DCA's ASOS is on the east (river) side of the runways. It is not near the buildings. Now, the snowfall measurement location is a completely different issue, but they seem to have fixed that in the past 5 years or so.
After driving down towards the river, I’m shocked that DCA did get on the board. There is no sign at all that it snowed, other than the cars that came in from higher elevations.
Iowa State. Utah state has the best download site for the full climate record for stations, but Iowa State's has the fun tools.
https://mesonet.agron.iastate.edu/plotting/auto/