Today I hop on my bike after a class and start to ride and I notice that my drivetrain feels and sounds like it is grinding or like there is sand in the drivetrain. I rode earlier in the day with no problem and rode just before the class for about a half hour and didn't notice anything. I instantly figured it was just grime in the chain (in oregon and it's crappy right now) but pulled over to give it a quick look and make sure I was not missing something terrible. I found a loose chainring bolt and tightened it down I also grabbed some paper towels and gave the chain a quick wipe and hit the chainring and cog as best I could. I hop back on and continue my ride but it is still there. I live in Oregon and ride in rain and deal with road grime all the time but never felt this before. I tend to clean and lube my chain at least every 2 weeks but usually more. So am I missing anything or should I just clean and lube when i get home?

edit: I just remembered it snowed about a week ago and the roads were sanded. I've ridden on them for a week though and it just happened today after being parked during class.