Albany, NY WFO Forecast Discussion

Forecast Discussion for ALY NWS Office
FXUS61 KALY 081203

National Weather Service Albany NY
703 AM EST Fri Dec 8 2023

A warm front will slowly lift northward today into Saturday,
bringing milder temperatures despite considerable cloudiness. A
strong cold front will bring a period of heavy rain and gusty
winds late Sunday into Sunday night, with rain possibly ending
as snow Monday morning as colder air surges into the region.


Cloud layer trapped by an inversion anchored by NW boundary
layer flow will persist much of the day over our region. Some
clearing in the mid Hudson Valley and NW CT that could remain
through at least this morning, with just a few high clouds
around. The boundary layer ridge axis is expected to shift east
of our region this afternoon, along with a boundary layer wind
shift to the west and southwest but winds will be weak.

The lower cloud layer should erode slowly from the west and
southwest through the day but temperatures should not be able to
rise much with the clouds and low sun angle not allowing for
much mixing. Highs in the upper 30s to around 40 with mid 30s
northern areas.


The amount of cloud erosion tonight is in question as
considerable high clouds are building into our region and the
boundary layer southwest winds are expected to be quite weak,
while surface winds should be south to south southeast, along
with lingering low level moisture. While some breaks in the
clouds are likely in some areas, clouds may again be slow to
exit in some areas, especially the Hudson River and points east.
Some patchy fog is also possible into early Saturday morning.

Then, if there are lingering clouds and patchy fog, with the
very weak southwest boundary layer winds and weak sun angle,
some areas may take quite a bit of time to clear out during the
day Saturday. There is a lot of uncertainty and quite a bit of
inconsistencies in sources of guidance/ensembles but favoring
the cooler side of guidance for highs Saturday. Highs in the mid
40s to near 50 with lower 40s higher terrain.

Amplifying upper trough begins its approach Saturday night and
strengthening warm advection, as well as boundary winds shifting
more south southwest and increasing, will help temperatures
warm on Sunday. However, increasing low level jet forcing,
moisture advection, upper dynamics proximate to the upper
impulse going negative tilt, and isentropic lift, will result
in rain spreading over our region through the day. The high
amplitude upper trough suggests moisture from the Gulf of Mexico
and Atlantic Ocean will result in anomalous moisture and the
very strong low level jet forcing will produce a widespread
heavy rain with potential localized flooding.

In addition to the heavy rain, winds will become gusty,
especially in higher terrain, where winds could gust over 40 mph
by Sunday afternoon. Some chances for even stronger winds but
how much mixing of the strong winds to the surface in the
heavier rain is in question. Highs Sunday in the mid to upper
50s with upper 40s to near 50 higher terrain.

Upper energy begins to exit and lift north and east Sunday night
as the leading edge of a tight boundary layer thermal gradient
and wind shift track through our region Sunday night. There are
still disagreements in guidance as to the timing of the onset of
the passage of the low level cold front, whether it is before
midnight or after midnight. Either way, cooling will be
occurring by daybreak Monday.

Some conditional instability and the strong low level forcing
suggests a line of shallow convection or narrow cold frontal
rain band, that could even have a rumble of thunder. Some
enhanced gusty winds and one last burst of heavy rain is
possible. Rain will change to snow in the southern Adirondacks
and perhaps parts of the eastern Catskills, with an inch or two
in the highest peaks by daybreak Monday.


Our main focus for the long term period will be on Monday when a
changeover to a period of heavy, wet snow is looking increasingly
likely on the backside of our impressive cold front from Sunday
night. Confidence is increasing for a secondary sfc low to not only
develop along the boundary Sunday night but for it to develop in the
equatorward entrance region of a north-to-south oriented 130-50kt
jet streak positioned on the leading edge of the parent trough. As
the parent trough tracks into the Northeast and trends from a
neutral to a slight negative tilt early Monday morning, strong upper
level divergence will likely occur, allowing the secondary low to
undergo cyclogenesis and deepen. Guidance now indicates it closes
off up to 700hPa by 18 UTC Monday as it tracks just to our
south/east and pushes into northern New England. This will allow
much colder air to quickly advect eastward as gusty sfc winds shift
to the northwest. As a result, thermal profiles crash by 12 - 18 UTC
Monday and with precipitation still occurring in the deformation
zone north/west of our exiting low, precip likely switches to heavy,
wet snow Monday morning. This unfortunately coincides with the
Monday morning commute so slippery travel conditions are looking
increasingly likely, especially for the higher terrain and hill
towns in eastern NY and western New England.

Wet-bulb zero heights drop down to about 500ft by 12 - 15 UTC so
elevations as low as 500ft will likely see some snow accumulations.
Even valley areas of the Greater Capital District could see a
changeover to wet snow Monday morning as temperatures and dew points
drop into the low to mid 30s. With such favorable dynamics in play,
forecast soundings also show high omega/lift intersecting the
dendritic snow growth zone (DGZ) so the hill towns in the
Helderbergs, Taconics, and foothills of the southern
Adirondacks/Catskills as well as the higher terrain will likely see
a period of moderate to even heavy snowfall rates. Thermal profiles
favor lower than climo snow to liquid ratios (SLRs) which will
likely yield a wetter/heavier type of snow instead of light/fluffy.
The probabilistic WSSI graphics (PWSSI) indicate that these higher
terrain and hill towns 1000ft in elevation and higher may experience
some snow loading issues given the weight of wet snow. Current PWSSI
highlight the southern Adirondacks in its 40 - 60% range for impacts
while the northern/eastern Catskills and southern Vermont range 20 -
30%. Helderbergs/Taconics and other hill towns are only in the 10-
20% range. Overall, snow amounts look light to moderate with WPC
Winter Storm Outlook showing the greatest probabilities for warning
level snow amounts (7" +) limited to the southern/western
Adirondacks. This is likely tied to the low SLRs and rather short
duration for heavy/wet snow confined mainly to late Sunday night
through midday Monday. Some snow loading issues from heavy/wet snow
will need to be monitored for these higher terrain areas.

To exasperate matters, west-northwest winds will be strong and gusty
throughout the day Monday with gusts reaching 30-40mph, potentially
higher in the higher terrain areas. Wind advisories may also be
needed. The strong winds and weight of heavy wet snow may
necessitate winter weather advisories or even isolated winter storm
warnings to help us message snow loading impacts for Monday, even if
exact snow amounts technically fall below warning criteria.

The rest of the week looks fairly quiet and seasonable with
potentially an Alberta Clipper dragging an arctic into the Northeast
mid-week. Depending on timing and the thermal/moisture gradient, the
front may lead to snow showers or even snow squalls but this is
still a low confidence forecast.


As of 12 UTC, MVFR ceilings are in place at ALB, GFL, and PSF
with low-end VFR visibility due to some patchy mist. Skies have
cleared at POU but mist has resulted in MVFR visibility. These
conditions should continue through 15 - 18 UTC but as cirrus
clouds continue to spill eastward this morning, low stratus
should erode and lead to VFR conditions. There is some
uncertainty regarding the exact timing for MVFR ceilings to
erode as an incoming warm front will remain to our south which
tends to keep low stratus around longer than we expect. For now,
we should VFR conditions arriving by 18 - 20 UTC but we would
not be surprised if low stratus continue longer, especially at

Assuming low stratus clear late this afternoon into this
evening, enough radiational cooling should ensue that low
stratus return by 03 - 06 UTC with even some fog possible. IFR
ceilings are evening and if they develop, should persist through
the end of the TAF period.

Light and variable winds expected through 00 UTC/09 before
south-southeast winds strengthen towards 5kts tonight.


Saturday Night: Low Operational Impact. Slight Chance of RA.
Sunday: High Operational Impact. Breezy. Definite RA.
Sunday Night: High Operational Impact. Windy With Gusts To 31 kts. Definite RA.
Monday: Moderate Operational Impact. Windy With Gusts To 31 kts. Likely RA...SN.
Monday Night: Moderate Operational Impact. Breezy. Chance of SHSN.
Tuesday: No Operational Impact. NO SIG WX.
Tuesday Night: No Operational Impact. NO SIG WX.
Wednesday: Low Operational Impact. Breezy. NO SIG WX.


A strong cold front is expected to move across the region
Sunday evening bringing a period of heavy rainfall to the area.
Total rainfall from Sunday afternoon into Monday morning will
range from 2 to 3 inches across the area. Locally higher amounts
cannot be ruled out across the higher terrain of the Catskills.

Some rivers could approach bankfull or even minor flood stage.
This is supported by latest river ensemble guidance from the
HEFS/NAEFS. If this threat materializes will depend on much
rain falls, how much snow can melt out of higher elevations, and
frozen versus non frozen ground. There could be some nuisance
urban and small stream flooding in low lying areas as well.

The latest WPC Day 4 Excessive Rainfall Outlook placed the
entire hydrologic service area within a marginal risk of
excessive rainfall. We will continue to carefully monitor





LONG TERM...Speciale

NWS ALY Office Area Forecast Discussion