Precipitation type will become an issue starting early Saturday
night, perhaps even a bit sooner as shallow low level cold air
seeps southwestward down the Saint Lawrence Valley and into the
North country. This will bring a period of freezing rain to
Jefferson and Lewis counties, with the potential for up to a
quarter inch of ice accumulation, this will necessitate the
issuance of a Winter Weather Advisory for Jefferson and Lewis
counties starting Saturday night.
As colder air continues to seep in from the north, mixed
precipitation including freezing rain will gradually work south
through the area later Saturday night into early Sunday morning for
most areas south of Lake Ontario, perhaps not entirely reaching
the Southern Tier. The potential for some icing in these areas
will continue to be highlighted in the HWO product, but may
eventually need to add other portions of the area to the
advisory as the event draws closer.
Thermal profiles are cold enough Sunday, with 850 mb
temperatures rapidly dropping down to near -10C, to support all
snow. There may still be a period of mixed precipitation early
Sunday closer to the Pennsylvania line, but for the most part
Sunday looks to be a transition to all snow for everybody.
Snowfall amounts are only expected to be in the 1-3 inch range
although localized higher amounts are possible, especially over
higher terrain and areas where some lake enhancement occurs.
By late Sunday afternoon and certainly Sunday night...the cold air
will be deep enough to support a response off the lakes. Limiting
the lake snows though will be a general lack of synoptic moisture
and a cap that will lower from about 7500 ft. Regardless...a few
inches of lake snow can be expected southeast of both Lakes Erie and
Ontario. It will certainly be colder than recent nights...as the
mercury will drop into the teens over the western counties and will
tumble to the single digits across the North Country. Wind chill
values will be in the single digits for most areas...but will range
from 5 to 10 below for much of Jefferson and Lewis counties.