776 FXUS65 KCYS 101759 AFDCYSArea Forecast Discussion National Weather Service Cheyenne WY 1159 AM MDT Wed Sep 10 2025
.KEY MESSAGES...
- Daily chances for afternoon showers and thunderstorms continue through Thursday with gusty winds, downpours, and isolated hail possible.
- A cold front will impact the area later this week bringing cooler temperatures and chances for showers on Friday and Saturday.
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.SHORT TERM /THROUGH THURSDAY/... Issued at 349 AM MDT Wed Sep 10 2025
With an upper-level ridge moving over the CWA today, expect a mild fall day across the area. Southwest flow aloft will usher in warmer 700 mb temperatures around +14C, leading to high temperatures roughly 5 degrees above average for this time of year. Highs across the area will mainly be in the 80s with perhaps even a 90 degree temperatures or two for parts of the Nebraska panhandle. Unfortunately, the ridge will not be enough to keep precipitation chances at bay. A weak shortwave moving through the ridge this afternoon will provide lift for showers and thunderstorms to develop. Hi-Res guidance has storms developing by mid-afternoon in southeast Wyoming and pushing eastward into Nebraska by the evening hours. Coverage of storms will likely be less than Tuesday, so some locations may see some rain while others may not. Cannot rule out severe storms with GFS model soundings showing pockets of MUCAPE up to 2000 J/kg in the panhandle. Stronger storms could contain severe hail as well as severe wind gusts with DCAPE values over 1000 J/kg. Storms will move out during the evening hours, however, a few showers will linger into the overnight hours as the disturbance moves out of the area.
On Thursday, the upper-level ridge will be east of the CWA, allowing a deep trough to gradually move into the area. 700 mb temperatures will be roughly the same as today, resulting in similar high temperatures on Thursday. With the approaching trough, vorticity maxes will move into the CWA, sparking more storms. Models show greater coverage of precipitation with widespread scattered showers and storms expected for most of the CWA. With MUCAPE values up to 1300 J/kg in the panhandle on Thursday, cannot rule out a marginally severe storm or two. DCAPE values are also above 1000 J/kg so both hail and gusty winds could be possible in storms.
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.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... Issued at 330 PM MDT Tue Sep 9 2025
Long term should remain active initially as a deep trough and low pressure system moves across the region, displacing a high pressure ridge off to our east and cooling us back off, but as this trough weakens over the weekend we should see precipitation chances wane and temperatures moderate themselves to near normal to end the period.
Thursday should be the last day our region remains under the influence of the ridge as it begins to ride eastwards in response to an approaching Pacific trough. This trough then moves into the region Thursday into Friday, bringing an increase in precipitation chances and highs dropping into the 70`s with even some upper 60`s showing up by Saturday. Meanwhile PWAT values will max out around 125-150% of normal, allowing for rainfall across the entirety of the CWA on Friday. While precipitation chances do continue on Saturday, they should be waning as the trough will broaden and less forcing makes its way across our area. Then moving into Sunday and the beginning of next week, a transient ridge will move across as the trough breaks down, but another weaker low will be on the heels of this system just beyond the short term. This overall pattern brings cooler temperatures with the coolest conditions expected on Saturday, with a slight warming trend for Sunday and Monday albeit only a few degrees at best. Meanwhile the precipitation chances start off strong, but should taper off for Sunday into Monday prior to the next system moving in. Ensemble model clusters are in fair agreement, but do show some discrepancies in both the placement and strength of the aforementioned systems, leading to a moderate (60%) confidence in the overall forecast.
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.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/... Issued at 1157 AM MDT Wed Sep 10 2025
VFR conditions expected over the next 24 hours, outside of any thunderstorms that move directly over sites which could bring brief MVFR or lower conditions. Storms already appearing this afternoon, and will continue through the late evening hours before dissipating. All sites have a possibility of a passing storm, though probabilities are too low for KRWL/KSNY to include at this time. Storms may also produce gusty and variable winds. Cloud decks generally mid level, around 10k feet.
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.CYS WATCHES/WARNINGS/ADVISORIES... WY...None. NE...None.
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SHORT TERM...SF LONG TERM...CG AVIATION...CG
NWS CYS Office Area Forecast Discussion