-PNA/-NAO patterns like this can often look deceptively warm in the extended b/c of the SE US ridge at 500mb. However, they're notorious for sneaky backdoor cold fronts & cold air damming along the eastern seaboard, that usually doesn't show up until we're in the medium range. pic.twitter.com/Z80n1x8HiB

— Eric Webb (@webberweather) December 12, 2021