textproduct: Cheyenne

KEY MESSAGES

- Hot and dry conditions will persist through the end of the week with Friday likely being the hottest day out of the next several.

- Elevated to near-critical fire concerns expected Thursday and Friday, though Red Flag criteria is currently not expected to be met.

- Daily shower and storm chances return Monday through the end of the week with slightly above average temperature expected until Thursday.

SHORT TERM /THROUGH FRIDAY NIGHT/

Issued at 212 AM MDT Thu Aug 20 2026

Upper-level ridging will persist today as the ridge builds throughout the day. 500mb flow remains benign, but a few vorticity maxima will eject across the region this afternoon. Clear skies this morning look to become partly cloudy as these vorticity maxima general clouds across the region. Westerly to northwesterly flow persists at 700mb this afternoon with GFS Omega fields suggesting weak downward motion along the Laramie Range. This downsloping will continue to dry out the lower levels today making precipitation chances near zero for the afternoon. 700mb temperatures will warm into the 14 to 19C range this afternoon, leading to surface temperatures soaring into the mid-80s to mid-90s across the entire CWA. Thankfully, surface gradients are progged to remain minimal, decreasing the potential for Red Flag criteria winds across the region. Afternoon minimum humidity values will drop into the 12 to 22 percent range, but relatively calm winds and several days of moisture will prevent critical fire danger this afternoon.

Similar to Thursday, upper-level ridging strengthens on Friday as the upper-level ridge drifts eastward and remaining directly overhead. The ridge axis will be just off to the west of the CWA, but very warm temperatures are still anticipated. 500mb flow remains benign once more with multiple vorticity maxima ejecting across the CWA, once more increasing cloud cover into the afternoon hours. Weak, westerly 700mb flow persists throughout much of the day Friday, with omega fields once again suggesting modest downsloping throughout the afternoon hours. 700mb temperatures will increase to the 15 to 19C range on Friday as the upper-level ridge creeps closer to the region. As a result, surface temperatures will skyrocket into the upper-80s to upper-90s, with a few sites near 100F, Friday afternoon. Afternoon minimum humidity values will once again drop into the 15 to 25 percent range across the region with winds once again remaining reactively light and, therefore, reducing fire concerns for Friday afternoon. There is a small chance for an isolated shower or storm to develop off the Laramie Range, but PoP values remain only at 15 percent for a small portion of the area between Cheyenne and Laramie. A very weak cold front will push into the region Friday evening into the overnight hours and drop 700mb temperatures by a couple degrees and flip the 700mb flow to a more easterly component. Resulting easterly flow at the surface Saturday morning may result in some low clouds or fog, but these will first need to overcome the very dry conditions expected due to continued downsloping Friday afternoon.

LONG TERM /SATURDAY THROUGH WEDNESDAY/

Issued at 212 AM MDT Thu Aug 20 2026

Upper-level ridging continues to dominate the long term weather pattern, with models suggesting the ridge starting to breakdown Monday evening into the overnight hours Tuesday. For Saturday, the ridge will be planted directly overhead with much stronger 500mb vorticity maxima ejecting across the CWA. 500mb flow also suggests that monsoonal moisture will start to return to the area Saturday after being largely cutoff by the developing upper-level ridge. Behind the weak cold front moving through the region Friday afternoon and evening, 700mb temperatures will drop into the 14 to 16C range with 700mb flow flipping more southerly across the region ahead of an incoming 700mb shortwave trough. Weaker easterly flow is expected mid-day Saturday before surface pressure gradients start to increase into the afternoon hours, resulting in increasing easterly winds across the region. Surface temperatures will be cooler than Friday, in the low-80s to low-90s across the region. Easterly surface flow combined with the return of some monsoonal moisture and the forcing provided by the incoming shortwave trough will help initiation showers and storms along the Laramie Range into the evening and overnight hours. Thanks to this returning moisture, precipitable water values will increase to the 97.5th percentile, just over an inch for much of the CWA. Therefore, showers and storms on Saturday may produce heavy rain, which will act to further limit fire weather concerns through the weekend.

A slightly more dynamic setup is expected Sunday as the upper-level ridge continues to push easterly before flattening out by Monday afternoon. Westerly to southwesterly flow aloft is anticipated as the ridge advances eastward with multiple 500mb vorticity maxima pushing through the region. 500mb flow continues to support the return of monsoonal moisture region with westerly flow developing at 500b with a fetch all the way to the Pacific Ocean just off the coast of southern California. NAEFS Mean Precipitable Water continues to suggest PWs in the 97.5th percentile across the region Sunday, which is favorable for heavy rain across the region. The 700mb shortwave trough will continue to push easterly Sunday morning into the evening hours, taking with it the best forcing. A 700mb ridge starts to build off to the south and west after the shortwave pushes out of the region with westerly flow developing across the CWA. Isolated to scattered showers and storms may develop mid-day and continue through the evening hours Sunday, despite ridging remaining aloft and the best forcing well off to the east. Sunday will be warmer than Saturday as 700mb temperatures increase until the advancing ridge, with highs expected to be in the mid-80s to mid- 90s once more.

A brief period of zonal flow aloft develops for Tuesday and most of Wednesday before another ridge begins to build across the western CONUS starting Wednesday and continuing through the end of the week. 700mb flow remains largely calm during the week. Several 500mb vorticity maxima will push across the region as the monsoonal moisture fetch remains open across the region. Daily shower and storm potential is expected Monday through much of the week, with heavy rain possible each day. Temperatures will be warm for most of the week, but not overly hot. Daily high temperatures will be in the low- to upper-80s through Wednesday. As the ridge begins to build back over the region Wednesday and Thursday, temperatures start to increase with high temperatures in the mid-80s to mid-90s expected to return by Thursday.

AVIATION /12Z TAFS THROUGH 12Z FRIDAY/

Issued at 507 AM MDT Thu Aug 20 2026

VFR conditions anticipated to persist throughout the entire 12Z TAF period with clear skies and relatively calm winds this afternoon. High clouds will slowly increase for the evening hours with winds starting to drop back to variable around 6kts. KRWL may see and isolate showers or two today, but confidence is low in timing. Gusty and erratic winds will be possible with any shower that forms.

CYS WATCHES/WARNINGS/ADVISORIES

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