775 FXUS65 KRIW 050741 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 141 AM MDT Sat Jul 5 2025 .KEY MESSAGES... - Chances for showers and thunderstorms Saturday with another chance for severe storms, especially in the Bighorn Basin, the Bighorns and northern Johnson County. Hail and strong winds are the main hazards. - Drier weather returns Sunday, with warmer conditions and increasing chances for elevated fire weather from Monday to Wednesday. && .DISCUSSION... Issued at 133 AM MDT Sat Jul 5 2025 Showers continue to end across the CWA early this morning and are expected to dissipate no later than sunrise. Clouds will scatter out through this time with only high clouds over far western portions. This would leave mostly clear skies for the rest of the area, which could lead to the possibility for fog (especially lower lying areas along the rivers and creeks). However, any fog that would formed would be short-lived due to the approaching system. A shortwave trough will move across the northern half of the CWA today, providing sufficient lift and upper level divergence for showers and thunderstorms. This activity will mainly occur east of the Divide, but will extend over the Wind River Mountains and the northern half of the Upper Green River Basin. Low level moisture will remain in place this morning, with dewpoints in the 40s to middle 50s for most areas today. Low level lapse rates of 7 to 9 C/km will be prevalent as well, along with lifted indices of minus 4 to minus 6. Mixed layer CAPE of 500 to 1500 J/kg and bulk shear of 30 to 40 kt will all combine for another day for strong to severe thunderstorms. The Bighorn Basin will have the best chance for these storms moves through the area between 19Z and 00Z. This line will quickly push eastward over the Bighorns and northern Johnson County by 22Z and exit the CWA after 01Z. Wind gusts of 60 to 70 mph is expected again with this activity (similar to what occurred Friday), but large hail (1 inch or higher) cannot be ruled out. Additional showers and thunderstorms will develop from the Wind River Basin to the Upper Green River Basin (as previously mentioned) as the tail end of the shortwave moves over the area. These storms are not expected to be as severe, but wind gusts up to 60 mph could still occur along with small hail. No showers or thunderstorms are expected over Sweetwater County or southern Lincoln County, due to a lack of instability. Convection will exit the area by sunset with only isolated showers remaining possible through 06Z, mainly over Natrona County. A weak cold front from the shortwave will drop southward over areas east of the Divide during this time, quickly reaching the Divide and into the Wind River Basin by 09Z. This will only result in the obvious wind shift and slightly dropping temperatures a few degrees Sunday morning. The passage of this shortwave will mark the end of this latest active weather pattern, as drier air moves into the region. Flat ridging will be in place Sunday, with the front washing out through the day and keeping daytime temperatures similar to today. The focus will shift to fire weather, as an upper level ridge builds over the region from a strengthening high center over the Four Corners. Winds look to remain light through Wednesday, however 90 degree temperatures will return by Tuesday for areas east of the Divide. Locations on the east side of the Bighorn Basin, such as Greybull and Worland, could possibly reach 100 degrees by Wednesday. The next chance for precipitation looks to occur Thursday,as a remnant low moves over the northern side of the Four Corners high. This would lower temperatures a bit an d cause the high to retreat further south. There is a chance this low comes in phase with trough that will pass over southern Canada. This could lead to more widespread precipitation chances, but will have to see how to forecast evolves over the coming days. && .AVIATION /06Z TAFS THROUGH 06Z SUNDAY/... Issued at 1046 PM MDT Fri Jul 4 2025 Showers and embedded thunderstorms will continue moving east through midnight, possibly bring wind gusts to 40 knots in vicinity of KWRL and KCPR as they pass. Otherwise, VFR flight conditions are anticipated with clearing overnight skies and light winds. South to southwesterly winds increase at all terminals between 17Z-19Z with gusts generally between 20-25 kts. Scattered showers and thunderstorms are possible (30 percent chance) Saturday between 20Z-01Z at most terminals; however, confidence in direct impacts is around 30% so opted for a PROB30 group at this time. Confidence (less than 20%) is lower at KJAC, KLND, and KRKS so left any mention out at this time. Any direct impact or nearby thunderstorm could produce gusty winds over 35kts. Outside of thunderstorm gusts, daytime gusty winds are expected to diminish around sunset Saturday evening. Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for the latest information on smoke, icing, and turbulence forecasts. && .RIW WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...LaVoie AVIATION...Gerhardt/Hattings