668 FXUS65 KRIW 140442 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 1042 PM MDT Tue Jul 13 2021 .SHORT TERM...(This evening through Wednesday night) Issued at 101 PM MDT Tue Jul 13 2021 Storms are expected to get ramped up later this afternoon. This morning's action was primarily just showers across the south, west, and into the Wind River Basin. These are moving into Natrona county as of 1130 AM, but beginning to wane. There will be a brief pause in activity around noon, but things will start to ramp up pretty quickly after that and continue into the later part of the evening. SPC is continuing with the slight risk of severe across the eastern zones and northern Bighorn Basin, however, an enhanced risk was added for zones just to the east, across east-central WY and southwest SD with a 30% hatched wind risk. There is a chance that this threat could cross into our area. The greatest area of concern continues to be where the slight risk areas is. A shortwave continues to rotate south out of Montana with an associated cold front. With hot, dry weather, and unstable atmosphere, this will lead to a rather eventful severe weather day. Diving deeper into the setup, MUCAPE is around 1000 to 1500 J/kg across Johnson county and the northern Bighorn basin, with decent shear. There is also 300 to 500 J/kg of CIN, which will hinder convective development initially. Once the cap gets broken, storms will develop quickly and strong to severe storms are likely. Again, the biggest threat will be wind, and and storms will likely be enhanced by outflows. large hail is also a possibility, especially across northern Johnson county. Another thing that may help to prevent convective development, at least initially will be some stabilization from the earlier showers across the Wind River basin and Natrona county. As the sun comes back out through the clouds and the surface begins to heat through the afternoon, we expect destabilization to occur and storms to begin to fire along the terrain. The dynamics will move east through the evening, along with the severe weather threats. Some storms will stick around through the late evening, likely ending between 9 PM and midnight. The severe weather threat will mostly end by 9 PM, however. West of the Divide, some storms will be possible, but much drier air exists in that area, so dry thunderstorms are more of a threat. Low RHs and gusty winds will create critical fire weather conditions by early this afternoon. Red Flag Warnings remain in effect for that area for the hot, dry, windy conditions, along with the treat for possible dry lightning. A weak thunderstorm over Rock Springs this morning has already shown us that dry thunderstorms are definitely a threat today across the south west and west. Tomorrow, looking like mainly dry and warm across the region. Today's cold front will help to moderate temperatures a bit, especially east of the Divide. Winds will also remain mainly light tomorrow as ridging begins to set in again. This will somewhat reduce the fire weather concerns, at least temporarily. .LONG TERM...(Thursday through Tuesday) Issued at 101 PM MDT Tue Jul 13 2021 The overall pattern across the western US changes little during the next several days, but looks to amplify as we go into the weekend. The H5 ridge remains in place along the Intermountain West, with broad westerly flow aloft across WY. Since the ridge is not yet strengthening, convection will be able to fire along the higher elevations during peak daytime heating. While activity will be widely scattered, there will be the threat for occasional lightning and very gusty winds. Starting Saturday, the ridge will buckle northward, with models settling the center of the ridge across western WY through the weekend. The stronger ridging will help cap off convection, and will bring higher temperatures statewide into early next week. The main question in this forecast is whether a cutoff low dropping across the central Plains will block this ridge from shifting east, or remaining in place through the remainder of next week, continuing the heat across the state. && .AVIATION...(For the 06Z TAFS through 06Z Thursday) Issued at 1030 PM MDT Tue Jul 13 2021 Expect VFR conditions to be across the area during the TAF period. Any lingering showers should end by 09Z. Very isolated showers or storms may occur in far southern WY Wednesday afternoon into the early evening. Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for the latest information on icing and turbulence forecasts. && .FIRE WEATHER... Issued AT 101 PM MDT Tue Jul 13 2021 Scattered showers and thunderstorms will continue across the state today, with the dry lightning threat continuing mainly for far northern WY and southern WY. Any storms that do form will also bring a threat for gusty winds. Southern WY will also see humidity levels well below 15 percent through the day, with widespread gusts above 30 mph. The system bringing the increase in thunderstorm activity will move east tonight, with lighter winds returning on Wednesday. The only areas with gusty winds will be limited to far southwest WY across zones 277 and 279. Isolated thunderstorms will try to develop on the higher elevations of the western and northern mountains Wednesday afternoon, but will be very isolated in nature. && .RIW WATCHES/WARNINGS/ADVISORIES...None. && $$ SHORT TERM...Fisher LONG TERM...Straub AVIATION...Clayton FIRE WEATHER...Straub