Local weather forecast is pretty decent for Friday and probably Saturday. Raining here in Brockton right now, 35 minutes from Rausch.
I-81 will be one lane in each direction for the foreseeable future, worst times of the day are mid afternoon- evening and of course traffic on Friday is usually busier than other days. I believe the two lane setup starts around MP97 or so below the pine grove exit and ends shortly below exit 107. There is no real short detour around the two lane area.
One bypass would be to go straight onto I-78 where 81 and 78 split, then take the 501 north exit into Pine Grove. 501 tees into 895 in PG, turn left at the tee and you'll hit 443 the main drag in Pine Grove. Turn right and drive through pine grove on I think route 125 (route 443 turns right at the intersection with 125). This will take you through town and up to the area of exit 104 where you can turn left past the truck stop and up the hill to Rausch. Please note that route 501 between I-78 and PG goes over a short but fairly steep mountain, takes you right over the Appalachian trail. It ain't shorter for sure than I81 but will help you avoid the construction area.
From PG north is the familiar back way from Twin Grove to RC.