CTP:
The operational GFS, ECMWF, and Canadian models continue to
show a similar story - isentropic ascent ahead of the storm
system moving into the region by Saturday morning and becoming
most vigorous by Sat afternoon into early Sat evening. By 00z
Sunday, the dominant forcing transitions from isentropic ascent
to fgen banding on the back side of the low, within a paired
right entrance / left exit region of the upper jet. This
scenario would result in several inches of snow across central
PA. However, it is worth noting that there are still some
ensemble members that keep most of the precip to the east,
resulting in little to no snow accumulation for central PA. The
range of possibilities shown by the NBM 10th and 90th
percentiles ranges from a coating to 1 inch in the best case to
over 1 foot of snow in some spots in the worst case scenario.
There will be a period of dry weather later Sunday through
Monday night before the next storm system approaches late Monday
night. This storm looks to be stronger than the weekend storm,
but also has the potential to track to our west, ultimately
putting is in the warm sector after a period of cold air
damming. In that case, there could be a several hour period of
snow before a mix with and changeover to rain. However, it is
much too early for details, as there is plenty of time for the
track of this system to change. The presence of cold air ahead
of this system will also depend and how much snowpack is left
behind from the weekend storm.
