Area Forecast Discussion
Issued by NWS Albany, NY

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FXUS61 KALY 140549
AFDALY

Area Forecast Discussion
National Weather Service Albany NY
1249 AM EST Thu Dec 14 2017

.SYNOPSIS...
Cold and blustery conditions will continue through the
end of the week. Lake effect snow will diminish this evening, but a
clipper system is expected to bring some light snow to areas from
the Capital District southward late tonight. Another system will
bring the chance for mainly light snow Friday and Friday night, with
some heavier lake effect snow possible.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
As of 1230 AM EST...Regional and local radar scans show a slowly
column saturation as clipper system was racing across the Ohio
Valley. IR satellite image does reveal cooling cloud tops yet
dewpoint depressions remain quite high at this time. So
initially virga but the aforementioned column moistening up
should bring about some light snow around the I90 corridor and
points southward through the overnight period.

Prev Disc...
Overnight, the digging wave across the central Plains will
dampen out a bit as it rotates into the northeastern US, while a
reinforcing wave will be on its heels. The attendant surface
low will track west to east across PA and emerge into the New
York Bight by 12Z Thursday. The approach of this system will
disrupt the wind pattern over Lake Ontario, bringing an end to
the lake effect regime after 00Z. Forcing for ascent in the form
of isentropic lift and midlevel frontogenesis will spread into
southern portions of the forecast area after 06Z tonight. Model
cross sections and BUFKIT time/height sections indicate rather
weak ascent and paltry moisture. However, the ascent does
overlap the dendritic growth zone for a fairly deep layer, so
the snow that does manage to fall will likely see good ratios.
This forecast package has bumped up PoPs and snowfall
accumulations somewhat, mainly from the Mohawk Valley/Capital
District/Berkshires and points south. Model QPF fields still
support amounts generally an inch or less for most of this area,
with 1 to 2 inches possible for southern portions of our
Catskills/Mid-Hudson Valley/Northwest Connecticut zones, which
falls within WPC-generated ensemble guidance. Although
temperatures will bottom out from the negative single digits to
the upper teens, the apparent temperature may actually come up a
bit from current values in the negative single digits to teens
as winds diminish.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH FRIDAY NIGHT/...
The progressive nature of the clipper system should allow most
of the snowfall to end by or shortly after 12Z. Cold and dry air
advection will ensue for much of the day Thursday, although with
decreasing cloud cover we may actually see temps a couple
degrees warmer than Wednesday. It will be another blustery day,
although not quite as much as Wednesday, with westerly winds
gusting to 25 to 35 mph. Wind chills look to remain in the
negative single digits to upper teens for much of the region. A
west-northwesterly low-level flow would favor a lake effect
response, although there is a ton of dry air and inversion
heights are quite low, so do not have PoPs extending inland much
from the westernmost Mohawk Valley. Moisture and inversion
depths increase a bit overnight, so could see some light
accumulations over the Mohawk Valley. Another chilly night with
lows in the single digits and teens.

Friday and Friday night, additional midlevel energy will slide
across the forecast area downstream of a closed upper low. Some
weak isentropic lift ahead of this wave may result in some light
snow showers during the day for the Mohawk Valley/western
Adirondacks. Another chilly day with highs in the teens and 20s.
At night, a front will cross the region and allow for lake
effect activity to begin over favored areas of the
Adirondacks/Mohawk Valley, with a few snow showers possibly
spreading into the Schoharie Valley/Capital District/western New
England.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
Upper energy departs through the day Saturday as upper troughing
lifts north and flat upper ridging begins to build east from the
midwest and Great Lakes.  There could be a few leftover lake effect
snow showers but more sun than clouds likely with slowly moderating
temperatures.  Highs Saturday in the upper 20s to lower 30s but
lower 20s northern areas.

Sunday through Wednesday there are considerable differences in
sources of guidance and ensembles in the timing and track of upper
impulses within the chaotic northern stream upper flow.  Some
guidance has a strong system tracking through our region Monday and
Monday night with secondary weaker upper energy affecting our region
Tuesday and Wednesday. Other guidance shows more moderation through
the beginning of next week before a potential significant system
could affect our region more toward Tuesday and Wednesday.

Because of the fast chaotic upper flow and the high level of
uncertainty, not going to try to get too specific with timing of
enhanced chances of snow showers Sunday through Tuesday with some
possible mixed rain showers in southern areas Monday and Tuesday.
Wednesday is the most uncertain and confining any scattered snow
shower activity to western and northern areas if there is any lake
effect.  We will know more about next week as we get closer.

Highs Sunday in the lower to mid 30s but mid 20s higher terrain.
Highs Monday and Tuesday in the upper 30s to lower 40s but lower 30s
higher terrain.  Highs Wednesday in the lower to mid 30s but upper
20s higher terrain.

&&

.AVIATION /06Z THURSDAY THROUGH MONDAY/...
Mainly VFR conditions expected through this early overnight
period. CIGS will start to lower the next few hours as a
clipper low tracks eastward across OH/PA. Some light snow on
the northern periphery of this system will likely reach
KPOU/KPSF/KALB by 09Z, with mainly MVFR conditions. Will
mention IFR at KPOU since this terminal will be closer to the
track of the low pressure center. The light snow will end
between 13Z-15Z, with conditions improving to VFR thereafter.

Westerly winds less than 10 kt overnight. Winds become
northwest by around 14Z Thursday at around 10 Kt with gusts
around 20 Kt continuing through Thursday afternoon.

Outlook...

Thursday Night: No Operational Impact. NO SIG WX.
Friday: No Operational Impact. NO SIG WX.
Friday Night: Moderate Operational Impact. Chance of SHSN.
Saturday: Low Operational Impact. Isolated SHSN.
Saturday Night: No Operational Impact. NO SIG WX.
Sunday: Low Operational Impact. Isolated SHSN.
Sunday Night: Moderate Operational Impact. Scattered SHSN.
Monday: Low Operational Impact. Scattered SHRA...SHSN.

&&

.HYDROLOGY...
No hydrologic problems are expected through the weekend.

Temperatures will largely remain below freezing through the end
of the week and into the weekend, promoting ice formation on
areas lakes and streams. Periodic chances for light snow will
occur as well.

For details on specific area rivers and lakes, including
observed and forecast river stages and lake elevations, please
visit the Advanced Hydrologic Prediction Service /AHPS/ graphs
on our website.

&&

.ALY WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
MA...None.
VT...None.

&&

$$
SYNOPSIS...Thompson
NEAR TERM...BGM/NAS/Thompson
SHORT TERM...Thompson
LONG TERM...NAS
AVIATION...BGM/NAS
HYDROLOGY...Thompson



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