Thursday through Saturday...
Forecast confidence decreases beyond mid week but guidance is
beginning to come to a relatively consistent picture indicating not
one but two storm systems that will impact the region. The first
comes during the day Thursday, the second Friday and Friday night.
The biggest question is the exact track of these lows and what that
means with regard to precipitation type. Uncertainty is highlighted
by the great amount of spatial spread of the surface low tracks in
both global ensemble guidance sources, the EPS and GEFS. Even so, we
have a decent idea of generally what to expect. That being a
lighter, rain event on Thursday followed by a heavier precipitation
event on Friday which may very likely include some significant
freezing rain, especially in the interior of western MA. This is
because as Thursday's shallow mid level trough and sfc frontal
system pass by they are replaced by a sfc high pressure which acts
to pull in and hold sub freezing air in the low levels. This cold
air damming signature would keep <0C air at the sfc which warmer air
is lifted above on Friday setting up for a freezing rain situation
in those locations. So, while other less impactful outcomes remain
in the cards, there is potential for a significant ice event to
start the New Year. Beyond Saturday weak ridging and high pressure
should bring the return of quiet and seasonable weather.