Expires:No;;872971 FXUS65 KRIW 061724 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 1124 AM MDT Sun Apr 6 2025 .KEY MESSAGES... - Sunny, dry, and seasonal to warm temperatures today and tomorrow. - Breezy Monday, then widespread gusty winds 25 to 35 mph Tuesday and Wednesday, with higher gusts for favored locations. Combined with low relative humidities, elevated fire weather conditions are possible. - Precipitation chances late Monday through Wednesday, favored for western and northern Wyoming. Thunderstorms possible. && .DISCUSSION... Issued at 109 AM MDT Sun Apr 6 2025 High pressure is in place today. As a result, temperatures will trend up, with highs forecasted in the 50s west of the Continental Divide (upper 40s for western valleys), and upper 50s to mid-60s east of the Divide. These temperatures are just a few degrees above normal for early April. Some passing high clouds move through, but otherwise a mostly clear sky and dry conditions persist through the day. Afternoon relative humidities (RH) will again be dry, ranging from around 15 percent to 25 percent across the area. North to northwest winds today will bring some breezy gusts (15 to 25 mph) for some areas, like the Green River Basin and from around Buffalo to Casper. The ridge axis passes over the area Monday, meaning the warmest temperatures associated with this high pressure system. Highs trend 3 to 8 degrees warmer than they will be today. Later in the day, the next approaching weather system begins to flatten the ridge. This tightens the pressure gradient, so increasing afternoon winds will occur across the Wind Corridor and higher elevations. Afternoon gusts from about South Pass to Casper will generally be 30 to 40 mph. A broad trough then moves through late Monday through Wednesday. This will bring two main weather elements, precipitation chances and wind. Starting with precipitation, chances begin across western Wyoming around 6pm MDT, spread eastward into Monday night. Models continue to favor chances over western and northern Wyoming. Initial precipitation type may be snow or rain/snow mix for the western valleys, with snow for the mountains; daytime highs will mean rain for the valleys and basins. Overall, not expecting a great amount of rain or snow, with model NAM PWAT values around 100% of normal. Precipitation chances continue through Wednesday, with highest totals currently forecasted for the Tetons, Yellowstone, and Absarokas, where snow totals are generally under 7 inches (isolated higher amounts). This is still subject to change in the next couple days as better high resolution guidance becomes available. Some instability may also produce thunderstorms Tuesday and Wednesday. The other element is wind. Winds increase Tuesday morning. Some decrease is expected Tuesday night, before increasing again for Wednesday. Probabilistic guidance favors Wednesday to be the slightly stronger wind day, but both days will be quite windy, with widespread gusts 25 to 35 mph Tuesday, with a little higher for Wednesday. Favored areas, like the Wind Corridor or central mountains, will likely see higher winds. As mentioned previously, moisture will be limited with this system, so afternoon RHs will be on the dry side, with values of 18 to 30 percent Tuesday and Wednesday. This could bring areas of elevated fire weather conditions, with wind being more more influential factor as RHs are more marginal. High pressure then returns for the end of the week. Model 700mb temperatures would support Friday or Saturday being the warmest day. With this, river rises are looking likely with snow melt. However, this is fairly typical for this time of year, and with normal-ish mountain snowpack (most water basins around 100% snow water equivalent amounts) and no large precipitation events expected, there is little concern for flooding at this time - so expect just typical, spring river/creek rises associated with snowmelt. Long range models hint at another system for the end of next weekend into early next week, which would favor cooler temperature and maybe precipitation. As expected this far out, details are lacking. && .AVIATION /18Z TAFS THROUGH 18Z MONDAY/... Issued at 1123 AM MDT Sun Apr 6 2025 Dry and VFR flight conditions persist this TAF period with high pressure overhead. Expect winds to remain relatively light (10 knots or less) at most terminals. The exceptions are KBPI, KPNA, KRKS, and KCPR, where those terminals will likely see winds around 15 kts with periodic gusts around 20 knots before diminishing after sunset. Winds at KCPR and KRKS are forecast to increase again around sunrise Monday. Otherwise, only FEW high cirrus are expected. 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...Wittmann AVIATION...Gerhardt