Most definitely the barometric pressure plays a role in how bad the RSD/CRPS will be. Usually I can tell a day or two before the front actually hits. I have also monitored using weather underground’s site, and for us here in Colorado we typically have a daily drop in the afternoon especially during monsoon season. In Colo we are so high up in altitude (a mile above sea level or 5280 feet) that I feel even the slightest drop like the daily one we get. But boy oh boy if a system is pushing through and the ceiling drops (barometric pressure) a lot, I will feel this a day or two before it arrives. My husband and I laugh that I should really consider a career in meteorology.