An interesting forecast ahead. A cold plunge of air will shift in for Friday keeping temperatures only in the 40s for most of the day across the valleys, and only in the 30s over the mountainous areas. A chance of rain showers in the valleys, will mix with snow by mid morning over the mountains. Snow levels look to come down to about 1500'. BUT there is an asterisk there! With any amount of precipitation, the freezing level may drop even lower to about 1000' elevation! Don't be surprised if you see your first snowflakes of the season Friday. I will be excited if we get to see some graupel (soft, styrofoam-like snow). (see image top left-snowfall forecast)
Admittedly, afternoon high temperatures will be a tricky and bustable forecast as that colder air fills in. I am sticking with an afternoon high of 48 for now. Should that happen, this will be the coldest day in the Champlain Valley since late April of this year! It should also be noted that the record for coldest maximum daily temperature on the date of October 12 is 41 degrees F.
Carry that cold air into Friday night and you've got the end of the growing season with widespread frost likely. As temperatures dip back into the upper 20s around my point of forecast (South Burlington – Burlington Int'l Airport), this will also be the coldest night since late April as well. A hard freeze is likely in many spots by Saturday morning.
Some exceptions to the rules Friday night....the water on Lake Champlain is still quite warm. The latest water temperature readings on the Lake show near shore temperatures in the upper 50s still. This extra heat should allow temperatures to stay a bit warmer right near the shorelines of the Lake. I estimate there is a 1-2 mile "buffer zone" away from the shorelines that will keep temperatures in the lower to mid 30s by Saturday morning. Still, a light frost could occur here.