I've been meaning to add the RMM MJO index to that excel sheet on my website, I may do so while also updating all those indices.
Not a huge sample size but they're pretty evenly distributed across December in phase 7 from what I can see. I still haven't included every storm in this time period and normalized by # of days per month & MJO phase.
These are the storms have occurred in RMM phase 7 during December. What I find most interesting is that storms which produce any wintry precip in the piedmont and coastal plain are ice storms/CAD, and there are some big snows for the Apps and far western-northwestern piedmont. There's little-no snow SE of the Triad in any of these events.
December phase 7 RMM NC winter storms
December 25 1981 (NW piedmont + Mtns crush job)
December 8-9 1989 (Ice storm)
December 13-14 2000 (Ice storm)
December 4-5 2002 (Ice storm)
December 18-19 2009 (NW piedmont + Mtns crush job)
December 18 2010 (negligible)
December 8-9 2017 (NW piedmont + Mtns crush job)