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Area forecast discussion 
National Weather Service Albany New York
926 PM EST Fri Dec 2 2016

Synopsis...
a frontal passage and upper level trough will push through the
region tonight. A period of rain and snow showers, along with lake
effect, to impact portions of the region through tonight. A brisk
northwest flow with residual snow showers and flurries continue into
the start of the weekend with improving conditions expected
toward the second half of the weekend. Then a chance for light
snow increases Sunday night into Monday.

&&

Near term /through Saturday/...
lake effect band shifting south and losing some of its intensity.
Some scattered light rain showers are even extending into the
capital district, southern Vermont and the Berkshires. The intensity of
the precipitation is light enough that there is no mixing with
snow at this time. However, areas from the helderbergs and points
north and west are seeing some mixing and intervals of light snow
with a few embedded elements of higher intensity precipitation.

Based on these trends and mesoscale model output, some minor
adjustments to the rain/snow shower chances through the night and
all areas could see some snow flurry/shower activity before
daybreak as temperatures fall everywhere. Some adjustments to
temperatures a degree or two also. Previous afd has more details
on what is expected through Saturday and is below...

Upper trough and surface boundary was across Lake Ontario per
surface analysis and water vapor imagery. Regional radar shows an
enhancement to the activity where boundary layer temperatures were
still rather mild. However, New York mesonet web cams reveal where snow
was falling (near 1500 feet and higher) the accumulations have
been low at this time. Ground sensor temperatures at these mesonet
observations were still above freezing as well. However, this will
change tonight as the passage of these aforementioned troughs
usher in additional cold advection with boundary layer flow become
more northwesterly overnight. So per hrrr, seems a period of
moderate precipitation will push through most of the region this
evening along the boundary. Per thermal profiles and boundary
layer temps, a mix of rain/snow/graupal are all possible. Between
03-06z, the boundary layer flow becomes 300-320 degrees which will
take lake bands southward into portions of the Schoharie valley
and Catskills with moist cyclonic upslope conditions for portions
of the dacks into the southern greens and northern Taconics.
Additional accumulations in persistent lake bands should average
1-3 inches. As for cloud coverage, most areas should remain mostly
cloudy into this evening with some improvements for the capital
region down through the Mid Hudson valley and northwest CT as downsloping
should aid in additional breaks in the overcast. Overnight lows
average between 25 and 35 degrees.

Saturday a diminishing shower trend with a brisk northwest flow
regime as inversion heights lower a bit further. So mainly terrain
based shower activity under plenty of clouds across the terrain
and some mix for valley locations. Highs Saturday range from the
lower 30s across the terrain to lower 40s for valley locations.

&&

Short term /Saturday night through Monday/...
snow showers should tend to diminish Saturday night as the
pattern starts to become confluent aloft to a more anticyclonic
flow regime due to ridging to our west. Will mention just a
slight chance for snow showers west of the Hudson Valley early on.

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 New York with a lake
influence. Temps again look to be very close to normal for early
December.

Some discrepancies arrive Sunday night as overall synoptic
pattern favors the ridge axis sliding east overnight Sunday as
broad warm advection unfolds toward sunrise. Isentropic analysis
points toward isentropic lift with the European model (ecmwf) a bit more robust
than the NCEP model suite as cpd/S drop to less than 30mb. This
too would explain the higher quantitative precipitation forecast totals in the European model (ecmwf) than the
NAM/GFS with the ggem a bit more compromise. Per collaboration, we
will increase pops from southwest to northeast overnight into
early Monday morning. Then best lift and forcing tracks north of
i90 later Monday morning before the passage of the mid level
trough and wind field becoming west-northwest. Marginal lake
instability as h850 temps are expected to be around -6c and
upslope conditions may keep some rain/snow showers across the
terrain through Monday. Total snowfall accumulations generally
around 1 inch with up to 2 inches into the terrain of the dacks.

&&

Long term /Monday night through Friday/...
the extended period starts out dry...then things go downhill for
the middle and latter parts. High pressure ridging down through
Quebec and New England will give way to broad low pressure which
will cover most of Ontario province and the Great Lakes as of
early Wednesday.

Expect snow to overspread the forecast area Tuesday night...possibly
beginning as a mix early on across southern portions. The warm
front associated with this system may lift into the region Thursday
night but won't make much further progress before being overtaken by
the cold front during the day on Thursday.

Moisture wrapping around the intensifying low over southeast Quebec
Friday morning will keep showers going into Friday. It will also be
quite windy. With the westerly flow in place behind the low, the
moisture pattern will start to become lake-enhanced heading toward
the end of the week.

High temperatures Tuesday through Thursday will range mostly from
the lower 30as to lower 40s...but Friday will be colder with highs
from only the mid and upper 20s to upper 30s. Overnight lows will
be almost all below freezing...mostly mid and upper 20s. Tuesday
and Wednesday night...with Thursday night slightly colder.

&&

Aviation /03z Saturday through Wednesday/...
a weak surface and upper level trough will swing southeast across
the taf sites tonight. Rain and snow showers have already
developed and will continue to move east-southeast through the
area tonight. Brief periods of MVFR/IFR conditions will be
possible within any heavier showers but most locations should
generally see VFR conditions through the taf period.

Behind the trough, some lake effect/upslope snow showers may keep
MVFR conditions at kpsf periodically through tomorrow morning, and
may occasionally clip kalb. Kpsf could even dip into IFR at times.
Though, the most persistent activity should remain well west of
the taf sites.

West winds of 8-12 knots will likely continue to gust up to 20-25 knots
with the trough passage, especially at kalb/kpsf. Behind the
trough, winds will turn out of the northwest at similar speeds
through tomorrow afternoon.

Outlook...

Saturday night: no operational impact. No sig weather.
Sunday: no operational impact. No sig weather.
Sunday night: moderate operational impact. Chance of shsn...sn.
Monday: low operational impact. Slight chance of rain showers...shsn...sn.
Monday night: no operational impact. No sig weather.
Tuesday: low operational impact. Slight chance of rain...sn...sleet.
Tuesday night: moderate operational impact. Chance of rain...sn.
Wednesday: moderate operational impact. Chance of rain...sn.

&&

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.

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 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.
New York...none.
Massachusetts...none.
Vermont...none.

&&

$$
Synopsis...bgm
near term...bgm/NAS
short term...bgm/jpv
long term...wasula
aviation...jvm
hydrology...bgm/jpv

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