Area Forecast Discussion
Issued by NWS Cheyenne, WY
Issued by NWS Cheyenne, WY
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307 FXUS65 KCYS 132148 AFDCYS Area Forecast Discussion National Weather Service Cheyenne WY 348 PM MDT Mon May 13 2024 .KEY MESSAGES... - Chances for scattered showers and thunderstorms Monday and Tuesday. - A cold frontal passage is expected on Wednesday, with much of the region returning to below-normal temperatures and increased chances for rain and high-elevation snow. - Warming temperatures through the end of the week with a dry start to the weekend expected. && .SHORT TERM /THROUGH TUESDAY/... Issued at 343 PM MDT Mon May 13 2024 Current radar and satellite show showers developing over the high terrain. As the afternoon progresses, expect these showers to push eastward into the high plains through the evening. There is some instability across the area, so thunderstorms with small hail could be possible, but the main impact with storms will likely be strong, gusty winds, as the surface and low-levels remain quite dry. A brief break from storms is likely overnight. Over the next two days, two shortwaves will move across the CWA, bringing more rain and storm chances. Models, especially CAM guidance has really trended precipitation down compared to some of the global models. As a result, did trend PoPs down on both Tuesday and Wednesday as the NBM seemed quite aggressive. Focusing in more on Tuesday, most of the shortwave will pass just north of the CWA. This will spark convection throughout most of the day for the northern tier of the CWA. Later in the afternoon, instability will build, causing convective initiation over the high terrain. Severe weather looks unlikely as there isn`t enough strong instability present. However, still could see gusty winds and small hail. Next shortwave arrives Tuesday night, bringing with it a cold front and more moisture. Temperatures on Wednesday will be about 10 degrees colder behind the front. Again, more scattered showers and maybe a thunderstorm or two will be possible. There is not as much instability present with the cooler temperatures, so expecting mostly rain showers. && .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/... Issued at 343 PM MDT Mon May 13 2024 Medium to long range models in better agreement compared to yesterday with still some large ensemble spreads for later this weekend. 12z ECMWF is no longer showing a strong cold front pushing across the high plains into southeast Wyoming on Thursday as the trough axis is much further north near the United States/Canadian border. Models show northwest flow aloft initially early on Thursday before it transitions to westerly flow by Friday. Expect another warming trend to end the week as afternoon temperatures climb into the 70s across most areas of southeast Wyoming. Western Nebraska will likely climb well into the 80s Friday afternoon. With drier westerly flow expected, kept minimal POP outside of the mountains with a few sprinkles possible. Warm than average temperatures will likely continue into next weekend with all models showing a flat upper level ridge quickly progressing eastward over the Great Plains and zonal flow over the western third of the country. Another cold front will quickly move across Wyoming, but models are in considerable disagreement on when this may be. The 12Z ECMWF and Canadian are a full 24 hours behind the 12z GFS and show FROPA on early on Sunday instead of Saturday. GEFS and ENS ensemble forecasts show a large spread in temperatures, but this time later in the weekend/early next week compared to yesterday. Gradually decreased temperatures late this weekend and into next Monday with increasing cloud cover and chances for showers/thunderstorms in the afternoon. Chances for strong to severe thunderstorms appears very low at this time. && .AVIATION /18Z TAFS THROUGH 18Z TUESDAY/... Issued at 1150 AM MDT Mon May 13 2024 A stationary front is forecast to drift east today across the high plains, but then return westward towards the Laramie Range early tonight. Convergence and instability near this boundary will result in scattered showers and isolated thunderstorms into this evening, mainly for southeast Wyoming. HAZARDS/WEATHER TRENDS: VFR conditions are expected to continue this afternoon and tonight with occasional mid to high cloudiness. KCYS has the best chance to see an isolated thunder shower this afternoon and this evening, with lower probabilities for KLAR and KBFF. Breezy conditions expected this afternoon for the southeast Wyoming terminals, with increasing south winds between 04z and 11z tonight for KCDR. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...None. NE...None. && $$ SHORT TERM...TJT LONG TERM...SF AVIATION...TJT