Edit: This question is for U.S English as I know that coordinating conjunctions in British English don't need a comma.
After reading an article about adverbial conjunctions, I've noticed a peculiar thing when the adverbial conjunction was used to end a sentence.
"We wanted to go on a picnic. The weather turned bad and we
weren't able to go, however."
The last sentence have two independent clauses, so shouldn't there be a comma after the word "bad" as it's a run-on/comma splice?