I asked ChatGPT to pull up a list of 12+" snowstorms at ANY of the airports (DCA, BWI, IAD, RIC) from 1970 to now. Apparently there was a 1 in 4.3 chance that you'd see a 12"er in a given season during then. So we are due, but apparently it's not astronomically rare—right now we're 1.66 standard deviations away from the mean, meaning there's about a 5-10% chance of a drought this long happening. For example, look at 1983-93 or 1993-2003.