Here are the stats for IAD (only goes back to 1962, so '58 and 61' would not be on this list):
1962 (Dec 26 - Jan 9, max 8")
1966 (Jan 27 - Feb 4, max 14")
1967 (Feb 7 - 11, max 10")
1969 (Dec 26 - 30, max 13")
1971 (Jan 1 - 5, max 15")
1978 (Jan 20 - 25, max 9")
1979 (Feb 13 - 23, max 22")
1982 (Jan 21 - 30, max 9")
1983 (Feb 11 - 18, max 22")
1984 (Jan 20 - 24, max 8")
1987 (Jan 23 - Feb 4, max 19")
1996 (Jan 7 - 18, max 24")
2003 (Feb 16 - 22, max 18")
2009 (Dec 19 - 25, max 18")
2010 (Feb 6 - 20, max 26")
2014 (Feb 13 - 18, max 8")
2016 (Jan 23 - Feb 2, max 28")
Notice that even tho we have longer gaps in these occurrences since the 80s, the max #s get gaudier.