Area Forecast Discussion
Issued by NWS Albany, NY

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FXUS61 KALY 060013
AFDALY

Area Forecast Discussion
National Weather Service Albany NY
713 PM EST Mon Dec 5 2016

.SYNOPSIS...
Light snow downwind of Lake Ontario will begin to diminish during
the evening. High pressure will start to build tonight into
Tuesday. Another burst of light snow will begin Tuesday night and
end Wednesday afternoon. Snow showers and lake effect snow will
produce additional accumulations toward the end of this week.

&&

.NEAR TERM /THROUGH TUESDAY/...
As of 700 PM EST...Weak Lake Ontario response continues as lake
effect rain/snow was impacting portions of the central part of the
forecast area. As 1020mb surface high builds in from the Ohio
Valley tonight, this should further diminish the lake effect as
we will drop back PoPs quickly through the late evening hours.
Otherwise, challenge will be the cloud coverage overnight. Valley
locations should see more breaks than the terrain through the
evening hours then additional breaks occurring overnight. As winds
diminish to less than 5 kts, this should allow for temperatures to
drop back into the 20s.

High pressure transverses the region through Tuesday with at least
some sunshine before becoming filtered with increasing high and
mid level clouds. The NAM is quite aggressive when compared to the
GFS/ECMWF as an enhanced FGEN band lifts into the Catskills and
Mid Hudson Valley by late afternoon. Per collaboration and
ensemble members, we will slow down the onset of precipitation.
This too agrees with the isentropic analysis where the best lift
and lowering cpd/s remain upstream and low level ageostrophic flow
remains from the northerly direction which should keep the drier
air in place a bit longer. Highs range from the low-mid 30s to
lower 40s.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
Another period of light snow expected Tuesday night into Wednesday
morning.

Similar to the event this past Sunday night into Monday morning,
broad isentropic lift increases ahead of approaching short wave
and negatively tilted trough axis for light precipitation to
overspread most of the region Tuesday night. Forecast profiles
point toward mainly snow, yet some rain could mix in toward the
I84 corridor as wet bulb profiles are expected to be just above
freezing. QPF forecasts are rather light as another 1-3" of snow
seems likely at this time. A drop cut off in the precipitation is
expected from west to east Wednesday morning as a narrow
anticyclonic flow regime quickly sets up Wednesday afternoon into
Wednesday night. As a brisk and relatively moist southwest flow
regime sets up in the mid and upper levels, there will likely be
considerable opaque cloud coverage across the region.

Highs Wednesday from the mid 30s to mid 40s and overnight lows
Tuesday night range between 25-35F and Wednesday night lows mainly
into the 20s.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
The period starts out on Thursday with a short wave trough and
surface cold front moving across the area with some snow showers.
Temps aloft more than cold enough to produce a lake response, so
with a westerly flow regime lake effect snow bands will likely
develop downwind of Lake Ontario and start to affect the western
Adirondacks with some accumulation expected. Confidence fairly high
even this far out, so will mention likely to categorical pops for
much of northern Herkimer and Hamilton counties Thursday with
mainly chance pops outside the lake effect areas.

A re-enforcing short wave and cold front is forecast to move through
Thursday night, which will shift the flow trajectory to more of a
northwest direction late Thursday night. This will send lake effect
snow bands southward into the southwest Adirondacks, western Mohawk
Valley, and Schoharie county by Friday morning. Additional snow
accumulations from lake effect will occur in these locations.
Depending on when the wind shifts will have impacts on eventual snow
accumulations. As the flow further veers on Friday, narrow multi-
bands are expected across the higher terrain west of the Hudson
Valley with brisk conditions developing across the region.

The coldest air thus far of the season will be ushered in from
Friday through Sunday, with temperatures dropping below normal for a
multi-day stretch for the first time in weeks. Lake effect snow
showers will finally diminish on Saturday as ridging starts to build
eastward across the Great Lakes. It will remain cold and dry
Saturday night into Sunday as surface high pressure moves overhead.

The next chance of more widespread snow will be late Sunday into
Sunday night as a warm front approaches from the Ohio Valley and Mid
Atlantic regions. Some guidance showing possible secondary
development, which could result in enhanced QPF, but too early to
discern this far out. Bottom line is that there will be a chance of
snow with isentropic lift associated with the system. Temps on
Monday could get warm enough for snow to chance to rain before
ending.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
Clouds should continue to slowly break apart and lift late this
evening as a ridge of high pressure builds into the Capital
Region. How quickly clouds break apart will be the challenge and
the main issue leading to fog potential tonight. Valley locations
should see more clearing than the higher terrain. That being said,
expect mainly VFR conditions at ALB/POU through the forecast
period with the potential for some MVFR BR during the early
morning hours. GFL has the best potential for IFR BR overnight
whereas PSF could be dealing with low IFR CIGS. Though, confidence
is fairly low at this time regarding the fog potential due to the
current cloud cover.

Winds will mainly be less than 10 kts from the southwest tonight
but will then turn out of the north as the ridge builds into the
region.

Outlook...

Tuesday Night: No Operational Impact. NO SIG WX.
Wednesday: Moderate Operational Impact. Chance of SHRA...SHSN.
Wednesday Night: Moderate Operational Impact. Chance of SHSN.
Thursday: Low Operational Impact. Slight Chance of SHSN.
Thursday Night: Low Operational Impact. Slight Chance of SHSN.
Friday: No Operational Impact. NO SIG WX.
Friday Night: No Operational Impact. NO SIG WX.
Saturday: Moderate Operational Impact. Chance of SHSN.

&&

.HYDROLOGY...
Active week with unsettled weather as multiple systems impact
region. Precipitation will fall mainly as snow with light QPF
amounts expected at this time. Potential for a more significant
lake effect event may evolve toward the end of this 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...BGM
NEAR TERM...BGM/JVM
SHORT TERM...BGM
LONG TERM...JPV
AVIATION...JVM
HYDROLOGY...IAA/BGM



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