Area Forecast Discussion
Issued by NWS Riverton, WY
Issued by NWS Riverton, WY
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452 FXUS65 KRIW 251524 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 924 AM MDT Sat May 25 2024 .KEY MESSAGES... - An unsettled start to the holiday weekend with scattered showers and isolated thunderstorms spreading from southwest to northeast. - Conditions improve after that, with showers restricted to the north and east Sunday. - After a dry and pleasant Memorial Day, unsettled weather returns for midweek. Details on timing of precipitation this far out remains uncertain. && .DISCUSSION... Issued at 250 AM MDT Sat May 25 2024 Long time residents of western and central Wyoming know that Memorial Day weekend is known for being rather unsettled and wet, and at times cold with snow. And, portions of this weekend will be no exception. But there is not all bad news. The good news is that all areas will have at least one nice and dry day, and many areas will have two. The bad news is most areas will not have all three remain dry. Satellite imagery is showing some moisture moving into the area as I write this around 2 am. The chance of showers and thunderstorms today looks to progress from southwest to northeast, with areas with like Buffalo and Casper seeing it last. As for the strength of storms, there is some CAPE (Up to 500 J/Lg). However, lifted indices only top out around minus 2 and there is not a ton of jet support. Clouds spreading over the area will also limit instability somewhat. For today, it looks the western and southern portions of the area will see the most showers and storms today (topping out at around a 3 in 4 chance) with tapering chances further east (dropping to less than a 1 in 5 chance). Many area East of the Divide may be dry most of the day. With the cloud cover, temperatures will average slightly below normal. And yes, in the mountains above 8000 to 8500 feet, there will probably be some snow, but amounts should remain light for the most part. The Pacific system bringing the showers will move across the state tonight, and the chance of showers will shift more northeastward, with southern Wyoming drying out. A trailing shortwave will then brush by northeastern portions of the area. This wave has little moisture to work with, but does have better upper level support with a 90 knot jet moving into northern Wyoming. This will bring another chance of showers and thunderstorms across roughly the northeastern third of the area, roughly north of a Jackson to Thermopolis to Casper line. Areas further south will likely have a dry day. There will be enough downward momentum from the right front quadrant of the jet to bring a gusty breeze, the central Wyoming, but nothing close to high wind is expected. As for chances of showers, they range from around 2 out of 5 around Buffalo then lessening southwestward, with higher POPS in the mountains. These showers should end fairly quickly Sunday evening. Monday definitely looks like the nicest day of the holiday weekend as ridging moves over Wyoming and brings a day of sunshine and near normal temperatures. Uncertainty then increases from later Tuesday through much of the week. The ridge then shifts east as another upper level low moves onshore in the Pacific Northwest and moves eastward. Guidance remains divided on the timing of the shortwaves and how far south impacts can set in this area. Odds definitely favor northern Wyoming at this time. But details on timing of the waves and how far south showers can get remains in flux. && .AVIATION /12Z TAFS THROUGH 12Z SUNDAY/... Issued at 457 AM MDT Sat May 25 2024 VFR conditions for all TAF sites to start the period. Light winds and mid level clouds throughout the CWA as an approaching system comes in from the southwest. Afternoon thunderstorms and gusty winds expected for most between around 20-01Z with less confidence at WRL, RIW, and LND not carrying a tempo for TSRA at this time. With thunderstorms on station will come possible MVFR ceilings around 2500` IAW BUFKIT soundings and forecast LCL heights. Otherwise, any activity should end by 01Z towards sunset and radiational cooling overnight. Light winds and mid level clouds continue through the end of the period with no other weather elements expected at this time. Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for the latest information on icing and turbulence forecasts. && .RIW WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Hattings AVIATION...Lowe