He is just picking analogs of the top 3 historical storms that look like this current storm’s potential. When you blend those 3 analog storm totals, you get 10 to 15 at Harrisburg per his post this evening. One of his 3 analogs was PD2 back in February 2003. This storm as I mentioned a couple of days ago also reminds me a lot of that storm with the Arctic press meeting up with a strong moisture plume halfway across the country that delivered 20 inches to Harrisburg.