After another unseasonably warm late October Day on Monday across Star Valley a cold front crossing the Valley Monday night will usher in a markedly cooler air mass on Tuesday. Daytime temperatures on Monday in the 50s will have a difficult time of rising above the low 40s Tuesday and remain in the 30s much of Wednesday. Most of the rain and snow with this system will likely remain to the north of Star Valley, however some light/snow could occur early Tuesday behind the cold front, most likely from the Narrows north as the cold front moves through. Any accumulation would likely be confined to the higher Salt and Wyoming Ranges, and even then only amount to an inch or so.
The greatest effect will be the colder air, officially ending the growing season across all of the Valley. By Wednesday morning the coldest regions of the valley will drop into the teens and well below freezing even in the typically milder locations such as Star Valley Ranch.
Later in the week high pressure will provide generally dry but cool conditions with a slow daytime warming trend.