


Area Forecast Discussion
Issued by NWS Riverton, WY
Issued by NWS Riverton, WY
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204 FXUS65 KRIW 170401 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 1001 PM MDT Thu Oct 16 2025 .KEY MESSAGES... - Precipitation ends around 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 /06Z TAFS THROUGH 06Z SATURDAY/... Issued at 958 PM MDT Thu Oct 16 2025 The main concern will be the potential for fog development tonight into Friday morning. This will be highly dependent on where skies clear and wind is light. KJAC and KWRL have the best chance of fog development from about 10-14Z Friday morning. For now have kept the TEMPO groups at the aforementioned terminals. For KWRL there may be too much cloud cover overnight for fog development. Other terminals that have a chance (15%) are KRIW and KLND due to skies already clearing and light wind. Not a high enough chance (15%) for any mentions in the TAFs at this time. MVFR CIGS at KRKS should slowly lift tonight as the weather system moves well to the east of the area. Have added a PROB30 group at KCOD for -SHRA and MVFR conditions starting at 05Z Sat as the next weather system begins to push in from the north by that time. Rain chances will increase across northern Wyoming Friday night, but rain showers will be scattered. Wind will remain elevated at KCPR and KRKS through the TAF period. KCPR will have a noticeable wind increase, with gusts of 25-30 knots early Friday morning as the pressure gradient tightens ahead of the approaching weather system. Most terminals will have a gusty wind Friday afternoon. A cold front will bring a wind shift at KCOD and KWRL late Friday evening, becoming northwesterly. Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for the latest information on icing and turbulence forecasts. && .RIW WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Wittmann DISCUSSION...Myers AVIATION...Rowe