You'd be surprised at what 850's of -3 and -4 can deliver. If the ground temps are cold enough and you have a bit of elevation on your side, it could be an all snow affair.I don't know why but this one event has always been stuck in my mind. Can't remember exactly what year it was, possibly 2008-2009. I remember the Birmingham area got pasted with about 3-4 inches of snow on a Sunday evening and Leicester saw a mix of sleet/wet snow that didn't settle.
At the time, I was astonished because I was quite new to the models and at that time, I thought that snow wouldn't fall unless the 850's were -5 or lower. Well that evening, they were around -2! So if 3-4 inches can fall around Birmingham with those conditions, uppers of -4 aren't too worrying.
The good thing is, the PPN arrives at prime time for snow lovers, overnight! Always seems to be more marginal if it arrives during the day.