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fxus61 kaly 110550 
afdaly

Area forecast discussion
National Weather Service Albany New York
1250 am EST Mon Dec 11 2017

Synopsis...
lake effect snow will impact portions of the western
Adirondacks tonight. Fair weather is expected for Monday with a
widespread snowfall expected for Monday night and Tuesday as
another storm system approaches from the west.

&&

Near term /until 6 am this morning/...
as of 1245 am EST...Winter Weather Advisory for lake effect
snow remains in effect tonight for northern Herkimer and western
Hamilton counties.

Lake effect snow has shown a resurgence this evening thanks to
the combination of steep low level lapse rates and upper level
wave progressing through which is likely helping with seeder-
feeder processes. So lake band will persist through the rest of
the overnight and per the rap/hrrr, we will see this band slowly
drift south around sunrise. Rest of the region, outside of
flurry, variable cloud coverage.

Prev disc...
broad upper level through continue to be situated over the Great
Lakes and northeast US. With W-SW flow coming parallel over the
long axis of Lake Ontario, a single concentrated band of lake
effect snow is occurring off the eastern end of Lake Ontario.
Although the heaviest of the band has been occurring across the
Watertown area and over the Tug Hill, some moderate snowfall has
been occurring in the Old Forge area. Several new inches of
snowfall has occurred today in Old Forge according to the New York state
mesonet station and web cam imagery.

Over the next few hours, the band will continue to slowly drift
across the western Adirondacks. Eventually, it will start to
shift southward and weaken by the late night hours, as the low-
level flow starts to shift in response to a frontal boundary
swinging through the area. Before that occurs, a few more inches
of snow accumulation is likely, especially along the Route 28
corridor around Old Forge and inlet.

Elsewhere, skies are mostly cloudy. Cannot totally rule out a
few upslope snow showers or flurries across southern Vermont and in
western areas thanks to the approaching frontal boundary, but
much of the area will remain dry and quiet through the overnight
hours.

Temperatures will be near normal overnight with teens higher
elevations to 20s lower elsewhere.

&&

Short term /6 am this morning through Wednesday/...
... Storm watch posted for northern half of forecast
area...

Weak high pressure will build in for Monday. There could be
some light snow showers across the northwest portion of the area
as a weak cold front settles south. Otherwise, expect some
sunshine particularly in the afternoon. Temperatures will be a
few degrees below normal.

Clouds will increase later Monday into Monday night ahead of the
next storm system. Models are in good agreement that low
pressure will track across into the northern portion of the
forecast area on Tuesday. Secondary development will occur off
the Long Island coast with the primary low tracking into Maine.
NAM and GFS in good agreement on quantitative precipitation forecast with upwards of 0.75 inch
total forecast in the Max zone running along a Herkimer-Fulton-
Saratoga- Windham line. The Euro comes in somewhat lighter in
this region. Ascent from this storm looks to be driven by warm
advection with particularly impressive Omega noted on the
280k/285k surfaces. Other parameters such as dendritic growth
zone and fgen forcing are not overly impressive. That being
said, the isentropic lift is supportive of the quantitative precipitation forecast totals.
Recent research here at the office has focused on using our gis
tool gazpacho to offer guidance on quantitative precipitation forecast biased forecasting in
various flow regimes. For the upcoming storm, we are looking at
925mb winds southeast around 30 knots. Research shows that in
this regime we have typically underestimated snowfall in favored
upslope regions of the Adirondacks and greens. Putting it all
together we are looking for 8 to 12 inches in the watch area
with amounts trending lower away from watch zones. This would
imply advisory criteria snowfall for much of the remainder of
the area. Across the Mid Hudson valley temperatures may warm
enough to bring some rain into the picture holding down totals.
High temperatures will range from mid 20s north to upper 30s
south.

In the wake of the system cold and blustery conditions set in
for Tuesday night and Wednesday. Lows on Tuesday night are in
the single digits to mid 20s. Highs on Wednesday will barely
budge from morning lows. These temperatures combined with gusty
winds of 15 to 25 mph will yield wind chill values from minus
10 degrees to the teens.

&&

Long term /Wednesday night through Sunday/...
our active and wintry pattern continues into the extend forecast as
a longwave trough persist over the eastern conus. While we will be
monitoring numerous shortwave rotating into the northeast which will
present a number of snow threats, model agreement remains poor on
exact timing, placement and intensity of each shortwave. However, we
have higher confidence in a period of below normal temperatures
impacting eastern New York/western New England Thursday - Friday.

We start off the extended Wednesday night with the potent, closed
upper level trough responsible for the snow event Tuesday positioned
east of our area. Northwest flow behind this trough should lead to
cold air advection and the start of cold temperatures in our region.
H850 isotherms fall to -15c to 18c and low temperatures are expected
to fall into the teens in the valley and single digits elsewhere.
Such cold air flowing over the relatively warm lakes could lead to
continued lake effect snow, especially in the Adirondacks and Mohawk
Valley.

High pressure tries to nose in from Canada during the day Thursday
and the change in flow regime plus subsidence should suppress the
lake effect snow bands. The incoming high could lead to a slight
pressure gradient leading to somewhat breezy winds. Thus, wind
chills Wed night into Thursday could fall below zero, especially in
the hill towns/elevations. Wind chills in the Adirondacks could even
fall into the negative teens so we'll be keeping a close eye if any
Wind Chill Advisory headlines will be needed.

Chilly temperatures remain in placement Thursday - Friday with high
temperatures likely only rising into the 20s and lows in the
teens/single digits which is about 10 - 15 degrees below normal for
mid - December. Our next shortwave exits the Great Lakes and heads
into our area bringing the next threat for snow Friday - Saturday.
While some moisture is associated with this disturbance, poor model
agreement remains on placement, timing and intensity giving US a low
confidence forecast on snow potential. However, we increased pops to
slight chance and even chance to reflect this threat.

Height rising are possible in the wake of this trough leading to the
flow regime shifting to west or even SW with temperatures rebounding
closer to normal heading into the weekend. However, additional
shortwaves are expected to traverse the northeast late in the
weekend into early next week which will once again bring additional
threats for snow. Moisture look lackluster at this time so any
threats should be of the lighter variety.

&&

Aviation /06z Monday through Friday/...
VFR conditions are expected the remainder of the overnight and
into the day on Monday. With an upper level trough overhead and
lake-effect snow upstream of the area, there will continue to
bkn-ovc cigs around 4-9 kft, esp for kgfl/kalb. Otherwise,
light and variable winds or S-SW winds of around 5 kts is
expected through the overnight hours with no precipitation
expected.

Daylight hours on Monday, there will be sct-bkn cigs around 4-6
kft with no precip through the day. Westerly winds will be
around 10 kts. Some mid level clouds may increase towards
evening as the next storm system approaches from the west.
Chance of snow appears to be after this taf forecast cycle.

Outlook...

Monday night: high operational impact. Definite snow.
Tuesday: high operational impact. Definite snow.
Tuesday night: low operational impact. Slight chance of shsn.
Wednesday: moderate operational impact. Breezy chance of shsn.
Wednesday night: no operational impact. No sig weather.
Thursday: no operational impact. No sig weather.
Thursday night: low operational impact. Slight chance of shsn.
Friday: moderate operational impact. Chance of shsn.

&&

Hydrology...
no hydrologic problems are expected through the week ahead.

Cold weather with periods of snow and snow showers are forecast.
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.
New York...Winter Storm Watch from late tonight through late Tuesday
night for nyz032-033-038-039-041>043-050-082>084.
Winter Weather Advisory until 7 am EST this morning for nyz032-
033.
Massachusetts...none.
Vermont...Winter Storm Watch from late tonight through late Tuesday
night for vtz013>015.

&&

$$
Synopsis...okeefe
near term...frugis/bgm/okeefe

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