I think that might have been an early season thing, I saw that there were areas of rain on the north shore early in the evening (like around 8 PM) while it was snowing to beat the band down here.
I wrote a post about the timing of the change to snow, tell me if you think this is fairly accurate- where does the UWS fit in here?:
9 AM Staten Island. 10 AM North Shore (Huntington/Oyster Bay) 11 AM Central Park 12 PM Brooklyn 1 PM Queens 1:30-2:30 PM Western Long Island