483 FXUS65 KRIW 140834 AFDRIWArea Forecast Discussion National Weather Service Riverton WY 234 AM MDT Sun Sep 14 2025
.KEY MESSAGES...
- Partly to mostly sunny today, with mild September temperatures.
- Next weather system sweeps across the state starting tonight, bringing more showers and thunderstorms for Monday into Tuesday.
- Temperatures begin to cool around midweek, with some lowlying areas west of the divide approaching freezing.
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.DISCUSSION... Issued at 209 AM MDT Sun Sep 14 2025
The broad trough continues to slowly try to shift east, with multiple embedded impulses rotating through it. The latest wave is sweeping into western Nebraska/South Dakota this morning, with some wraparound precip trying to form back into Natrona County. This precip has been very light, if reaching the ground at all, and will quickly exit back to the east by midmorning. The gap between systems today will allow most areas to see partly to mostly sunny skies and warm temperatures back into the 70s and lower 80s.
WV imagery shows the next weather system currently coming ashore across Oregon. This system will come rotating around the bottom of the trough and into western WY late tonight, spreading the next round of showers and thunderstorms into the region. Models continue to bring this trough eastward, then stalling it across western WY through Tuesday. This will continue the high likelihood of showers and thunderstorms into Tuesday. With the overarching trough nudging eastward as this arrives, the remaining portion of the smaller system then shunts southward late Tuesday and Tuesday night. This also brings modest northerly flow behind it, bringing slightly cooler air into the state. Temperatures will cool enough to approach near freezing west of the divide in lower valleys and basins Tuesday night.
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.AVIATION /06Z TAFS THROUGH 06Z MONDAY/... Issued at 951 PM MDT Sat Sep 13 2025
A brief reprieve from convective activity will occur over the next 24 hours. Conditions will remain VFR with mostly clear skies through the TAF period. The next weather system begins to move into western Wyoming Sunday evening, with rain showers possible (30%) by 04Z/Mon at KJAC. Other terminals will remain dry through the TAF period.
Wind will be a bit gusty for several terminals Sunday afternoon. In general wind will be 8-13 knots, with gusts of 18-23 knots Sunday afternoon and light otherwise.
Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for the latest information on icing and turbulence forecasts.
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.RIW WATCHES/WARNINGS/ADVISORIES... None.
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DISCUSSION...Straub AVIATION...Rowe
NWS riw Office Area Forecast Discussion