Area Forecast Discussion
Issued by NWS Riverton, WY
Issued by NWS Riverton, WY
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272 FXUS65 KRIW 262040 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 240 PM MDT Wed Jun 26 2024 .KEY MESSAGES... - Showers and a few thunderstorms continue to bubble across the state. Some thunderstorms may contain gusty winds. - A more widespread threat for stronger thunderstorms expected on Thursday for nearly all of the state. Western and Central WY will have the threat for very gusty winds and hail. - Ridge builds back across the state for the weekend, with a return of much warmer and drier conditions. Gusty winds will increase the fire weather threat both Friday and Sunday. && .DISCUSSION... Issued at 202 PM MDT Wed Jun 26 2024 Shortwave continues to transit the state this afternoon, with enough instability to spark a few showers. Main push has been held back until current time due to building of daytime heating, but more convective activity is setting up across central WY, and another area developing quickly in NE ID. SPC did bring a marginal sever threat into far NW WY this afternoon, with gusty winds being the main threat. Any precip should be fairly light, but a brief downpour may occur in stronger storms. Thursday turns to a more potent day across the state as a larger trough sweeps in off the PacNW Coast into the far southern Canadian Prairies. Ahead of the trough, sfc moisture will be building across the state, with dewpoint temperatures starting the day in the 50s. Related PW values running 2 to 3 standard deviations above normal indicate plenty of fuel to generate thunderstorms. Mostly clear morning skies will help quickly destabilize this layer. As the trough sweeps to the east during the day, diffluence ahead of the trough will bring good lifting aloft, tapping the unstable sfc moisture layer. drier air aloft will try to wrap in from behind during the afternoon, trying to form a modest dryline-type boundary advancing across the state. Storms would be able to tap the approaching 100 jet to mix very gusty winds down to the sfc. Some hail is also a threat, but this may be confined farther north closer to the cold pool near the trough center. SPC already has marginal SVR risk for nearly all of western and central WY, with slight risk just to the east of the I-25 corridor. Main forecast issue is where storms fire first. Initial showers may already form along the WY/ID border midmorning, but the main building will probably fire along the western mountains and quickly push east during the afternoon, tapping the unstable sfc moisture. The thunderstorm activity will be moving quickly, so most activity should be well off to the east and southeast by early evening. Friday will see the trough continue east into the Northern Plains. Some lingering moisture and daytime heating may bring a few showers along the higher elevations of the Bighorns, and for southeastern Sweetwater County, but most other will see a nice day with temperatures in the 70s and 80s. Friday will be windy and drier, so some fire weather concerns may develop during the afternoon. Saturday and Sunday will continue the warming and drying trend, with temperatures back in the 90s. Sunday will see gusty winds again in advance of the next trough sweeping into the PacNW, so more fire weather concerns are noted here, as gusts could approach 40 mph at times, while humidity levels fall to near 10 percent. Still watching with interest that next trough for late Sunday and Monday. Current forecast does bring a good amount of Pac moisture with it, but strongest lift occurs overnight, so peak heating will be minimized as it passes. && .AVIATION /18Z TAFS THROUGH 18Z THURSDAY/... Issued at 1122 AM MDT Wed Jun 26 2024 Shower and thunderstorm chances continue to spread eastward through the afternoon. All sites have at least a 15% chance to see a shower or thunderstorm today. Locations with closer to 30% chances have TEMPO or PROB30 groups in the TAFs. Shower chances will persist overnight, but will be less than 20% for all terminals (except KRKS) after 03Z. KRKS has the best chance to see thunderstorms after 03Z. Then, shower and thunderstorm chances increase again late in the period. West to southwest winds also increase late Thursday morning as a shortwave passes through the area. 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...Straub AVIATION...Hensley