Area Forecast Discussion
Issued by NWS Cheyenne, WY
Issued by NWS Cheyenne, WY
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380 FXUS65 KCYS 301755 AFDCYS Area Forecast Discussion National Weather Service Cheyenne WY 1155 AM MDT Sun Jun 30 2024 .KEY MESSAGES... - A few strong to severe thunderstorms this afternoon and evening. Maybe better chances for severe thunderstorms Monday afternoon and evening. - Cooler week ahead before strong ridge and toasty temperatures return for the weekend. && .SHORT TERM /THROUGH TUESDAY/... Issued at 300 AM MDT Sun Jun 30 2024 Frontal boundary lays along a line from northeast New Mexico...north along the front range to Laramie and eventually north central Wyoming this morning. Southeasterly low level winds have raised dewpoints this morning east of this front. Seeing mid 50 dewpoints in the Panhandle so far this morning with low 50s here at Cheyenne. West of the front...dewpoints in the 40s being reported across Carbon County. Dilemma of the day will be whether severe storms are going to form or not. Looks like the Panhandle stays pretty capped through 00Z today. Towards 00Z...low level capping inversion finally break...with GFS MUCAPE increasing to around 1500 J/KG over Sidney. NAM MUCAPE more unstable with a narrow band of 2000 J/KG developing near the Wyoming/Nebraska state line. HRRR/RAP simulated radar showing storms developing over the Laramie Range around the 19Z to 20Z timeframe...drifting eastward. Certainly possible for some of these storms to become supercells. Not the greatest environment...but can`t rule out a few severe storms. Large hail and strong downburst winds will be the primary hazards with these storms. Better day Monday for storms as upper shortwave tracks across the CWA and front gets forced east. Northern Panhandle seeing much better instability with MUCAPE near 2500 J/KG Monday afternoon. Much drier Tuesday as westerly winds return to the area. && .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... Issued at 111 AM MDT Sun Jun 30 2024 A cooler, active week is in store for southeast Wyoming and western Nebraska. Upper-level troughing turns upper-level winds northwesterly for Wednesday. Northwesterly flow will usher in cooler air in the region, but not without the threat for strong to severe thunderstorms. Southerly surface flow develops Wednesday, advecting in additional moisture from the Gulf of Mexico ahead of an incoming cold front. The GFS and ECMWF are both on board with a strong dryline developing off the Laramie Range Wednesday afternoon, but the exact position of this boundary is uncertain. Right now, it looks to set up along the Wyoming/Nebraska border, bringing the best storm chances to the Panhandle, with southeast Wyoming missing out once more. However, a slight westerly shift of this dryline will drastically change the output, with much of southeast Wyoming experiencing an increased chance for showers and thunderstorms. At this time, kept PoPs confined mostly to the Panhandle with low end values, around 25-40%. This setup will continue to be monitored as northwest flow tends to produce ample convection to the CWA. Westerly, upper-level flow returns to the region for Thursday through the end of the work week. Relatively benign weather is expected for the latter half of the week, with only slight chances for precipitation in portions of the Panhandle. The cold front that passes through Wednesday will drop temperatures back into the 70s and 80s for Thursday and Friday. Model disagreement returns for the weekend, with the previously advertised ridge now stuck over the Pacific Ocean just off the coast of California for the weekend. Despite this, 700mb temperatures will increase back into the 10-15C range and surface temperatures return to the 80s and 90s once more. Little to no precipitation chances exist at this time for Friday and Saturday, with significant model disagreement in play for Sunday. Kept temperatures for Sunday near the NBM, as the GFS suggests 700mb temperatures in the single digits, whereas the ECMWF keeps 700mb temperatures around 15-16C. && .AVIATION /18Z TAFS THROUGH 18Z MONDAY/... Issued at 1148 AM MDT Sun Jun 30 2024 The main aviation concern today will be scattered showers and thunderstorms currently developing in Wyoming. Multiple rounds of showers/storms will be possible this afternoon, spreading into Nebraska in the late afternoon and evening. Storms will probably struggle after moving east of the WY/NE border, so confidence is lower that they will make it to KCDR, KAIA, and KSNY. Where confidence is higher, added TEMPO groups for VIS reductions and gusty/erratic winds during the most likely time period for impacts. Storms may also bring hail. Activity should last well into the evening hours, and possibly after midnight in the NE panhandle and near KRWL. Low clouds may creep into the eastern panhandle late tonight into early Monday morning. MVFR to IFR CIGs are possible for the High Plains terminals, but confidence is highest for this occurring at KAIA and KSNY. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...None. NE...None. && $$ SHORT TERM...GCC LONG TERM...AM AVIATION...MN