


Area Forecast Discussion
Issued by NWS Cheyenne, WY
Issued by NWS Cheyenne, WY
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955 FXUS65 KCYS 160538 AFDCYS Area Forecast Discussion National Weather Service Cheyenne WY 1138 PM MDT Wed Oct 15 2025 .KEY MESSAGES... - A storm system will move through the area today and Thursday, first bringing showers and thunderstorms, followed by mountain snow and strong winds across the wind prone areas of southeast Wyoming. - A few of the thunderstorms this afternoon may become strong to marginally severe, of which they may produce hail and gusty winds along with heavy rainfall. - Clipper system on Saturday brings another round of strong winds and some regional precipitation. && .MESOSCALE... Issued at 227 PM MDT Wed Oct 15 2025 Afternoon GOES satellite imagery reveals a thick blanket of persistent stratus cloud cover over much of east-central Wyoming east of the Laramie Range, as well as the northern and central Nebraska Panhandle. This stratus cloud cover is a visible sign of robust CIN/capping which remains in place over this region. Farther south across Laramie County Wyoming as well as the Kimball to Sidney corridor in the southwest NE panhandle...surface heating and mixing has eroded the morning fog/cloud layer with around 1000 J/kg of SBCAPE present per RAP mesoanalysis fields. To the west of the Laramie range, dewpoint depressions are much higher with some high- based convective cloud cover developing over the Sierra Madre and Snowy ranges. As we move through the later afternoon hours, a deep trough will dig through the Great Basin and Four Corners region. Ahead of this system...favorable dynamics including divergence aloft, a potent mid- level jet streak with 500mb winds in the 50-70kt range, and rapidly cooling mid-level temperatures leading to increasing lapse rates will all combine to place a rather favorable parameter space for strong thunderstorms over southeast Wyoming and western Nebraska. The limiting factor in the thunderstorm forecast today will continue to be instability - or rather a lack thereof. While clouds have cleared along the I-80 corridor east of the Laramie range and surface dewpoints are in the mid to even upper-50s, air temperatures still need about 5-10 degrees of warming to support robust convective initiation. Given the large amount of ML CIN still in place, it is likely that we will have to rely on convective initiation in the mountains to the west, as well as thunderstorms initiating along a developing Denver Cyclone boundary in northeast Colorado. CAM guidance and HREF ensemble members have been more consistent in CI this afternoon and evening in these locations, with storms moving north out of Colorado into southern Wyoming and southwest Nebraska in the 23-01z timeframe. While instability profiles leave much to be desired, the kinematic profile does support multicell to supercell thunderstorm mode with any convection that can maintain itself in the Cheyenne CWA east of the Laramie Range this evening. Long, curving hodographs are present by 0z as the southeasterly low-level jet intensifies underneath strong southwesterly flow aloft. Effective bulk shear over 60 knots and 0-3km SRH in the 150-300 range as seen on both the NAM Nest and recent HRRR runs also support rotating updrafts with threats for hail over 1" in diameter and gusty outflow winds. If surface temperatures were a few degrees warmer, a tornado threat would also be present. Ultimately however, the most likely scenario this afternoon and evening will be for surface-based thunderstorms to quickly become elevated and lose their punch north of the I-80 corridor given capping remaining in place. As stronger forcing moves in aloft after 0z, another round of stronger showers and thunderstorms will likely form over the Laramie range and move through east-central Wyoming. These storms, likely elevated on top of the stable boundary layer, could also bring a wind and hail threat from Wheatland through Torrington and Chadron through around 6z tonight. && .SHORT TERM /THROUGH THURSDAY NIGHT/... Issued at 406 PM MDT Wed Oct 15 2025 Active weather expected through Thursday as a a surface low and attendant frontal boundaries make their way through our region while aloft a deep low lifts up across central Wyoming bringing a strong jet across our region through early Friday. As discussed in the mesoscale section, this will promote the potential for some stronger to severe thunderstorms lifting from our south to north, but the environment is struggling across our more northern zones thanks to the stubborn low stratus deck in this region along and head of the slow lifting warm front. For more information through this evening, see the mesoscale section. As thunderstorms continue into the evening we may see a lingering risk for some stronger activity before waning and becoming more general shower and thunderstorm activity that will continue into Thursday as the cold front associated with this system passes across our region by the morning hours. Post- frontal precipitation may continue into Thursday but should be general shower and thunderstorm activity in nature, alongside some mountain snow for the Sierra-Madre and Snowy ranges. Overall accumulations look to remain light to moderate near the peaks, but should remain low enough to preclude a need for winter products for these zones. Finally, the aforementioned jet and tightened surface pressure gradient should enhance our winds, with stronger gusts starting Thursday afternoon and continuing into Friday afternoon. Currently a high wind watch is out for later Thursday through early Friday afternoon, but this could be extended to start as early as the beginning of the afternoon tomorrow. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... Issued at 406 PM MDT Wed Oct 15 2025 As the trough that brought about our short term weather departs, a secondary clipper trough from our northwest will move across the region Friday into Saturday. While moisture may not be as abundant as it currently is, a few showers and mountain snow showers may be possible. This clipper is bringing in some cooler air, and could even bring snow levels lower than expected with a quick glancing hit of some lower elevation snow, but it would be brief and not expected to accumulate of course. Meanwhile the jet associated with this feature could once again fuel another round of strong winds on Saturday, bringing high wind gusts to our wind prone locations. Sunday a transient ridge will help to clear us out and briefly warm us back into the 60`s to low 70`s, but a deep Pacific trough will bring another round of rain and breezy winds Monday into Tuesday of next week. && .AVIATION /06Z TAFS THROUGH 06Z FRIDAY/... Issued at 1138 PM MDT Wed Oct 15 2025 A few lingering showers continue overnight with the chance for a few rumbles of thunder, mainly out by KRWL. Low stratus will likely continue to push south throughout the night, affecting terminals in the Nebraska panhandle with low CIGs. Low CIGs will lead to MVFR and/or IFR conditions. Fog and dense fog will also be possible which will limit visibility. Fog and low stratus will lift throughout the morning, improving conditions across the area. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...High Wind Watch from late Thursday night through Friday afternoon for WYZ106-107-110-116-117. NE...None. && $$ MESOSCALE...MAC SHORT TERM...CG LONG TERM...CG AVIATION...SF