Area Forecast Discussion
Issued by NWS Riverton, WY
Issued by NWS Riverton, WY
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113 FXUS65 KRIW 130424 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 1024 PM MDT Fri Jul 12 2024 .KEY MESSAGES... - Mid-summer near-record heat through Sunday. Afternoon temperatures in the 90s to low 100s will be common. - Isolated showers and thunderstorms will cause brief erratic wind gusts in the 45 to 60 mph range. - Distant wildfires across the western US will continue adding smoke to the stagnant air mass, leading to thickening smoke over much of Wyoming. - The dry air mass and breezy afternoon winds will lead to elevated fire weather danger today and into the weekend. - Temperatures moderate slightly but remain above average next week. && .DISCUSSION... Issued at 245 PM MDT Fri Jul 12 2024 The mid-summer and near-record heat will continue through this weekend as an amplified ridge remains firmly in place over the Northern Rockies. Several sites broke daily high temperatures records yesterday, and this trend is likely to continue for the next few days. A Heat Advisory is in effect east of the Continental Divide where temperatures will be hottest. Several distant wildfires throughout the Rockies and West Coast have slowly been adding smoke to the atmosphere, and given the stable and stagnant ridging pattern, smoke is likely to thicken over the weekend. The extreme heat is leading to low relative humidities, and combined with the typical afternoon breezes in the 10 to 20 mph range, there are elevated concerns for fire weather. Along with the dry heat combined with daytime breezes, there will again be a small chance (10 to 20% chance) for isolated showers and thunderstorms this afternoon and evening. Not much precipitation is expected from most of this convection, but outflow winds will likely be strong in the immediate vicinity of any downdrafts, with wind gusts on the order of 45 to 60 mph, which is enough to cause isolated damage and blown objects. The storms with appreciable precipitation will be across the far northern counties of Wyoming where higher dew points show a greater moisture availability. Across the western, southwestern and south-central portions of the state, any lightning could be outside of the wetting rain portion of storms, leading to some concern for dry lightning. These same concerns are in play for the afternoon and evening this weekend. On Monday, a slight flattening of the ridge will lead to moderating temperatures, however, daytime 90s will still be common, and temperatures remain 5 degrees or so above normal, increasing to about 10 degrees above normal for the second half of the week. So although the near-record temperatures will abate next week, the stagnant warm pattern is likely to continue for the foreseeable future. && .AVIATION /06Z TAFS THROUGH 06Z SUNDAY/... Issued at 1020 PM MDT Fri Jul 12 2024 An area of showers and thunderstorms will continue across northern portions of the forecast area and are expected to exit over Johnson County through 08Z. Skies will continue to clear, becoming mostly SKC by 12Z. Showers and thunderstorms will redevelop across the area between 20Z and 22Z Saturday. This convective activity looks to be very widespread and confidence is too low to include in any terminal forecast at this time. Conditions will likely stay VFR as well, as virga is expected with this convection. Wind gusts of 20 to 25 kt will redevelop after 18Z once again, as the lower atmosphere becomes mixed. Stronger outflow gusts could occur, if any convection moves close to a terminal. These winds will begin to subside after 01Z. The showers and thunderstorms will wane and end between 03Z and 06Z Sunday. Skies will remain hazy, as smoke from wildfires in ID, OR and CA continues to infiltrate into the area. Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for the latest information on smoke, icing, and turbulence forecasts. && .FIRE WEATHER... Issued at 245 PM MDT Fri Jul 12 2024 Hot and mostly dry conditions this afternoon and through the weekend will lead to elevated fire weather conditions over the next few days. Afternoon relative humidities drop into the 10 to 15 percent range for most lower elevations through Sunday. This, combined with westerly and northwesterly sustained winds in the 10 to 20 mph range, will lead to elevated fire weather conditions. There is a small chance (10 to 20% chance) of an isolated shower or thunderstorm causing 45 to 60 mph brief erratic wind gusts this evening. Across the western, southwestern, and south-central portions of the state, any lightning could be outside of the wetting rain portion of storms, leading to some concern for dry lightning. RH recoveries in the terrain will again be poor (in the 25 to 40 percent range) tonight for the midslopes due to thermal belts. This weather pattern persists through at least Sunday, and conditions currently don`t look to change much for next week either. && .RIW WATCHES/WARNINGS/ADVISORIES... Heat Advisory until 10 PM MDT Sunday for WYZ004>006-010-011- 017-018-020. && $$ DISCUSSION...VandenBoogart AVIATION...LaVoie FIRE WEATHER...VandenBoogart