linear forcing suggest a decreased hail risk on Thursday, but perhaps an increased risk for strong thunderstorm winds. High resolution models struggle to handle this mesoscale cold front upon reaching the surface high entrenched over the High Plains. Falling surface pressure over western Wyoming, eastern Idaho, and northern Utah will increase southerly flow Thursday night, leading to good moisture return and another round of low clouds or fog into Friday morning.

LONG TERM /FRIDAY THROUGH WEDNESDAY/

Issued at 230 PM MDT Wed Jun 24 2026

Friday...Low amplitude ridging develops over our forecast area, with some drier air noted advecting in. However, still expect isolated to widely scattered afternoon and evening thunderstorms to form along a low level convergence axis along the I-25 corridor. A few strong and possibly severe storms may occur.

Saturday...The flow aloft turns southwest and increases in speed, with considerably drier air moving across our counties, producing a dry day with a warming trend as 700 mb temperatures spike near 16 Celsius.

Sunday through Wednesday...A broad trough aloft develops across the northern and central Rockies, with dry southwest flow aloft, leading to only isolated to widely scattered thunderstorms at most in the afternoons and evenings. A progressive shortwave trough aloft is progged to move to the western Dakotas on Monday, with its associated cold front bringing a cooler airmass behind the likely moisture starved cold front. The dry southwest flow aloft continues for Tuesday and Wednesday with a slow warming trend.

AVIATION /00Z TAFS THROUGH 00Z FRIDAY/

Issued at 559 PM MDT Wed Jun 24 2026

Complex scenario over the next 24 hours as severe thunderstorms are ongoing at this time, which are producing large hail, damaging winds, and heavy rainfall. This will result in sporadic LIFR and IFR conditions into tomorrow as we expect additional showers and thunderstorms to persist overnight into tomorrow morning. CIGs will lower to below 1 kft and visibilities will decrease to below one statue mile in the stronger thunderstorms. Outside of showers and thunderstorms, expect MVFR CIGs with the possibility of fog during the overnight and early morning hours, primarily for the Nebraska terminals where the greatest low-level moisture exists. Confidence is high enough to include BR in the TAFs.

CYS WATCHES/WARNINGS/ADVISORIES

WY...None. NE...Flash Flood Watch through Thursday evening for NEZ002-095.