NWS ALY longterm, emphasis added
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
The New Year is set to start off quite active and volatile as a
major storm system, aided by two merging energies/waves (one from
the northern stream and the other from the southern stream), is
progged to impact a lot of real estate across the central and
eastern U.S. This storm system and merging waves are associated with
an amplified upper trough that will eject from the parent trough
over the western U.S. and shift eastward across the central and
eastern U.S. Potential impacts from all of this includes
accumulating snow/ice over the Midwest, Great Lakes, into the
Appalachians and Northeast U.S., and severe weather across the
southern U.S. New Year`s Weekend. This will be followed by a
major temperature swing New Year`s Weekend into the first week
of January across the eastern 2/3rds of the country as a potent,
modified Arctic cold front sends temperatures plummeting from
warmer than normal levels to colder than normal levels. This
remains the top headline during the extended forecast period.
Beyond New Year`s Weekend, parts of the local area (particularly the
SW Adirondacks, Schoharie, and Mohawk Valleys) could be impacted by
lake effect snow Monday into Tuesday, following the storm system.
There`s also some signals amongst forecast guidances that another
storm system could impact at least parts of the area later in the
week (Thursday-Friday time frame). Overall, the weather pattern will
remain progressive and temperatures are expected to run warmer than
normal levels in a southwest aloft flow regime.
Saturday night into Sunday, precipitation associated with the strong
mid-latitude cyclone, is expected to overspread our local area.
Strong ridging centered off the southeastern coast of the U.S. will
result in a return flow out of the southwest in the mid levels. This
will support increased moisture transport and warm air advection.
Given the setup, temperatures are expected to be warmer than normal
supportive of rain across most of the area (especially the river
valleys). A rain/snow mix eventually changing over to snow is
possible over the SW Adirondacks.
Sunday night into Monday, cold air from a potent Arctic cold front
will advect over the region. This will help in temperature profiles
cooling and snow levels dropping which will result in a change over
to snow over the valleys. However, forecast models are suggesting
that there will be limited moisture available so any snow should be
very light and brief over the valleys. There`s some signal,
primarily amongst the deterministic GFS, that indicates
frontogenesis/cyclogenesis taking place near the mid-Atlantic Coast.
Will have to continue to monitor these trends. For now, have stuck
with the NBM and kept that system removed from impacting the area
there fore keeping things rather dry on Monday across much of the
area.
Behind the storm system, cold westerly wind trajectories off the warm
Lake Ontario waters could result in lake effect snow over the SW
Dacks, possibly into the Mohawk and Schoharie valleys Monday into
Tuesday.
Dry and tranquil conditions over the entire are takes place on
Wednesday. Beyond Wednesday, we`ll have to see if another storm
system impacts the area later in the week.
Temperatures will remain mild during the extended period with
daytime highs in the 30s and 40s outside of Monday (20s/low 30s).
Overnight lows will be mostly in the 20s.