198 FXUS65 KCYS 042329 AFDCYS Area Forecast Discussion National Weather Service Cheyenne WY 529 PM MDT Fri Jul 4 2025 .KEY MESSAGES... - Afternoon and evening showers and storms may impact Independence Day festivities. Gusty winds and lightning are the primary threats. - Scattered PM thunderstorms with the potential to become strong to severe will continue through the weekend and into early next week. - Hot temperatures are possible by mid to late next week. && .SHORT TERM /THROUGH SATURDAY NIGHT/... Issued at 300 PM MDT Fri Jul 4 2025 Stormy weather continues this Independence Day across the area. Current GOES water vapor imagery shows the first shortwave responsible for the nocturnal and morning shower and thunderstorm activity earlier today now moving east across central Nebraska. however, another upper level low currently located over the Pacific Northwest has a vorticity axis stretching to its southeast, the axis of which is now moving across western Wyoming. This is tapping into the abundant moisture lingering over the area behind yesterday`s surge of moisture out of the monsoon region. Dewpoints west of the Laramie range remain in the mid to upper 40s, while the Nebraska panhandle is pushing from the mid 50s to even low 60s near Alliance. Decent southwest flow is apparent aloft, but westerly surface winds are limiting the shear on the Wyoming side. The latest mesoanalysis depicts two areas of slightly greater instability over about 1000 J/kg (surface based): the first over Carbon into Converse County where mid level lapse rates are steep, and the second over the Nebraska panhandle where low-level moisture is highest. All together, this is painting a fairly muddy picture for this afternoon and evening`s convective activity. Widely scattered showers and thunderstorms have already kicked off and will continue to move east through the evening with a few successive rounds possible. With fairly saturated mid-levels and only modest instability, the large hail threat today isn`t very high, but storms will have the potential to produce strong, gusty winds and lightning, which can certainly be a problem with many folks outdoors today. Additionally, we will need to watch for the development of a meso-high. This is already apparent over northwest Wyoming on the latest mesoanalysis. Hi-res model guidance shows this strengthening and moving east through the evening. This may be able to organize more linear convection along its leading edge, and provide a focus for stronger winds with thunderstorm activity. If this materializes, it should creep into Carbon/Converse counties around 5-6PM, reaching the US- 385 corridor by 10-11PM. Confidence is fairly low in whether a system will organize along this, but it will warrant close watching as that would be the main piece to interfere with evening festivities. Most activity should be done by midnight, aside from perhaps some lingering showers with embedded thunder over Carbon county until about 3AM or so. Skies will trend towards clear Saturday morning as the axis of a modest upper level ridge parks overhead. The PNW upper level low will shift eastward to the northern Rockies by tomorrow, and another band of elongated vorticity on its southern flank will move off of the mountains during the afternoon hours. A surface low developing over central Wyoming will pull drier air back into Carbon county and amplify the dryline along the Laramie range which should provide a focus for initiation of afternoon thunderstorms. Forecast soundings show steeper lapse rates with moisture remaining plentiful on Saturday, leading to more instability than what we see today. Vertical wind shear looks marginal but sufficient for a few strong to severe thunderstorms to develop. && .LONG TERM /SUNDAY THROUGH FRIDAY/... Issued at 300 PM MDT Fri Jul 4 2025 An active start to the long term is expected as a few shortwaves move north of the CWA. The first shortwave will graze the northern part of the forecast area on Sunday. This shortwave will provide needed lift and some of the moisture to produce thunderstorms across the area. Model soundings show a decent environment for strong to severe storms to develop in the Nebraska panhandle. Soundings show about 1800 J/kg of MUCAPE with around 35 kts of effective shear. DCAPE values are also high with values around 1500 J/kg. This will lead to primarily a wind and hail threat in storms that develop. Severe chances look even more favorable on Monday. Model soundings in the Nebraska panhandle show up to 2500 J/kg of MUCAPE with 35 to 40 kts of shear. This will support a large hail threat. DCAPE values are similar to Sunday, so damaging winds will still be a possibility. MLCAPE is also rather high, at about 1600 J/kg with SFC- 3km SRH at about 100 m^2/s^2. This could support an isolated tornado threat Monday afternoon as a secondary shortwave passes north of the CWA. The 500 mb high over the Four Corners region will strengthen mid- week, also strengthening the ridge over the Rockies. As a result, a fast warm up is expected. High temperatures will make a return to the 90s for most locations by Tuesday, with even hotter temperatures expected Wednesday as 700 mb temperatures climb to +20C! Precipitation chances during this time will also be minimal as desert air and subsidence under the ridge keep conditions dry. Slightly cooler temperatures and better precipitation chances return to the area on Thursday as a shortwave moves across the area. && .AVIATION /00Z TAFS THROUGH 00Z SUNDAY/... Issued at 522 PM MDT Fri Jul 4 2025 West flow aloft will continue. Wyoming TAFS...Scattered to broken clouds from 9000 to 15000 feet will prevail. Thunderstorms will be in the vicinity of the terminals until 02Z, with occasional thunderstorms at Rawlins and Laramie until 02Z, producing wind gusts to 45 knots. Outside of thunderstorms, winds will gust to 25 knots until 03Z, and to 24 knots at Rawlins after 15Z Saturday. Nebraska TAFS...Scattered to broken clouds from 7000 to 15000 feet will prevail. Thunderstorms will be in the vicinity until 02Z. Outside of thunderstorms, winds will gust to 23 knots at Sidney until 02Z. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...None. NE...None. && $$ SHORT TERM...MN LONG TERM...SF AVIATION...RUBIN