Model guidance shifting north

There has been an overall trend northward in the last 24 hours. The NAM in particular, which previously grazed SNH, now delivers over 1" of liquid equivalent to the area. In fact all of southern and central New England see over 1" from the NAM. Keeping in mind the NAM frequently overdoes QPF, and considering other model guidance, might trim it back to over .75" for the region.

However, with the north trend also comes warmer temperatures, so there is increased concern for mixing. To start, we do not have any antecedent cold air in place, so all our cold air support comes from the high to the north and dynamics within the storm. While this should also restrict a significant ice event, a period of freezing rain (likely south of I90) could cause light accretion. Otherwise, a mainly snow event is still expected north of the NH/MA border, with periods of sleet mixed in. For Keene, temperatures will likely be isothermal through 850mb, with a small warm layer possible near 850mb, causing a mix with sleet.

Timeline:
Model guidance is still uncertain on the timing of the storm. The GFS remains on the fast side of the guidance, moving everything through by late Sunday. The NAM on the otherhand, doesnt bring precip in until midnight. The general consensus is that this will be a Sunday night event (helping to some extent with cold air issues), with snow ending late morning Monday.

Totals:
Still lots of uncertainty and potential for changes. The consensus on the track of the 850mb low is through PA and across LI, which places maximum snow accumulations over southern and central NH. Good storm dynamics and an isothermal temperature profile should help keep precipitation mostly in the form of snow, and give us good snow growth. Still, concerns for sleet keep the forecast down from its fullest potential.

Current snowfall forecast for Keene,NH (Sun-Mon): 4" to 7"