


Area Forecast Discussion
Issued by NWS Riverton, WY
Issued by NWS Riverton, WY
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383 FXUS65 KRIW 161843 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 1243 PM MDT Thu Oct 16 2025 .KEY MESSAGES... - Mountain snow and low elevation rain continues through the afternoon. Winter travel conditions over mountain passes. - Precipitation ends from this evening through about midnight. Light mountain snow lingers through about sunrise Friday. - Warmer and drier conditions on Friday. - Saturday through early next week will remain unsettled with an additional system or two bringing precipitation chances to the area. && .UPDATE... Issued at 1242 PM MDT Thu Oct 16 2025 Forecast remains on track, with lower elevation rain and mountain snow through tonight. Heaviest mountain snow occurs late morning through this afternoon, impacting mountain passes and high elevation roads. Precipitation chances end for most locations by about midnight, with lingering snow over the mountains through Friday morning. Precipitation chances and amounts have been adjusted with latest model trends, but no notable changes were made with this update. && .DISCUSSION... Issued at 434 AM MDT Thu Oct 16 2025 The forecast in the short term will continue to be dominated by a highly amplified trough and associated upper low that is now moving into southern Wyoming. Ongoing jet-induced showers and thunderstorms will be bolstered by sunrise as the low moves farther northeastward into central Wyoming. Colder air is concurrently moving east across the state this morning. Precipitation is expected to become fairly widespread by mid-morning, wrapping cyclonically around the low and steadiest across central Wyoming and over any mountains. Snow levels will drop to around or just under 7,000 ft this morning, which could at least briefly bring light accumulations to elevated surfaces across western Wyoming and the Green River Basin. Winter Weather Advisories remain in effect for most of the mountains through this evening. The Bighorns continue to be the exception, with most of the accumulation there expected to be along the higher peaks of the Cloud Peak Wilderness. Travel impacts due to snow should remain limited to the mountain passes across the area. Precipitation will begin to wane by sunset today as the low moves into northeastern Wyoming and drier air pushes in behind it. Johnson County and the eastern Bighorn Basin will likely hold on to precipitation the latest before most of this activity comes to an end by midnight. Light snow may continue overnight across the mountains of northwestern Wyoming though with little to no additional accumulation. Total liquid precipitation amounts through the rest of this system will be highest along the track of the low from northern Sweetwater County through Johnson County. These areas will generally have around a 50 to 70 percent chance of at least a quarter of an inch and a 30 to 50 percent chance of at least a half inch. Westerly wind will increase Friday morning in the wake of the system as surface pressure decreases to our east. Temperatures will moderate Friday afternoon and no precipitation is expected. Guidance is then keying in on a glancing blow from a trough to our north arriving Friday night. This should bring a cold front and a quick shot of moisture through Saturday morning along and east of the Continental Divide. By Saturday afternoon this feature should already be east of the area, with ridging settling in behind it. Accordingly, Sunday is favored to be warmer and drier. However, guidance is showing yet another system arriving Sunday evening. This one appears a little more substantial and may return more widespread precipitation chances to the area early next week, including mountain snow. && .AVIATION /18Z TAFS THROUGH 18Z FRIDAY/... Issued at 1035 AM MDT Thu Oct 16 2025 A cold winter storm is current moving from southwest to northeast through the forecast area today, bringing a variety of weather to the TAF sites, as well as conditions ranging from VFR to VLIFR. Complex weather along with varying ceilings and visibilities will continue through the afternoon into the early evening hours before the main impacts move into northeast WY and the northern Plains. A few locations pose an uncertain forecast today. At KCOD, models are indicating gusty west winds developing at some time between 09z-15z tomorrow as stronger mid-level northwest flow moves over the area, but difficult pinning down the timing. KCPR will be gusty at times from the west with showers this afternoon, and remain that way overnight with the trough passage. Have included a chance of fog at both KJAC and KWRL based on model indications, though wouldn`t be surprised if more sites are impacted by patchy fog early tomorrow morning based on today`s precipitation. The rain/snow line is right at KRKS at this time, and will continue with IFR snow conditions for the next hour or so, with snow/rain showers this afternoon. Friday will see isolated showers over the western mountains, though gusty west-northwest winds are expected in the post- storm environment at most TAF sites. Clouds will increase again from the northwest to southeast late Friday into Friday night as a weak storm system approaches from the PacNW. 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... Winter Weather Advisory until 11 PM MDT this evening for WYZ002-012-014-015-024. && $$ UPDATE...Wittmann DISCUSSION...Myers AVIATION...McDonald