I find the 20F-35F range most difficult to figure out, even though that's what we get the most of. If you prepare for wet weather, you get hit with wind and extreme cold. If you prepare for extreme cold, you get hit with wind and rain. So you gotta prepare for both, then you get warm sunny weather and no wind. lol

I suggest bringing a thermometer so you can be objective about what you actually encounter, and wear the clothes you actually want to test, and keep some emergency clothes stashed deep in you pack just in case. Long underwear are good emergency clothes because they usually fit well in between the skin layer and mid layer that your testing. The goretex jacket sounds like great insurance also. I would be happy to stick with that until I found something lighter that was exactly what I want. Currently I use a 4oz cheap nylon wind shell as a wind layer and a cheap sylnylon poncho/tarp as my rain layer / shelter. I have a HEAVY military gortex bivy sac that I've been thinking of converting into a rain cape / bivy, then maybe get a different tarp.

Have a great weekend.