Tonight’s GFS data just became available. No major changes. The GFS QPF remains about 1.80 inches water and the snow ends early Saturday evening.
With these situations, averaging the NAM and GFS QPF values gives us 2 inches water falling as snow through early evening Saturday. A guess at 13-14 inches of snow for each inch of water will give us a range of 25-30 inches of snow for the immediate PHL area. Areas far north and west may get more if the NAM is correct. Drifting will make areas of snow seem deeper.
Let’s hope the power stays on. Now, it’s time to see what actually happens.
Tonight’s NAM model output shows the blizzard type system’s axis of heaviest snow banding setting up a bit further north of Philadelphia. Areas to the north and west of Philadelphia and in central NJ, previously thought to get lower snow totals, may in fact end up getting the greatest accumulating snows from this storm. The NAM joins the GFS in having the heaviest snow tapering early evening Saturday, with remaining light snow ending around midnight Saturday.
That said, the tonight’s NAM continues with a QPF of 2.20 inches water for grid point of PHL airport.
20-30 inches still likely with snow totals exceeding 30 inches if the tonight’s GFS model goes along with this increased QPF trend.
A bit of warming in the upper atmosphere about 7 AM may create some spectacularly heavy snow, but temperatures at critical vertical heights still support all snow, no sleet. Winds look to be 36 mph, satisfying meteorological definition of a blizzard.
The GFS data starts coming in about 10:30 pm. I’ll update around 11pm tonight.
