Area Forecast Discussion
Issued by NWS Albany, NY

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000
FXUS61 KALY 130644
AFDALY

Area Forecast Discussion
National Weather Service Albany NY
144 AM EST Wed Dec 13 2017

.SYNOPSIS...
Low pressure will strengthen as it tracks northward through New
England tonight. Snow will continue across the higher terrain
of the Adirondacks and western New England and across lake
effect areas in the Mohawk Valley. As the low tracks into
northern New England and strengthens further, much colder air
will filter in with windy conditions developing on Wednesday.
Cold and brisk are expected Wednesday into Thursday, with a weak
clipper low bringing a chance of light snow to areas from the
Capital District southward late Wednesday night into Thursday.

&&

.NEAR TERM /THROUGH TODAY/...
Winter Storm Warning issued for Bennington county through
Wednesday morning for heavy snow.

Winter Storm Warning continues for southern Herkimer county for
heavy lake effect snow through Wednesday.

Winter Storm Warning continues through tonight for the western
Adirondacks, Glens Falls and Lake George Region, and western
Windham County in southern Vermont.

Winter Weather Advisory issued for Fulton, Montgomery, and
Schoharie counties for lake effect snow through Wednesday.

Winter Weather Advisory issued for southern Washington, eastern
Rensselaer, and northern Berkshire counties for snow.

Wind Advisory issued for the Mohawk and Schoharie Valleys,
eastern Catskills, Greater Capital District, northern and
central Taconics and Berkshires.

As of 1220 AM EST...As upper trough approaches, seems the
blocked flow regime was dissipating a bit across the central and
southern Taconics and southern portions of the Berks as drier
air was temporarily filling in...
HRRR/NAM3km support the idea of reducing PoPs/Snow a bit the
next few hours then redevelop with the passage of the upper
trough and a return to deeper moisture as lake effect influences
are increasing. As for Lake Effect, band was well developed
downwind of Lake Ontario as low level flow should begin to back
further taking the band southward across portions of the Mohawk
Valley and Schoharie Valley toward sunrise. So no changes to any
headlines at this time with minor adjustments based on
observational trends.

Prev Disc...
The synoptic snow event will transition into more
of a mesoscale event tonight into Wednesday, with upslope and
lake effect snow becoming the dominant features. The parent
surface cyclone is forecast to deepen considerably tonight into
Wednesday over northern Maine, while a broader closed
circulation develops at 700/500 mb over New England and colder
air pours into the region. Steering winds will shift to the
northwest as the system tracks northward through New England
tonight, with moisture up to at least 700 mb noted on forecast
soundings in the higher terrain north and east of Albany.

With regards to the warning upgrade for southern Herkimer
county, synoptic snow will quickly transition to lake effect
snow this evening. Current regional radar imagery already
indicating lake effect snow bands moving into central Herkimer
county as colder air aloft is quickly moving in from the west.
There is expected to be none or very little of a break in timing
from the synoptic to lake effect snow, so decided to upgrade to
a Winter Storm Warning with the potential for up to 7 or 8
inches in a few spots in southern Herkimer county from this
evening through Wednesday. A fairly steady state flow trajectory
around 290-300 degrees expected, so narrow lake effect snow
bands will oscillate across the same areas. Based on the strong
flow and fairly deep moisture through the night, some fragments
of bands will move across western Fulton, Montgomery and
Schoharie counties where 2-5 inches are possible in some spots.
The lake effect activity should weaken Wednesday afternoon as
inversion heights lower to around 850 mb.

In addition to the lake effect, upslope snows are expected to
develop across areas north and east of Albany. With a favorable
pattern setup, the 3km NAM and HRW-NMMB are also indicating this
potential. The Froude number forecast from the 4km BTV model is
less than 0.50 through Wednesday morning, indicating blocked
flow which should result in maximum upslope snow over Washington
and Bennington counties, and the northern Taconics, and
northern Berkshires. Will mention additional accumulations of
2-5 inches in these areas with up to 7 across the southern
Green mountains. Combined with heavy snow from earlier, had to
issue a Winter Storm Warning for Bennington county due to
continued moderate to heavy accumulations overnight. Storm
totals will be well over a foot at elevations above 1500 feet.

West-northwest winds will increase tonight as the system
deepens over New England. Strong winds will develop Wednesday
morning, as the pressure gradient increases substantially and
mixing heights rise to around 850 mb. Winds of around 45-50 kt
are forecast close to the mixing height, so some gusts up to 50
mph will be possible across favorable areas in W-NW flow such as
the Mohawk and Schoharie Valleys, eastern Catskills, Greater
Capital District, northern and central Taconics and Berkshires.
Wind speeds will decrease below advisory levels Wednesday
evening as mixing heights lower.

Other than the snowy and windy conditions, it will feel quite
cold and brisk across the entire region on Wednesday.
Temperatures will be around 10-20 degrees below normal for mid
December, with mainly teens in the higher terrain and lower to
mid 20s in most valley locations for highs. Combined with the
strong winds, wind chill values will be around zero to 10 below
zero in the mountains and single digits in the valleys.

&&

.SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/...
Lake effect and upslope snow should diminish by Wednesday
evening as the cyclone tracks well north into Canada. A weak
clipper low is forecast to quickly move across the lower Great
Lakes and northern mid Atlantic region Wednesday night into
early Thursday. The main surface cyclone will track south of our
region, but some of the ascent along the northern periphery of
the system could bring some light snow to areas from around
Albany southward. Models have been trending northward though, so
will have to continue to monitor. Only a dusting of
accumulation is expected at this time except a few tenths of an
inch for locations well south and east of Albany. It will remain
cold during this time, with single digits/teens for lows
Wednesday night and teens/20s for highs Thursday. The clipper
should quickly exit Thursday morning with dry conditions much of
the day.

Lake effect snow may start to re-develop Thursday night, as
west- northwest winds align with continued sufficient lake
induced instability. Main area of concern could be western
Mohawk Valley and into the western Adirondacks. Will continue to
monitor potential. Outside of lake effect, dry and cold
conditions will persist.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
Mean upper troughing over our region through the period with
chaotic broad cyclonic upper flow and little upper impulses
embedded within the flow. There are differences in guidance and
ensembles in the timing and track of these embedded impulses.
Each upper impulse will enhance lake effect snow bands into the
southern Adirondacks and western Mohawk Valley and at times
areas of scattered snow showers will break off and effect
eastern NY and western New England.

Tough to time specific time windows of enhanced snow shower
activity with small quick moving upper impulses but Friday night
into Saturday looks like one time period. Sunday night into
Monday is another potential time period and Monday night into
Tuesday is another.

The broad upper troughing in our region is expected to slowly
flatten as southern stream upper ridging ever so slightly builds
north. So temperatures moderate slowly Friday through Tuesday
so that by Monday and Tuesday, temperatures could be a slight
bit above normal, but still cold enough for mainly snow shower
activity with a mix of rain and snow showers in the Hudson
valley.

Highs Friday in the 20s with around 20 higher terrain. Highs
Saturday around 30 to the mid 30s but lower to mid 20s higher
terrain. Highs Sunday solidly in the 30s but upper 20s higher
terrain. Highs Monday and Tuesday in the upper 30s to around 40
but around 30 to mid 30s higher terrain.

&&

.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
Gusty west to northwest winds will continue to increase
throughout the morning with sustained winds up to 20 to 25 mph.
Gusts up to 40 mph are possible throughout the day as well.

Chances for snow showers will continue through the early
morning, mainly at KGFL/KPSF, but cannot rule out a stray snow
shower at KALB.

CIGS will generally be VFR but may drop to MVFR at times due to
a long fetch of moisture off the Great Lakes well east and
upslope into the Berkshires.

Outlook...

Wednesday Night: Low Operational Impact. Breezy NO SIG WX.
Thursday: No Operational Impact. NO SIG WX.
Thursday Night: No Operational Impact. NO SIG WX.
Friday: No Operational Impact. NO SIG WX.
Friday Night:  Slight Chance of SN.
Saturday: Low Operational Impact. Slight Chance of SN.
Saturday Night: No Operational Impact. NO SIG WX.
Sunday: Low Operational Impact. Slight Chance of SN.

&&

.HYDROLOGY...
No hydrologic problems are expected during the next week.

Cold weather with periods of snow and snow showers are forecast
much of the time. Any leftover light rain this afternoon will
change to snow showers this evening.

Ice will form and thicken on area lakes and rivers and some
river gauges may start to show erroneous readings due to ice by
the end of the 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...Wind Advisory from 7 AM this morning to 7 PM EST this evening
     for NYZ038>040-047>054-058-061-063-082.
     Winter Storm Warning until 7 AM EST this morning for NYZ032-
     033-042-043-083.
     Winter Weather Advisory until 6 PM EST this evening for NYZ039-
     040-047-082.
     Winter Weather Advisory until noon EST today for NYZ054-084.
     Winter Storm Warning until 6 PM EST this evening for NYZ038.
MA...Wind Advisory from 7 AM this morning to 7 PM EST this evening
     for MAZ001-025.
     Winter Weather Advisory until noon EST today for MAZ001.
VT...Winter Storm Warning until 7 AM EST this morning for VTZ014.
     Winter Storm Warning until noon EST today for VTZ013.

&&

$$
SYNOPSIS...JPV
NEAR TERM...BGM/NAS/JPV
SHORT TERM...JPV
LONG TERM...NAS
AVIATION...JVM
HYDROLOGY...JPV


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