In lower levels, models are starting to converge as NAM/ECMWF have
trended colder, albeit not quite as cold as GFS. Forecast soundings
show very favorable signal for a rapid transition from rain to sleet
(perhaps a brief period of freezing rain but that would be very
short lived). Note the warm nose aloft (+2 to 3C) and a deepening
near surface cold layer (-8 to -10C) up to 950 mb. Models also show
a good slug of QPF once the transition occurs, so this could be one
of those rare cases where sleet persists for several hours before
changing to snow as warm nose eventually cools. How fast this all
takes place is key as to how long it takes for sleet to change to
snow and obviously impacts accumulations of each.
At this point, we are becoming more confident that higher snow/sleet
accumulations will be north of Mass Pike, especially along and north
of Route 2 where 2-4" totals are possible. Totals should lower to 1-
3" along Mass Pike and 1" or less farther south, but keep in mind
these totals may need to be bumped up a little in subsequent
forecasts should colder trend continue on models. It`s also possible
that we see more sleet vs snow along and south of Mass Pike, perhaps
as much as 1-2" of sleet alone.
The combination of rapidly falling temperatures Friday could result
in a flash freeze and the transition to snow/sleet is expected to
result in hazardous travel. Since timing is centered around the
morning commute and into afternoon, and could have a significant
impact, we will issue a Winter Storm Watch for our northern CT,
northern RI, and all of our MA zones except south coast, Cape Cod,
and Islands (including the larger metro areas).
Note that icing from any freezing rain should be minimal (just a few
hundredths) and we do not expect any impacts from ice accretion
on trees or power lines.
