For what it's worth I went back and read some on the 1958 storm. D.C. was just above 4" while nw had over a foot.
Correction: D.C. was just under 5" and BWI had 8.4".
I'm very interested in the correlation PSU showed. That was one of the best pattern correlations I've seen! There's no way we miss out! Too bad we can't see how well computer models would have done leading up to the 1950s and 1960s March storms.