Area Forecast Discussion
Issued by NWS Cheyenne, WY

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453 FXUS65 KCYS 260332 AFDCYS Area Forecast Discussion National Weather Service Cheyenne WY 932 PM MDT Tue Jun 25 2024 .KEY MESSAGES... - Critical fire weather conditions continue this afternoon over the High Plains, generally south of the North Platte River. - Moisture will return to the High Plains on Wednesday and Thursday, leading to the potential for some strong thunderstorms and heavy rainfall in the afternoon and evening. && .SHORT TERM /THROUGH WEDNESDAY NIGHT/... Issued at 300 PM MDT Tue Jun 25 2024 Hot, dry, and breezy afternoon across southeast WY and western NE with GOES WV imagery continuing to show a dry airmass moving overtop of the southwest CONUS ridge. Much of the I-80 corridor has reached Red Flag criteria with gusty northwest winds around 25-35 mph. A frontal boundary positioned north of the North Platte River valley has held on to higher dew points across the northern NE panhandle, limiting fire weather potential despite hot temperatures in the upper 90s. At this hour, Scottsbluff has reached 100F degrees which will likely be the warm spot for the day. Isolated high-based showers and thunderstorms have been moving across the CO/WY border this afternoon and will continue to do so into early this evening with weak shortwave energy passing overtop of the ridge. Currently there are a few storms south of the border near Red Feather Lakes with additional storms developing out of the Uintas that will need to be monitored along the CWA border for gusty outflow winds. Headed into tonight, the frontal boundary will begin to slide south turning winds more easterly with the return of low-level moisture up against the Laramie Range. Turning ahead to Wednesday, expect the return for showers and thunderstorms across southeast WY and western NE with a shortwave passing over the ridge centered over the southern Rockies ahead of an upper level trough approaching the PacNW. CAMs suggest CI by the early afternoon over the higher terrain, increasing in coverage through the afternoon with better lift associated with the shortwave a DPVA approaching from the west. Additionally, storms will intensify upon crossing the moisture boundary where 1000-1400 J/kg of MLCAPE sits across Platte/Goshen Co. Upper level flow will be better across east- central WY with speed shear, but regardless 0-6 km shear values will be 45-50 kt leading to strong to severe thunderstorms with hail and strong winds late in the afternoon into early Wednesday evening. Favorable lift will likely lead to cold pool organization and upscale growth as storms move across the NE panhandle. PW values are also forecast to reach 1.25" leading to efficient rain producing storms and the potential for localized flooding. The limiting factor there will be the quick progression of the eventual system as the shortwave passes through. && .LONG TERM /THURSDAY THROUGH TUESDAY/... Issued at 300 PM MDT Tue Jun 25 2024 The medium range to extended forecast includes near to above average temperatures and an active weather pattern. Thursday will be the most active for the medium range portion of the forecast, with daily chances for afternoon thunderstorms for parts of our cwa as we look to the end of June and the first part of July. A weak cool front will pass through the area Thursday before we gradually begin to warm up through the weekend. Thursday will be another hot day as we are under the influence of a decaying upper level ridge. During peak diurnal heating, we will see the atmosphere become unstable. PWATs will surge as the GoM moisture advects northward by late Thursday. Lapse rates will be sufficient for thunderstorm initiation. Effective bulk wind shear will not arrive until closer to Thursday evening, however. At this time of inspection, would expect convection to develop thanks in part of the elevated mixed layer becoming involved with the higher terrain across southeast WY. Thunderstorms will potentially cause heavy downpours for areas that see a strong thunderstorm or two. Highest confidence for this to occur would be across southeast WY before any type of discrete thunderstorm begins to become more of a line segment in the NE Panhandle where the best moisture, lapse rates, instability and forcing from the weak cold front is realized most. Daytime highs in the 80s and 90s are anticipated for locations east of the Laramie Range, and 70s for regions west of the Laramie Range. Friday will have cooler temperatures as we are on the periphery of a passing shortwave disturbance to our north. Daytime highs will be approximately 5-10 degrees cooler for Friday compared to Thursday. The decaying upper level ridge across the Central Rockies will allow for weak instability to become present by Friday evening. A few showers and isolated rumbles of thunder along the I-80 corridor look to be favored for Friday evening before dusk. Monsoon moisture off the Mexican plateau will advect north on Saturday as a broad, surface high over the southeast U.S. brings additional impulses of moisture to our area. Thunderstorms will be possible for portions of our cwa, but coverage will be limited. Daytime highs will be similar to that of Friday on Saturday. Sunday will be the next best opportunity for a couple of strong thunderstorms. Lee side troughing east of the Rockies will combine with moisture and daytime heating for thunderstorm activity to increase in coverage by the afternoon. Coverage appears to be larger for CO, but wouldn`t be surprised for that convection to slowly propagate north into portions of our cwa. Warmer temperatures make a return as well by early next week. Daytime highs in the 80s and 90s east of the Laramie Range will become prevalent. Our forecast area will become wedged between broad troughing to our north, and the weak upper level ridging to our south. This quasi-zonal flow aloft will likely help instigate another round of thunderstorms by early next week. Stay tuned for further updates on the extended forecast as we may have the potential for isolated severe weather once again. && .AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
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Issued at 927 PM MDT Tue Jun 25 2024 West northwest flow aloft will continue, with increasing low and mid level moisture and a weather disturbance helping to increase cloud cover and the coverage of showers and thunderstorms Wednesday afternoon and evening. Clear skies will prevail until 15Z, except for occasional fog reducing visibilities to 4 miles and ceilings to 1500 feet from 09Z to 13Z at Chadron, Alliance and Scottsbluff. After 15Z, scattered to broken clouds from 5000 to 10000 feet will occur, with thunderstorms in the vicinity at all terminals except Rawlins after 00Z. Winds will gust to 25 knots at the Wyoming terminals after 15Z Wednesday, and to 30 knots at the Nebraska terminals after 15Z to 21Z Wednesday.
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&& .FIRE WEATHER... Issued at 300 PM MDT Tue Jun 25 2024 Elevated to critical fire weather conditions continue this afternoon along and south of the North Platte River valley with gusty west to northwest winds colocated with RHs in the low teens. Fuels are currently listed as non-critical west of the Laramie Range, but have recently switched over farther east and extending into the southern Nebraska panhandle. Expecting good recoveries east of the Laramie Range as overnight easterlies behind the frontal passage will bring back low-level moisture. Temperatures will be cooler, but still above average for the remainder of the week into this weekend decreasing fire weather concerns. Afternoon showers and thunderstorms likely Wednesday and Thursday afternoon with the chance for wetting rainfall, especially across the Nebraska panhandle. && .CYS WATCHES/WARNINGS/ADVISORIES...
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WY...None. NE...None.
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&& $$ SHORT TERM...MB LONG TERM...BW AVIATION...RUBIN FIRE WEATHER...MB