BOX AFD relative to this event:
Quite the interesting setup on Friday with a potent fast moving upper level disturbance crossing the region. The difficult part of this forecast revolves around marginal boundary layer temperatures coupled with a relatively narrow/brief swath of precipitation. We will discuss this more below. The 00z model guidance has really caught onto a potent shortwave and its associated cold pool aloft with 500T around -30C! As this strong shortwave/cold pool aloft approaches the forcing for ascent will rapidly increase. Precipitation will overspread the region from west to east Friday morning. While the boundary layer is marginal...model soundings coupled with strong forcing and dynamic cooling should allow Ptype to be mainly wet snow northwest of I-95. In fact...while short-lived an impressive band of 20+ units of omega in the DGZ is depicted. The cold pool aloft also generates steep mid level lapse rates and a -EPV signature, which would support a few hours of moderate to heavy snow convective type snow in a relatively narrow band. The question is where that band sets up, as the global guidance appears have this axis a bit further northwest than the high resolution models. Based on evaluating the data...feel the best chance for a few inches of snow will be northwest of I-95 into central and northeast MA. Even the low risk for localized 4-5" amounts depending on how this unfolds. Southeast of I-95, model soundings indicate boundary layer may be just warm enough to support rain or rain mixed with snow. However, intense omega could briefly overcome the warm boundary layer and flip ptype to wet snow as the heaviest precipitation crosses the region. There could also be a few inches of snow in the higher terrain of the Berks and maybe a coating to slushy inch or two in the Ct River Valley...but that will depend on the boundary layer temps. Later shifts may have to consider a Winter Weather Advisory depending on how the 12z guidance trends. Greatest risk for that right now appears to be northwest of I-95 with a focus on central and northeast MA, but that area may shift.