748
FXUS61 KALY 230535
AFDALY

AREA FORECAST DISCUSSION
National Weather Service Albany NY
1235 AM EST Sat Nov 23 2024

.SYNOPSIS...
Low pressure developing off the New England coast will keep
unsettled conditions across the area through Saturday, with
rain and mountain snow showers overnight, gradually tapering off
on Saturday. It will become windy Saturday, with breezy
conditions continuing Sunday along with a mix of sun and clouds.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
.UPDATE...As of 1230 AM EST, have expired the Winter Storm
Warning for western Greene and Ulster counties as snow has
exited the region. We continue to monitor another band of mostly
rain rotating around the parent surface low over the Mid
Atlantic across portions of eastern NY and southern VT. Radar,
surface obs and webcams do show snow across southern VT mainly
at higher elevations near and above 1500 feet, with
accumulations mainly on grassy surfaces. Amounts of 1-3 inches
are possible over the next several hours.

This band will continue to drift to the south and west through
the morning, bringing additional rain and snow to much of
eastern NY, western MA and far southern VT. Additional snow
accumulations of one to two inches will be possible across
higher elevations of the eastern Catskills and Berkshires.
Previous discussion below...

[PREVIOUS 423 PM]...Our chilly and damp Friday continues as our
mature/occluded surface low meanders over the eastern Catskills
and gradually fills in/weakens. Now that the cold conveyor belt
has wrapped into the east side of the surface low, steady bands
of precipitation have developed up the Hudson River valley into
the southern Adirondacks. Despite marginal sfc temperatures in
valley areas, rain has transitioned to wet snow as precipitation
becomes steadier thanks to wet-bulbing processes. However,
accumulations are unlikely in valley areas given temperatures in
the mid-30s. Wet snow will accumulate in the elevations at and
above 1000 feet especially in the northern/eastern Catskills
through this evening with an additional 1 to 3 inches expected.
Additional power outages for these higher terrain areas are
possible given the wet snow weighing down on tree branches.
These higher elevations areas will drop into the upper 20s to
around freezing tonight so any wet and untreated surface tonight
can become slippery. Valley areas drop a few degrees into the
low to mid-30s but continued breezy winds should help mitigate
refreeze. Even still, patchy refreeze is not completely ruled
out where temperatures reach freezing.

Based on latest NYS mesonet obs and ground truth data, highest
snowfall totals have occurred in the eastern Catskills for
elevators around and above 1500 feet where reports range from 6
to 14 inches. Even western Albany County in elevations above
1000 feet have received 2 to 5 inches of wet snow with wet snow
showers evident on the NYS mesonet cameras. Use caution with
snow removal as the heavy, wet nature of the snow will make it
more difficult to shovel and clear.

Rain and higher elevation wet snow shower wind down this evening
before Midnight as the sfc low continues to weaken. However, a secondary
sfc low will rapidly develop off the New England Coast tonight as
a potent shortwave rotating around the parent cyclone becomes
negatively tilted and induces sfc cyclogenesis. There is good
agreement that an inverted/norlun trough develops on the west
side of the coastal low providing a focus for enhanced mid-
level FGEN resulting in a band of precipitation that extends
off the coastal low well inland. High res guidance suggests that
band including the HRRR reaches into southern VT around 03 - 06
UTC and continues through 12 UTC. While temperatures in valley
areas will likely be marginal enough to support plain rain, the
southern Greens, on the other hand, will be cool enough to
support wet snow accumulations, especially as diabatic cooling
processes cool the column down even further. Overall QPF amounts
look to range 0.10 - 0.30" and with marginal SLRs around 7-9:1,
total wet snow accumulations look to range 1 to 3 inches with
the highest amounts along the spine of the southern Greens. Some
light accumulations under 1 inch look to also accumulate in northern
Berkshire County mainly above 1500 ft.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/...
Heading into Saturday, our secondary coastal low will continue
to rapidly deepen as it tracks into the Gulf of Maine and towards
Nova Scotia. In fact, expected pressure falls suggest it may
even become a "bomb cyclone" as it deepens to around 975 hPa by
Saturday afternoon. The pressure gradient over the Northeast
tightens as this occurs resulting in strong gusty north to
northwest winds. In fact, cold air advection on the backside of
the low will help deepen boundary layer mixing and promote
efficient momentum transfer of strong winds down to the sfc.
Probabilistic guidance shows greater than 30 - 60% chance for
wind gusts to exceed 30mph through much of the day tomorrow
mainly for areas down the Mohawk Valley into the Capital
District and Taconics as well as the eastern/northern Catskills
and nearly all of western New England. Areas that still have
heavy wet snow weighing on tree branches may see renewed power
outages as the winds become gusty tomorrow. Otherwise, as
northerly winds shift to the northwest, wrap around moisture
supports upslope showers in the Taconics and southern Greens.
Froude numbers remaining below 1 through the day indicate
blocked flow with upslope showers remaining on the west side of
the Taconics and southern Greens. Marginal temperatures in the
mid to upper 30s warming into the low-40s will support initial
rain and leftover wet snow showers in the southern Greens
transitioning to mainly plain rain p-type.

As we lose daytime, winds shift to become more west-northwest
and will support enhanced cold air advection and as well as an
increased fetch off Lake Ontario. With Lake Ontario waters still
around 10-11C, the incoming air mass over the lake will surpass
the 13C difference criteria and likely will generate lake
effect showers that extend into the Mohawk Valley and northern
Catskills Saturday night. However, temperatures in the boundary
layer remain too marginal to support much in the way of snow,
especially in valley areas. In fact, a lack of moisture in the
mid-levels suggests cloud temperatures may be too mild to even
support ice nuclei. With sfc temperatures also only dropping
into the mid-30s, expecting mainly rain showers from lake effect
Saturday night. Otherwise, gusty northwest winds Saturday
evening gradually weakens overnight but winds remains breezy.

Lake effect rain showers diminishes Sunday morning but west to
northwest winds remain breezy with gusts up to 20-30kts. As
surface high pressure from the mid-Atlantic builds northward,
inversion heights fall and the lake effect response should end
leaving drying conditions for the afternoon. With some partial
breaks of sun, temperatures will turn a bit milder in the mid to
upper 40s. Partial clearing into Sunday night will allow
temperatures to cool into the upper 20s to around 30.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
After weeks of relatively tranquil weather, we are finally beginning
to settle into a more active pattern. In fact, Monday will likely be
the driest day of the extended forecast period with upper-level
ridging and surface high pressure building into the region in the
wake of upper-low that brought many areas their first measurable
precipitation in quite some time. High temperatures Monday will
reach the 40s and 50s with isolated pockets of upper 30s across
higher terrain before lows fall widely into the 30s Monday
night.

While at least the first half of the overnight period Monday looks
to remain dry, by early Tuesday morning, rain looks to begin to
spread into the region from southwest to northeast along and ahead
of a warm front associated with a parent surface low approaching
from the southeast Great Lakes. Within the warm sector of this next
system, much of eastern New York and western New England will see
rain as the predominant precipitation type, though some wet
snowflakes could mix in at higher elevations. High temperatures
Tuesday will be similar, though a few degrees warmer than Monday,
again primarily in the 40s and 50s. Rain continues Tuesday night
though gradually reduces in spatial spread as the surface low pulls
off to the north and east. By Wednesday morning, much of the
existing showers will be confined to the Southwest Adirondacks and
western Mohawk Valley as the result of lake effect influences driven
by the rotation of shortwave pulses through the southern periphery
of a closed low that will begin to take shape in southeast Canada.
With low temperatures Tuesday night falling into the mid/upper 20s
to low 30s, snow is likely to become the primary precipitation type
with these additional showers, though accumulations look light at
this time. With our region locked into cyclonic flow throughout the
day Wednesday, additional scattered showers will be possible before
the upper low overhead begins to pull away. High temperatures
Wednesday will primarily reach the mid/upper 30s across higher
elevations with low to upper 40s in valley areas, though pockets of
low 30s will be realized above 2000 ft. Therefore, showers that
persist through the day Wednesday could also produce some wet
snowflakes.

The remainder of the extended forecast period is rather uncertain as
significant differences exist within run-to-run guidance pertaining
to a potential storm system that could impact the region beginning
Thanksgiving Day and lasting through the end of the week. We will
continue to monitor this storm as lead time decreases, but at this
time there is not enough consistency to form a confident consensus
on what impacts, if any, will be had across the region.

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
Through 06z Sunday...Another surge of moisture wrapping back
around from east to west from has resulted in rain re-
developing, especially from KGFL-KALB and eventually spreading
south to KPSF after 08z. The rain should taper off from north to
south at KGFL- KALB by around 10z and KPSF by 12z. Most of the
steadier rain should stay north of KPOU, although scattered
-SHRA may occur there so added mention of PROB30 through 12z.
Conditions are primarily expected to be MVFR through 12z,
although occasional LIFR cigs may persist at KPOU for the next
1-2 hours. Also IFR cigs may develop at KPSF as winds become
more north/northwest resulting in upslope flow there.

After 12z, mainly scattered -SHRA expected into the rest of the
morning with MVFR cigs at KGFL/KPSF and mainly VFR at KALB/KPOU
although some brief periods of MVFR cannot be ruled out. Cigs should
trend towards VFR during the afternoon as drier air starts to work
in.

Winds will initially be northerly around 5-10 kt early this morning,
becoming northwest and increasing 15-20 kt with gusts of 25-35 kt
developing by this afternoon.

Outlook...

Saturday Night: Moderate Operational Impact. Windy. Chance of SHRA.
Sunday: Moderate Operational Impact. Windy. NO SIG WX.
Sunday Night: No Operational Impact. NO SIG WX.
Monday: No Operational Impact. NO SIG WX.
Monday Night: High Operational Impact. Likely SHRA.
Tuesday: High Operational Impact. Breezy. Likely SHRA.
Tuesday Night: Low Operational Impact. Breezy. Slight Chance of SHRA.
Wednesday: Low Operational Impact. Breezy. NO SIG WX.&&

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

&&

$$

SYNOPSIS...Speciale
NEAR TERM...Speck/Speciale
SHORT TERM...Main
LONG TERM...Gant
AVIATION...JPV