AREA FORECAST DISCUSSION
National Weather Service Albany NY
920 AM EST Wed Nov 27 2024
.SYNOPSIS...
Largely dry and seasonable weather aside from snow showers in
the Adirondacks is expected today, however widespread rain and
snow will arrive tonight through Thanksgiving as a storm system
passes by to the south. Wet snow accumulations may be moderate
to heavy above 1000 feet elevation, with rain and some
accumulating snow at lower elevations. Cold and blustery
conditions are then expected through the weekend with impactful
lake-effect snow possible in the Adirondacks.
.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY NIGHT/...
Key Messages:
- Widespread precipitation expected Thanksgiving Day, with
moderate to heavy accumulations of wet snow favored in high
terrain. Lighter snow accumulations mixed with rain are
favored in valley areas where temperatures remain warmer.
- Precipitation type forecast remains sensitive to temperature
and precipitation rates, particularly in valley areas where
temperatures will be marginal for snow.
- Winter Storm Watches in effect 1 AM Thursday through 1 AM
Friday in the Mohawk Valley, eastern Catskills, Helderbergs,
and southern Vermont.
Discussion:
A progressive, positively-tilted shortwave trough will rapidly
traverse the region tonight through Thanksgiving Day, while an
associated surface low develops over the Ohio Valley before
deepening off the Mid-Atlantic coast and tracking toward the
Gulf of Maine. Recent high-resolution numerical guidance has
trended toward a deeper offshore low, as well as cooler
antecedent temperatures driven by rapidly increasing cloud cover
tonight, thereby limiting diurnal heating on Thanksgiving Day.
As such, the potential for moderate to heavy accumulations of
wet snow has increased at elevations above 1000 ft, while the
chances for accumulating valley snow have also increased.
Precipitation looks to spread from southwest to northeast in the
early morning hours on Thanksgiving Day, initially as snow.
After sunrise, temperatures will slowly warm, allowing some
transition to a rain/snow mix or entirely to rain for valley
locations, and particularly along and east of the Hudson where
easterly downslope winds will aid in pushing temperature above
freezing. As the surface low passes over southern New England
through Thursday afternoon, there is the potential for a band of
heavier snow rates to move across the region beneath a zone of
mid-level frontogenesis. HREF membership highlights areas from
the eastern Catskills into the central Mohawk Valley, as well as
possibly the Upper Hudson Valley into southern Vermont as most
likely to see enhanced snow rates through the afternoon, which
could result in rapid accumulations despite the marginal thermal
environment. A transition back to snow or rain/snow mix is
expected through the evening within cold advection as winds turn
westerly, while precipitation exits to the northeast overnight.
Gusts may reach 20-30 mph overnight in the Capital District as
well as in higher terrain of the eastern Catskills and western
New England as a colder airmass settles in.
There remains substantial uncertainty in valley precipitation
type through much of Thursday thanks to continued sensitivity to
both forecast temperatures and precipitation rates, with the
location of potential banding adding further uncertainty. At
this lead time, total liquid-equivalent precipitation of three
quarters to one inch is expected across much of the region,
with slightly lower values nearer half and inch in the southern
Adirondacks. Resultant snow accumulations of 7 inches or more
are most likely above 1000 ft elevation in the eastern
Catskills, Helderbergs, and southern Greens. The Mohawk Valley
may additionally see enhanced totals from potential banding.
Elsewhere, 1 to 4 inches of accumulation is expected, with the
lowest values across the Mid-Hudson Valley and lower elevations
of northwest Connecticut.
.LONG TERM /FRIDAY THROUGH TUESDAY/...
Key Messages:
- Lake-effect snow showers continue into the weekend, with several
inches of snow accumulation possible in the Adirondacks.
- Below normal temperatures expected to begin December.
Discussion:
With a large upper level trough settling in, a colder cyclone
W-NW flow regime will set up across the Great Lakes into the
Northeast from Friday through the rest of the long term period
early next week. Temperatures expected to be below normal during
this time. This pattern will be favorable for lake effect snow.
Precip chances will be modulated by short wave disturbances
passing through the mean broad upper level trough, which will
steer where lake effect snow bands will set up. At this time
there should be a more westerly flow trajectory Fri into Sat,
which would result in lake effect snow mainly across the W/SW
Adirondacks, with some possibly making it into the W Mohawk
valley at times.