


Area Forecast Discussion
Issued by NWS Cheyenne, WY
Issued by NWS Cheyenne, WY
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909 FXUS65 KCYS 162352 AFDCYS Area Forecast Discussion National Weather Service Cheyenne WY Issued by National Weather Service Rapid City SD 552 PM MDT Wed Jul 16 2025 .KEY MESSAGES... - Scattered strong to severe thunderstorms are expected Wednesday afternoon and evening in southeast Wyoming and southwest Nebraska. Large hail is the primary threat, but all severe weather hazards are possible. - Warmer temperatures and isolated to scattered late day showers and thunderstorms will occur for Thursday through early next week. && .SHORT TERM /THROUGH THURSDAY NIGHT/... Issued at 1248 PM MDT Wed Jul 16 2025 Current satellite imagery shows low stratus covering areas east of the Laramie Range. Satellite also shows some gradual clearing within the stratus, which will likely lead to destabilization later this afternoon. Low stratus from weak southerly and easterly flow will provide ample moisture for storms. A sharp dryline along the Laramie Range, as well as a weak disturbance aloft will provide the needed lift for storms to initiate later today. Hi-Res guidance still shows an active afternoon and evening, mainly across southeast Wyoming where storms have the greatest potential to be severe. GFS soundings show a strongly capped Nebraska panhandle through the afternoon, which will help limit both storm development and strong storms. By mid- afternoon, the capping inversion along the Interstate 25 corridor will be eroded. This is likely around the time when stronger storms will start to develop. Model soundings along the Interstate 25 corridor do show an environment favorable for severe weather. MUCAPE values are around 1400 J/kg with effective shear values around 40 kts. This lends itself to a severe hail threat, as well as the more discrete cells models are showing. DCAPE values are around 1000 J/kg west of the Laramie Range where it is drier and sunnier. These areas could see some severe wind gusts with storms. Cannot rule out an isolated tornado this afternoon with elevated SFC-3km SRH and effective shear values. Heavy rain is also expected in storms with PWATs above the 90th percentile for climatology. Luckily, storms appear to be quick moving this afternoon, however, multiple rounds of storms as suggested by some models could lead to localized flash flooding. Strongest storms should end by about 8 PM with some lingering showers and storms possible through midnight. Quieter weather is expected for Thursday. Southerly flow and residual moisture from storms will likely lead to another round of low stratus during the morning hours. However, zonal flow aloft will help dry out the mid-levels and clear clouds out by the afternoon. Storms will still be possible during the afternoon hours from a weak disturbance aloft, however, coverage and intensity of storms will be much lower than today. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... Issued at 344 AM MDT Wed Jul 16 2025 A zonal flow pattern will take over aloft on Thursday and dominate much of the northern half of the CONUS into the weekend. Drier westerly flow aloft will reduce the risk for storms on Thursday, but isolated thunderstorms will still be possible, mainly along the I-80 corridor. Monsoon moisture will be pulled into the flow on Friday, causing perceptible water and mid-level moisture in general to recover. While mid to upper level moisture should improve for Friday, the dryline is expected to be positioned further east, resulting in fairly steady precipitable water Thursday into Friday. Expect to see some high-based showers and thunderstorms with gusty winds possible on Friday along with warm to hot temperatures. Ensembles indicate that the dryline will move back to the west on Saturday while decent mid to upper level monsoon moisture remains in place. Expect this to then bring the highest chance for more widespread shower and thunderstorm coverage of the long term period. For Sunday through Tuesday or so, expect decent monsoon moisture to remain in place aloft, but we may lose the boundary layer moisture for several days, leading to more isolated PM thunderstorm activity each of those days. Additionally, an upper level trough digging into the northwest will amplify the downstream ridge over the central plains, leading to another warm trend to carry through the middle part of next week. && .AVIATION /00Z TAFS THROUGH 00Z FRIDAY/... Issued at 550 PM MDT Wed Jul 16 2025 Stalled surface cold front and associated weak low is forecast to slowly lift northeast this evening through tonight as a warm front. Numerous showers and thunderstorms expected over southeast Wyoming over the next few hours before conditions improve after 04z. Patchy fog and low clouds expected for all eastern plains terminals later tonight. HAZARDS/WEATHER TRENDS: Thunderstorms with very heavy rainfall, hail, gusts winds up to 50 knots expected over the next two hours until 02z for mainly KLAR and KCYS and possibly KBFF. Storms will push southeast into Colorado around 03z with MVFR conditions with CIGS around 1500 to 2500 feet. Fog and IFR CIGS expected to develop quickly around 06z to 08z for all western Nebraska terminals and KCYS. Lower confidence for KLAR and KRWL, so will leave out of the TAF for now. Conditions are not expected to improve to VFR until 18z. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...None. NE...None. && $$ SHORT TERM...SF LONG TERM...SF AVIATION...TJT