Taking the HECS chance off the table for now, let’s look at the last 3 super ninos. 82-83 wasn’t too bad actually, over 12” outside the Feb 83 HECS for Baltimore. 97-98 was obviously a shutout more or less. 15-16 was about 6” outside Jan 16 HECS. With this one being stronger than all of them and more east-based (for now, I’d wag it tends towards more basin wide as the winter progresses), I’d probably only put my Baltimore area forecast at 2-6” outside a HECS chance? But obviously the chance for a HECS is well above normal. I’d even go as far to say that the odds of a strong phasing low taking a traditionally favorable snow track for us is VERY high. 97-98 had like 3 of those! But will there be cold air? So I agree with @psuhoffman that when you put that together you get something like 1 in 3 odds maybe? So do you weight that and take 0.33x18” + 4” or something as your forecast total? Kinda no since I actually think a total like 8-14” for the year is less likely than either 2-6” or 18-24” lol. So to do a CWG kinda thing is probably wag:
0-2” 20%
2-6” 40%
6-14” 10%
14-24” 20%
24”+ 10%