Wednesday Afternoon Thoughts

You can click the map to get an idea of what I'm thinking as far as totals go.

Truth be told, I'm not sure what to think about this storm...this is a very, very unique situation. I have high confidence in the totals in Upstate NY and Northwest NJ/Northeast PA. I have medium confidence in New England and WV/MD/W PA, as well as DC/Baltimore. I have medium-low confidence in NJ/NYC/Philly/N Delaware.

Why?

A storm that tracks like this historically doesn't produce "heavy" (> 12") snowfall in Philly. Recall, last night I posted about some storms that were historically similar to this one, in some aspects. Here, once again, are those storms and their totals for Philly/NYC and the (jackpot):

Feb 14-17 1958: 13"/10.1" (Rochester: 30.6")
Dec 25-28, 1969: 5.2"/7.4" (Burlington, VT: 29.8"/Albany: 26.4"/Binghamton: 21.9")
Feb 18-20, 1972: 3.7"/6.3" (Binghamton: 24.4"/Syracuse: 20")
Jan 21-23, 1987: 8.8"/11.3" (Albany: 16.6")
Apr 18-19, 1983: 6"/1" (Scranton: 19.6"/Syracuse: 16"/Albany: 9")

The rough average looks like about 6" Philly and 8-10" NYC (somewhat ignoring the April 1983 storm due to sun angle/temperature differences). But notice, the interior got walloped. So historically, this doesn't have much support for a "big" storm near Philly...odds may be better near NYC, but given a number of factors, the odds are equal this time around I think.

That said, the models are doing the following for Philly/NYC:

GFS: 21.9"/1.4"
NAM: 6"/11.3"

Now, you tell me how confident you'd be in your forecast?

The GFS and NAM are usually a good duo to use this close into a storm. The NAM is generally too wet. The GFS can occasionally be too cold. A simple average doesn't work too bad usually at this point. However, when your difference are 10-14" between the models, taking a simple average is not a good idea.

So the bottom line?

- Major volatility is likely in Central NJ, South NJ, Philly, N Delaware and the NYC Metro area.

- Significant mixing with rain is possible all the way through the Hudson and Mohawk Valleys. This will limit snow totals here. In the Mohawk Valley, higher amounts are possible in higher terrain, and it's not out of the realm of possibility that someone on the valley floor ends up with less than 6", in my opinion. Same within the Hudson Valley. The Albany area will likely be extremely hindered by this.

- There may be a shadow effect in parts of Northeast PA or along the NY/PA border west of the Catskills, with downsloping off the Catskills drying out the air a bit and limiting snowfall (also noted this in the Champlain Valley and parts of Northern NY on the W side of the Adirondacks.

- Mixing is possible in the E Catskills as well, though elevation should take over and do work helping to keep totals elevated.

- There will be an extraordinarily sharp cut-off between snow and rain between Nassau County on Long Island and Essex County in NJ. Heavy snow becomes increasingly likely west of the Parkway.

- Potential for much higher amounts of snow (12-18") is possible north of the Atlantic City Expressway to New Brunswick, including Philly *IF* the cold air aloft comes in correctly and the precipitation sets up as shown on the GFS model. This could also extend further south into Delmarva as well. But again, historically, there is not precedence for this.

- DC/Baltimore...this isn't your storm. While some areas could pick up 4-6" of snow, most areas (especially further south near DC) will likely be shut out from much.