Albany Office Forecast Discussion

000
FXUS61 KALY 020909
AFDALY

AREA FORECAST DISCUSSION
National Weather Service Albany NY
409 AM EST Thu Dec 2 2021

.SYNOPSIS...
A warm front bring some light snow transitioning to rain
showers across the region this morning along with milder
temperatures today. A strong cold front will move through the region
tonight with scattered snow showers, blustery and cold conditions
for Friday. High pressure will bring fair and mainly dry conditions
for Friday night before another weak system brings snow showers and
flurries to open the weekend with seasonable temperatures.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
As of 408 AM EST...A warm front and mid-level short wave are
bringing a mixture of light snow and rain to the forecast area
this morning. The low and mid level warm advection has increased
with a southwesterly low-level jet of 35-50 knots at 850 hPa
moving over the region. The boundary layer has warmed enough for
a transition to rain in the mid Hudson Valley northward into
the Capital Region. However, enough low-level cold air was in
place for snow to break out to the north and west, as the strong
isentropic lift over spread the region. KGFL continues to have
some snowfall and some of the NYS Mesonet Cams in the Mohawk
Valley and the southern Adirondacks continue to have mainly
light snow depicted.

We are expecting 1-3" over the southern Adirondacks, portions
of the eastern Catskills and southern Greens. A half an inch to
two inches in the Mohawk River Valley, Lake George Saratoga
Region and Berkshires. A half inch or less elsewhere. Temps
will continue to rise above freezing this morning, and the pcpn
will transition to rainfall. As the lead impulse moves by, a
lull in the pcpn is possible based on the NAM and some of the
CAMS such as the HRRR. A little sleet may briefly mix in over
the northern zones.

Attention shifts to a vigorous northern stream disturbance
approaching from southeast Ontario and Georgian Bay. A
prefrontal trough will provide enough low-level convergence for
some scattered to numerous showers to move into the region in
the late morning into the afternoon. Ahead of the prefrontal
trough, and in the warm sector expect temps to rise above
normal. High temps will top out in the mid 40s to lower 50s in
the valley areas, and upper 30s to mid 40s over the elevated
terrain.

The cold front will be approaching for the night period as the
low level thermal gradient, and strong low-level FGEN occurs
with the boundary.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY/...
Tonight...A strong cold front moves across the region with
perhaps a narrow cold frontal rain band. Some of the CAMs like
the 3-km HRRR show a fine reflectivity lines with boundary
moving through between 6-10 pm. Others CAMs do not show it with
a frontal passage with some showers. Strong cold advection
occurs in the wake of the front. The 925 hPa winds increase to
30-40 kts. Some decent funneling will occur down the Mohawk
Valley. It will become blustery and cold with west to northwest
winds of 15-25 mph with gusts 30-40 mph. A quick lake connection
is likely with some west/northwest upslope snow showers. A few
inches of snow will be possible in the western Adirondacks and a
half an inch to a few inches of the southern Greens. The band
should be quick and transitory, as the flow veers quickly to
the northwest. Dustings to an inch or snow are possible in the
western Mohawk Valley, Schoharie Valley and Catskills. H850
temps tumbles slightly below normal based on the latest NAEFS
with actual values falling to -7C to -12C by daybreak. Lows will
be in the 20s to lower 30s with some teens possible in the
Adirondack Park.

Friday...The subsidence inversion lowers and ceases the lake
effect snow showers and flurries in the morning. The morning
begins blustery and cold with deeper mixing occurring. However,
a sfc anticyclone will build in for the afternoon with clearing
skies and diminishing winds. Expecting partly to mostly skies with
chilly conditions with those anomalously cold temps aloft.
Highs will be in the mid and upper 30s in the valleys, except
the mid Hudson Valley and southern Litchfield CTY where a few
lower 40s are possible. Mid 20s to lower 30s will be common over
the higher terrain.

Fri Night...Most of the time frame should be dry. The
deterministic guidance except for the NAM holds off the weak
isentropic lift with the next clipper type. Expect a shot of
radiational cooling early on before mid and high clouds race
in. Lows will be in the 20s to lower 30s with some teens over
the southern Dacks and southern Greens. Some weak synoptic
forcing with the warm front to the clipper may bring some light
snow or snow showers into locations north and west of the
Capital Region with very light snow accums.

Saturday...In the active quasi-zonal mid and upper level flow,
the clipper brings a round of snow showers or a mix of rain and
snow showers south of the Capital Region. Low-level moisture is
sparse, but light snow accums are possible over the southern
Adirondacks and northern zones. Highs will be near normal for
early December with upper 30s to lower 40s below 1000 feet in
elevation and mid 20s to mid 30s above it.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
Long term period will begin mainly dry for Sunday, but a strong
surface low and attendant cold front will bring widespread
precipitation to the area late Sunday night through Monday. We dry
out briefly Tuesday, but another storm system may affect the region
Wednesday or Thursday next week. More details below...

Long term period begins Saturday night with a weak surface low
quickly departing to the northeast and a surface high building into
the region from the west. With cold air advection and W/NW winds
behind this departing low, some lake effect snow is possible before
midnight for the Mohawk Valley. Otherwise, any lingering precip
should end early Saturday night thanks to rising heights aloft and
the surface high that will be overhead by morning. Guidance does
indicate some mid and high clouds beginning to stream in by Sunday
morning, which will prevent lows from dropping as far as they
otherwise might have. Even still, expecting 10s to 20s with some
single digits in the Adirondacks.

Sunday a potent upper-level northern stream trough looks to dig
southeastward across the central CONUS while a southern stream
disturbance tracks across Mississippi and Alabama. This northern
stream trough will induce surface cyclogenesis, and the resulting
surface low will track across the upper Midwest towards the Great
Lakes. We will also see rising heights aloft as the downstream ridge
amplifies over the East Coast. As a result, winds through the column
which will lead to warm air advection into our region for the second
half of the day. Therefore, expecting clouds to increase, but we
should remain mostly dry through the day. Highs will be in the 30s
for the high terrain and low-mid 40s for valley areas.

Sunday night...Northern and southern stream disturbances aloft begin
to phase over the Ohio River Valley and track eastward towards our
region. The mid-level warm front looks to move across our region
from south to north overnight, and with warm air advection
continuing and isentropic lift, we will likely see precipitation
increase in coverage, especially after midnight. While some snow may
initially mix in across the higher elevations of the Adirondacks and
southern Greens, precipitation looks to be plain rain for most
areas. Guidance has come into much better agreement of the track of
this system over the past few days. Sensitivity analysis developed
by Stony Brook University as part of CSTAR research shows that most
of the forecast uncertainty with this system lies in the amplitude
of the northern stream trough. This is correlated with uncertainty
in the strength of the surface low, but further analysis indicates
that there is less uncertainty (moderate confidence) in the storm
track and therefore the precip type. With abundant cloud cover and
warm air advection, only expecting overnight lows in the upper 20s
(ADKs) to mid 30s elsewhere, which is above NBM guidance.

Monday, phasing between the northern and souther stream disturbances
completes and the upper trough becomes negatively tilted as it
crosses our area. This will result in the surface low tracking well
to the north of our area, putting us in the warm sector. However,
widespread precipitation is expected, especially across the northern
2/3 of our cwa, ahead of the trailing cold front. An 50 kt low-level
jet at 850 mb (+2-3 sigma for this time of year)combined with strong
cyclonic vorticity advection and curvature to the flow aloft will
lead to plenty of forcing for ascent, so rain may become moderate at
times during the day Monday. A tightening pressure gradient will
also lead to winds becoming gusty out of the south ahead of the cold
front. Highs will likely reach the 40s in the Adirondacks with mid
50s in the Hudson Valley and Litchfield County, which is well above
normal for this time of year. However, temperatures will quickly
plunge behind the cold frontal passage during the afternoon and
evening...

...Behind the cold front, an impressive shot of cold air is expected
with 850 temperatures dropping to -10 to -12C by 12z Tuesday. The
surface low will continue to deepen as it pulls away from our region,
which will keep the pressure gradient tight, resulting in continued
gusty winds. With cold air advection and westerly winds over the
Great Lakes, some lake effect snow will be possible for western
areas, especially in Herkimer and Hamilton Counties. Advectively-
driven overnight lows will drop into the 10s to 20s.

Tuesday and Tuesday night should feature mainly tranquil weather.
The pressure gradient (and therefore winds) will decrease during the
day Tuesday as surface high pressure builds in from the south. As
winds decrease and the core of the cold air moves eastward, lake
effect snow showers will diminish. Highs will be in the 20s and 30s
Tuesday with overnight lows in the 10s and 20s.

Wednesday through Thursday...another storm system is possible, but
given expected convoluted upper-level flow pattern and long lead
time, forecast confidence remains low regarding this potential
system. While there is decent agreement amongst guidance that we will
see some precipitation during this period, the type and intensity
remain uncertain due to uncertainties in the track of any potential
storm and phasing between the northern and southern stream. Will
note, however, that there are some indications that any potential
storm could have a moisture source from the gulf of Mexico, so
another widespread precipitation event is possible. At this time,
will mention chance to likely PoPs Wednesday and Chance PoPs
Thursday with near-normal temperatures.

&&

.AVIATION /08Z THURSDAY THROUGH MONDAY/...
Through 06z/Fri...Rather complex forecast with multiple periods of
precipitation over the next 24 hours...Currently seeing VFR
conditions at all TAF sites as of 12:40 AM EST, but expecting
deteriorating conditions over the next couple hours as precipitation
pushes in from the southwest. Expecting ceilings to become MVFR at
all TAF sites after the onset of precip. At POU, looking at mainly
rain. At ALB and PSF, rain may initially mix with snow before
changing to all rain by around 9-10z. At GFL, expecting snow to
start changing to a rain/snow mix. Expecting MVFR visibilities
ranging from MVFR in rain to IFR in snow. Precip ends at all TAF
sites between 11-13z this morning. Snow accumulation will be less
that 0.5" at PSF and GFL and less than 0.1" at ALB and POU.

A lull in precip is expected until early afternoon. During this
lull, ceilings likely remain MVFR with improvement to VFR
visibilities. After 18-19z, another batch of precip moves in from
the west. This time, expecting mainly rain at all TAF sites.
Expecting reductions to MVFR visibilities. Ceilings will remain MVFr
with some IFR conditions possible in pockets of heavier rain. The
best chance is at GFL and PSF where have included prob30 groups to
reflect this possibility. Precip ends around 00z, with improvement
to VFR vsibilities and borderline MVFR/VFR ceilings, except at PSF
where ceilings may remain MVFR through the end of the TAF period.

Winds are currently light and mainly out of the south at all TAF
sites. Expecting southerly winds to increase to around 5 kts over
the next couple hours, and then to 5-10 kts by 12z. Winds remain at
around 8-12 kts mainly from the south through early afternoon. After
18z, winds remain southerly but some higher gusts to 20-25 kts will
be possible, especially at ALB and PSF. After around 00z, winds
switch to the west behind a frontal passage, but will remain breezy
at around 10 kts with some higher gusts possible at PSF through the
end of the TAF period.

Finally, vertical wind shear is expected at some TAF sites as a low-
level jet moves overhead early this morning through tomorrow
evening. Winds at 2000 ft are expected to be from the southwest at
around 35-40 kts. During the Thursday, winds at 2000 ft gradually
become more from the west/southwest through the day but remain at
around 35-40 kts before decreasing after 00z. Have included WS
groups in the TAFs to reflect this. Only reason WS was not included
for ALB is that surface winds are expected to be strong enough that
wind shear criteria will not be met. However, still expecting winds
at 2000 ft from the south/southwest becoming more southwesterly
through the day at around 35 kts at ALB as well.

Outlook...

Friday Night: Low Operational Impact. NO SIG WX.
Saturday: Low Operational Impact. Slight Chance of SHRA...SHSN.
Saturday Night: No Operational Impact. NO SIG WX.
Sunday: Low Operational Impact. NO SIG WX.
Sunday Night: High Operational Impact. Likely RA.
Monday: High Operational Impact. Breezy. Likely RA.

&&

.HYDROLOGY...
No significant hydrologic issues are anticipated in the ALY HSA
the next 7 days ending Wednesday.

While there may be some light precip in the form of snow and
rain over the next few days, most of this will be very light
and not impact the waterways. Temps briefly warm up above normal
today, but then drop below normal for Friday.  River and stream
levels will remain fairly steady into early next week.

Some ice will start to develop on some of the lakes, rivers and
reservoirs across the high terrain Friday into the weekend when
colder temps return.

A frontal boundary may bring a more widespread rainfall Monday
into Monday Night but the amount of QPF is still uncertain.

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.

&&

.EQUIPMENT...
The KENX radar will be down until mid December to refurbish and
replace the pedestal.

&&

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

&&

$$
SYNOPSIS...Wasula
NEAR TERM...Wasula
SHORT TERM...Wasula
LONG TERM...Main
AVIATION...Main
HYDROLOGY...NAS/Wasula
EQUIPMENT...ALY Staff

NWS ALY Office Area Forecast Discussion