Area Forecast Discussion
Issued by NWS Albany, NY

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FXUS61 KALY 021736
AFDALY

Area Forecast Discussion
National Weather Service Albany NY
1236 PM EST Fri Dec 2 2016

.SYNOPSIS...
A trough of low pressure will move eastward from southern Quebec
through northern New England today into Saturday. A northwesterly
flow over the relatively warmer Great Lakes will continue to
result in lake effect rain and snow showers. Drier weather will
return on Sunday, as high pressure builds in across the region. A
weak disturbance will bring a chance of light snow late Sunday
night into Monday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
As of 1230 PM EST, Not much change from previous excellent
forecast. H2O vapor loop shows the approaching trough near the
north shores of Lake Ontario as lake effect/enhanced was
increasing per the KTYX radar. Plenty of cloud coverage with some
breaks into the valley locations and NW CT. Increasing gusty west
winds too will prevail as gradient remains a bit tight along with
good mixing and for a period of time some Mohawk enhancement
channeling.

Did raise temperatures a couple more degrees as pre-frontal
compression, increased mixing and some sunshine for valley
locations allowed for near 50F for valley locations.

Prev Disc...Lake effect precip will continue this afternoon due
to conditional lake induced instability and a fairly well aligned
W-NW flow across northern/central Herkimer and western Hamilton
counties, snow- liquid ratios will be much lower than typical lake
effect events. So it looks like around 1-3" additional snow for
this area today, with very little accumulation elsewhere due to
warm boundary layer temps.

Highest pops mentioned for the western Adirondacks and northern
parts of the Mohawk Valley late today, as rain/snow bands start to
shift south towards evening. Will also mention chance pops for the
southeast Adirondacks/Lake George area as well as southern VT due
to far inland extent with a multi-lake connection developing from
Georgian Bay and enough moisture for some upslope snow showers in
the southern Green mountains. Also chance pops for Schoharie
county and the eastern Catskills with some fractured bands of Lake
Erie potentially moving across this area.

Outside of lake effect, it will be mostly cloudy and breezy with
temperatures slightly above normal for early December. With the
approach of the aforementioned sfc trough from the northwest, west
winds are expected to increase this afternoon, and could become
quite gusty in close proximity to the Mohawk River/Capital Region
and Berkshires, where gusts could reach 25-35 mph at times.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY NIGHT/...
A short wave trough will pass through the region this evening,
allowing for lake enhanced rain/snow showers to possibly reach the
Capital District, northern/central Taconics and Berkshires this
evening. Valley locations will be mainly rain/snow mix while
higher terrain above 1000 ft will see snow showers with perhaps a
dusting to half inch in some spots.

The short wave passage will result in the mean mixed layer wind
direction shifting from around 290 degrees early in the evening to
around 320 degrees by daybreak Saturday. This will allow for lake
effect rain/snow bands to drift southward from the Mohawk Valley
southward through Schoharie county and eventually the eastern
Catskills. Inversion heights will be gradually lowering throughout
the night, which combined with the NW flow trajectory should
result in mainly light multi-band snow showers. Any snow
accumulations will be minor and generally confined to elevations
above 1000 ft, with an inch possible across the higher terrain of
southern Herkimer, Schoharie, western Greene/Ulster counties
tonight.

Saturday will feature continued cyclonic northwest flow, with
mostly cloudy skies and isolated to scattered lake effect/upslope
snow showers for areas west of the Hudson Valley. Flow trajectory
will continue to favor narrow multi-bands of light snow showers,
with inversion heights forecast around 800 mb. Temps will be very
close to normal for early December, with a northwest breeze making
it feel somewhat cool. Snow showers should tend to diminish
Saturday night as the pattern starts to become more anticyclonic
due to ridging to our west. Will mention just a slight chance for
snow showers west of the Hudson Valley.

Sunday looks to be a dry and seasonable day across the region
with high pressure moving overhead. Expecting partly to mostly
sunny skies, with more clouds closer to central NY with a lake
influence. Temps again look to be very close to normal. A
weakening upper level trough then approaches late Sunday night
with some light snow possible, mainly for areas west of the Hudson
Valley before daybreak Monday.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
The extended forecast features unsettled weather and quite a bit
of uncertainty as we head into the middle to latter portion of the
week.

Monday...A short-wave trough will be shearing out and
deamplifying over NY and New England based on the latest
ECMWF/GFS/Canadian GGEM and the WPC guidance. Some very light snow
or scattered snow showers are possible in the morning into the
early afternoon. High pressure will be building back in from
southeast Canada and the lower Great Lakes Region later in the
day. The synoptic forcing is weak with the shearing out trough, so
any snow accums will be light with a coating to a few tenths of an
inch. Highs on Monday will be in the upper 30s to lower 40s in the
valleys, and upper 20s to mid 30s over the hills and mountains.

Monday night...High pressure ridges back in over the Northeast
with clearing skies and cold conditions. With the sfc winds
potentially decoupling and near ideal radiational cooling
conditions, expect low temps falling back into the 20s with some
teens over the Adirondack Park.

Tuesday...Another system approaches from the Midwest and the Ohio
Valley. Much of the day should be dry with increasing clouds that
will be thickening and lowering from southwest to northeast. Some
over running light snowfall is possible very late in the afternoon
well south and west of the Capital Region, as low pressure moves
over OH and the warm front reaches PA and the mid Atlantic Region.
Highs will be mainly in the 30s with a few lower 40s in the mid-
Hudson Valley and upper 20s over the southern Adirondacks and
southern Green Mountains.

Tuesday night...The storm system runs into ridging over southeast
Canada and the Northeast and begins to weaken and deamplify again.
We leaned closer to the GFS and the superblend of the guidance
with a primary low moving into the eastern Great Lakes with a weak
secondary low off the NJ coast. In the southwest low and mid level
flow over NY and New England this system will likely produce some
light snow with some isentropic lift ahead of the warm front to
the primary system. The better QG lift is west of the Hudson River
Valley. Some light snow accums of a few inches are possible
especially west of the Hudson River Valley. The latest GFS
critical partial thicknesses favor snow with perhaps a mix to some
light rain over the valley areas towards daybreak. Lows will be in
the mid and upper 20s, and temps may rise after midnight.

Wednesday into Thursday...There is where the forecast becomes
uncertain with the timing of the next few systems. The ECMWF would
have the system weaken WED morning with high pressure building
back WED late pm into the early evening. A low pressure system
near the cntrl MS River Valley would be rounding the base of a
positively tilted upper trough and move towards the eastern Great
Region and Northeast for THU. The GFS lingers the WED morning
system over NY and New England, and ejects another wave along the
eastern fringe of the upper trough quicker WED night into THU with
the primary low over western NY by 12Z THU. If the wave moves this
far west, then this would be a warm solution with some snow to
rain /possibly even some sleet or freezing rain/ late WED night
into THU. WPC guidance is a little closer to the GFS with a triple
point low forming THU morning over Lake Erie. Our forecast starts
with a light rain and snow mix WED morning into to predominately
rain in the afternoon when the boundary layer warms. Some cooling
Wed night would favor a chc of snow at most location early.
However with a strengthening of the southwest flow in the low to
mid levels, and the track of the primary low well west of the
Hudson River Valley, this favors a transition to rain on THU with
chc pops. Once the front moves through THU night, a quick
transition to some wet snow is possible. The evolution, timing and
details of this system are at the low confidence level at this
point, as the Global ensembles are showing quite a bit of spread
too. Temps continue at seasonable levels for early DEC WED to THU.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
A weak surface and upper level trough will swing southeast across
the TAF sites this evening. Rain and snow showers will immediately
precede and accompany its passage. Some lake effect snow
showers/flurries may impact KPSF and perhaps KALB at times later
tonight into Saturday morning, although the most persistent
activity should remain well west of the TAF sites.

Generally VFR conditions are expected through this afternoon.
Then, as the aforementioned trough approaches, showers of rain,
then snow are expected to develop at KGFL/KALB and KPSF between
roughly 23Z/Fri-05Z/Sat. Brief periods of MVFR/IFR conditions will
be possible within any heavier showers.

Behind the trough, lake effect/upslope snow showers may keep MVFR
conditions at KPSF periodically through Saturday morning, and may
occasionally clip KALB. KPSF could even dip into IFR at times.
Elsewhere, mainly VFR conditions are expected through Saturday
morning.

West winds will increase to 8-12 KT this afternoon, with some
gusts of 20-25 KT possible, especially at KALB/KPSF. West winds
will veer into the west/northwest behind the trough at similar
speeds tonight into Saturday. Some briefly stronger wind gusts up
to 30 KT could occur immediately ahead of, and with the trough
passage this evening.

Outlook...

Saturday: Low Operational Impact. Slight Chance of SHRA...SHSN.
Saturday Night: No Operational Impact. NO SIG WX.
Sunday: No Operational Impact. NO SIG WX.
Sunday Night: Low Operational Impact. Slight Chance of SN.
Monday: Low Operational Impact. Slight Chance of SHRA...SHSN.
Monday Night: No Operational Impact. NO SIG WX.
Tuesday: Low Operational Impact. Slight Chance of RA.

&&

.HYDROLOGY...
Rainfall over the past couple of days resulted in some modest
within- bank rises on area rivers (especially south and east of
Albany... please refer to the public information statement
released earlier for storm total rainfall). River levels will
continue to slowly recede through the next several days.

Today through Saturday there will be periods of lake
effect/upslope rain/snow showers. Snow will be likely at higher
elevations with a mix of rain/snow showers in the valleys. The
precipitation will be heaviest in the western Adirondacks where it
will fall mostly as snow. The precipitation from today through
Saturday will have little impact on rivers and streams.

Some light snow is possible Sunday night into early Monday, with
better chances for wintry precip towards the middle of next week.

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...JPV
NEAR TERM...KL/BGM/JPV
SHORT TERM...JPV
LONG TERM...Wasula
AVIATION...KL/Wasula
FIRE WEATHER...
HYDROLOGY...BGM/JPV



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