857 FXUS65 KRIW 110433 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 1033 PM MDT Sun Aug 10 2025 .KEY MESSAGES... - Mostly clear and cool overnight tonight for western and central Wyoming. - Lighter winds and mostly dry conditions over the next 3 to 5 days with a warming trend through mid-week. Wednesday and Thursday look to be the hottest days of the week. - Fire weather concerns return for Wednesday and Thursday as winds increase. && .UPDATE... Issued at 1255 PM MDT Sun Aug 10 2025 A few showers and isolated thunderstorms continue to persist across Johnson County this afternoon. These are associated with a shortwave digging out of MT on the backside of the longwave trough that is now centered over the northern Plains. Increased PoP coverage across Johnson County as there is a bit more moisture to work with today (PWATs around 0.8"), but generally kept as isolated (15% chances) as model guidance still struggles to resolve any longer duration storms or showers. There is a slight chance (10%) that these showers and storms could also initiate off of the southern Bighorns and Casper Mountain, which would track into Natrona County, so have added some weak PoPs there as well. Otherwise, not much change to the forecast as we see the ridge start to re-establish itself over the coming days and thus, the weather pattern will remain generally quiet. Elevated fire weather does continue, but light winds will be the limiting factor through at Tuesday. && .DISCUSSION... Issued at 224 AM MDT Sun Aug 10 2025 Things are largely quiet on this 2nd sunday of August. A weak mid level disturbance is producing a few blips on the radar across the Wyoming - Montana border but these are producing only a few sprinkles and should be on by shortly after sunrise. Otherwise, it looks like a nice day for most with comfortably warm temperatures and a sunny to partly cloudy sky. The only exception is across portions of Natrona and Johnson County where a subtle shortwave and maybe just enough mid level moisture may bring isolated showers or thunderstorms this afternoon (generally a 1 out of 6 chance). Most places won`t see one though. And most importantly, a light to moderate wind across most of the area so this is the first day in a while we have not had any fire weather concerns. No concerns on Monday as ridging will control the weather, bring dry conditions and light to moderate wind. Temperatures will warm through, but only to near to slight above normal. On Tuesday, models have slowed the progression of the next front. This should lead to lighter wind and as a result; fire weather looks like less of a concern. A very weak shortwave may brush by far northwestern Wyoming and could bring an evening shower or thunderstorm, but the chance only looks like about 1 in 10 at this time and we kept the forecast dry for now. Concerns begin to ramp up again on Wednesday as the front moves closer to the area. This will tighten up the pressure gradient and turn flow to the southwest. This means stronger wind across portions of the area, especially the southwestern Wind Corridor from Rock Springs through Casper. This will also warm temperatures significantly, the widespread highs in the 90s, possibly the upper 90s, in areas East of the Divide. Humidity will be low enough for critical fire weather, but wind still looks borderline in some locations. Enough mid level moisture may return to western Wyoming for isolated thunderstorms, but the chance is generally less than 1 out of 5 and most locations should not see one. The most concerning day for fire weather looks to be Thursday as the front and shortwave approach, bringing the breeziest conditions. Convection may be a bit more this day, but with the lack of low level moisture coverage stills looks rather sparse at this time. Somewhat cooler temperatures should return for Friday and Saturday, but temperatures will still be near to lightly above average across the area. && .AVIATION /06Z TAFS THROUGH 06Z TUESDAY/... Issued at 1031 PM MDT Sun Aug 10 2025 VFR conditions tonight with light winds and only a few high cirrus floating through. Most of western WY will stay skc/sct150 through the day Monday, with light north winds. A few showers are again possible from KCPR to KBYG after 18Z, but will be even more isolated than today, and any impacts at these airports will be minimal and brief. Chances still too low to add any notation to TAFs for the moment. && .RIW WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Hensley DISCUSSION...Hattings AVIATION...Straub