Area Forecast Discussion
Issued by NWS Albany, NY

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FXUS61 KALY 042108
AFDALY

AREA FORECAST DISCUSSION
National Weather Service Albany NY
408 PM EST Sat Dec 4 2021

.SYNOPSIS...
Lake effect snow showers will come to an end tonight into
Sunday for areas north and west of the Capital District. Sunday will
feature another quiet day with high pressure in control over the
area. A powerhouse storm system is expected to bring gusty winds and
periods of rain/snow showers to the area Monday into Monday night. A
coastal storm could impact eastern New York and western New England
by Wednesday. Temperatures will remain volatile through the middle
of next week averaging out slightly below normal levels. High
temperatures on Monday could top out in the mid 50s.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Lake effect snow showers are expected to come to an end tonight into
Sunday as a ~1030 hpa surface high pressure system builds into the
region. Total snowfall accumulations are expected to range between 1-
3 inches over the SW Adirondacks (Herkimer and Hamilton Counties). A
dusting is possible over parts of the Mohawk, higher elevations of
the Lake George/Saratoga area, and southern VT.

Cloud coverage will show some improvement tonight in response to the
high pressure building in. Skies are expected to be partly cloudy
over the valleys to mostly cloudy over the higher terrain of the SW
Adirondacks.

Overnight low temperatures will be near seasonable levels with
values in the mid to upper 20s most places and teens to lower 20s
over the higher elevations.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/...
Main weather takeaways Sunday through Tuesday:

* South-southwest winds will pick up late Sunday night into Monday.

* Precipitation moves into the area late Sunday night into Monday.
  Rain over the valleys; Rain/snow/ice transitioning over to rain
  over the higher terrain.

* Winds shift out of the west-northwest Monday evening remaining
  gusty just behind the frontal passage.

* At this point, winds look to remain just below advisory levels
  with gust as high as 35-40 mph through Monday evening.

* High temperatures ahead of the front on Monday could reach the mid
  50s along the river valleys.

Sunday will feature a period, albeit brief, of quiet weather with a
~1030 hpa surface high pressure system overhead. Skies should start
off as partly cloudy, but as the high quickly shifts east away from
our area, clouds will increase throughout the day on Sunday in
advance of a developing storm system over the northern Plains.
Additionally, winds will shift from out of the west to out of the
south during the course of the day. Day time highs are expected to
increase to near 40F degrees for the Capital Region, lower 40s mid-
Hudson Valley (upper 20s to mid 30s higher elevations).

Sunday night into Monday, this brewing storm system will shift
further east into the northern Great lakes/southern Canada.
Concurrently, the northern stream shortwave will begin to phase with
the southern stream shortwave. As this happens, the precipitation
and wind field of the low pressure system and northern stream trough
is expected to expand with its eastern edge getting into our west-
northwestern counties as early as Sunday night. P-types over the
higher terrain will favor snow, sleet, and/or freezing rain Sunday
night shifting over to all rain Monday amid further isentropic
lifting and warm air advection. Moisture associated with the
southern stream could result in some showers over our far
southeastern zones Sunday night into Monday. Winds will pick up out
of the southwest Sunday night.

During the day on Monday, the area will be placed in a zone of
increased cyclonic vorticity advection on the right entrance region
of an upper level jet. Integrated water vapor transport 1-2 STDEVs
above normal and PWATs 2-3 STDEVs above normal amid a 50-60+ low
level jet at 850 hpa will support periods of moderate to heavy
rainfall over the area. It will be breezy on Monday with southwest
winds 10-20 mph gusting as high as 35 mph (just below advisory
criteria). There could be some isolated areas that touch 40 mph.
This is large due to the placement/proximity of the sub 990 mb low
which will be well off to our north-northwest over Ontario/Quebec.
Given the amount warm air advection from the southwesterly winds,
temperatures will be unseasonably warm with values in the mid 50s
along the river valleys and 40s in the higher elevations.

Rain will transition over to snow following the passage of a sharp
cold front Monday evening/night. Most of the snow will be attributed
to lake enhancements and confined to our western and northwestern
zones. Total snow amounts will be on the order of 1-3 inches across
the higher terrain of the SW ADKs. Winds will shift out of the west-
northwest 10-20 mph remaining gusty post-frontal passage with gust
as high as 35 mph Monday evening. Westerly winds will weaken Monday
night into Tuesday.

On Tuesday, quiet weather returns under a colder and drier airmass
as high pressure builds in from the west. High temperatures on
Tuesday will be back to slightly unseasonably cool levels with
values in the mid to upper 30s along the valleys 20s to low 30s
higher elevations.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
Very active pattern through the long term, with initial broad
cyclonic mid/upper level flow across the northeast CONUS
transitioning to southwest flow by next weekend, due to potential
troughing digging across the western CONUS, and allowing for a
strengthening mid/upper level ridge across southeast CONUS.

An initial system associated with the broad cyclonic flow may bring
snow to the region Wednesday-Wednesday night, although there remains
uncertainty regarding progression of the main PV anomaly, with
12Z/04 GFS slower and allowing for greater surface low development
closer to the coast, while the ECMWF 12Z/04 ECMWF quicker, and
allowing for sfc development to occur farther east off the New
England coast. Thus, the GFS, with greater surface development
farther west, is implying a potentially more impactful winter
weather event for our region, with at least a large area of light to
moderate snow, while the ECMWF and GEM suggest a much lighter
snowfall event. Latest GEFs suggest the potential for light to
moderate snow, although greatest QPF is farther south/east than
operational GFS.

Based on this uncertainty, have sided very close to the NBM
guidance, which still suggests snow for much of the region Wednesday
into Wednesday evening, although intensity and amounts remain
uncertain. Will have to watch model trends for consistency over the
next 24 hours, and see if consensus continues to shift toward a
quicker/lighter snowfall event. There could be some mixing with rain
or perhaps frozen precipitation Wednesday afternoon/evening for some
valley areas, but these details remain highly uncertain at this time
range.

Another fast moving impulse may bring light snow or snow showers to
the region late Thursday night into Friday morning, with generally
dry conditions expected between systems for Thursday.

For Friday night into Saturday, warm advection takes hold in
response to aforementioned backing mid/upper level flow. Depending
on timing of individual impulses within this southwest flow, there
could be some periods of rain developing, especially
western/northern areas, which may be closer to passing upper level
impulses. P-type may include wintry mix across some sheltered areas
of the southern Adirondacks/southern VT, with mainly rain expected
elsewhere.

As for temperatures, sided close to the NBM, with generally below
normal temps through Thursday, then trending above normal by
Saturday. This yields highs mainly in the 20s and 30s through
Thursday, and 30s and 40s Friday into Saturday. Nighttime lows
mainly in the teens and 20s through Friday morning, with 20s and 30s
Friday night into Saturday morning, with the possibility of rising
temps in some areas during Friday night in response to clouds and
a developing warm advective regime.

&&

.AVIATION /21Z SATURDAY THROUGH THURSDAY/...
VFR conditions in place this afternoon as MVFR ceilings this morning
have improved to VFR ahead of an approaching cold front. Some snow
showers are possible this evening near GFL but any snow showers
should be isolated and brief. We introduced a TEMPO group to account
for possible brief MVFR ceilings from 21 UTC to 00 UTC. ALB, PSF and
POU should be far enough south and east to escape any snow showers.

After 03 UTC, ceilings should improve to VFR; however, as winds
shift to the west-northwest, enough of a fetch off Lake Ontario
should occur that MVFR ceilings may return to ALB and PSF. POU and
GFL should remain VFR. By 14 - 16 UTC, winds shift to the southwest
which should cut off the moisture fetch off the lake and allow
ceilings to improve to VFR.

South to southeast winds this afternoon will be sustained 8 to 15kts
before shifting to the west - northwest as the cold front moves
through the region mainly 00 - 03 UTC. As the winds shift, winds
should also strengthen with gusts up to 15 - 20kts possible.

Outlook...

Sunday Night: Moderate Operational Impact. Chance of RA...SN.
Monday: High Operational Impact. Breezy. Definite RA.
Monday Night: Moderate Operational Impact. Breezy. Chance of RA.
Tuesday: No Operational Impact. NO SIG WX.
Tuesday Night: Low Operational Impact. Slight Chance of SN.
Wednesday: High Operational Impact. Likely SN.
Wednesday Night: Moderate Operational Impact. Chance of SHSN...SN.
Thursday: No Operational Impact. NO SIG WX.

&&

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

A clipper low will bring light precipitation tonight with snow
the main p-type. Lake effect snow showers will end early Sunday
morning. Dry weather is expected Sunday. More widespread
precipitation is expected Monday with a strong cold frontal
passage, which could lead to some within bank rises on creeks
and small streams. However, widespread hydro issues are not
anticipated at this time.

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

Another storm system may impact the region with rain and/or snow
during the middle of the upcoming week, but precipitation
amounts and type remain somewhat uncertain at this time.

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...Evbuoma
NEAR TERM...Evbuoma
SHORT TERM...Evbuoma
LONG TERM...KL
AVIATION...Speciale
HYDROLOGY...Evbuoma/Main
EQUIPMENT...ALY Staff


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