Area Forecast Discussion
Issued by NWS Albany, NY

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FXUS61 KALY 091425
AFDALY

Area Forecast Discussion
National Weather Service Albany NY
925 AM EST Fri Dec 9 2016

.SYNOPSIS...
Lake-effect snow showers will continue to impact the region today,
mainly for areas west of the Capital Region and Hudson Valley, along
with cold temperatures and blustery conditions. Below normal
temperatures will be in place over the weekend with some additional
lingering snow showers and flurries for western areas.  A more
widespread snowfall is expected Sunday night into Monday, with the
potential for a moderate accumulation over much of the area.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
As of 925 AM EST...Narrow bands of lake-effect snow continue
across the region. The 12z KALY sounding showed 850 hpa temps
around -12 C and inversion heights around 6000 ft, which is more
than sufficient for allowing lake-effect to occur with lake temps
still into the 40s. The 0-2 km wind direction is around 305
degrees, allowing for multi-bands to impact the region, mainly for
areas west and southwest of the Capital Region. Although most
areas are only seeing very light showers and flurries, MRMS shows
there are a few areas (mainly across Montgomery and Schoharie
County), where locally more moderate snowfall is occurring. Most
spots only look to pick up a fresh coating today, although areas
currently under the narrow heavier bands may quickly see another
inch or two.

The 3km HRRR isn`t handling the lake-effect very well and seems to
have to end quicker than what will actually occur. The 4km BTV WRF
seems to do a little better job at keeping the lake-effect ongoing
through the day today, with the most persistent lake-effect bands
west of Albany. Most lake-effect looks to be fairly light, with
the better accumulations further west across central NY and closer
to the lake-shore, as usually occurs with a multi-band setup.

The bigger issue will be the brisk or blustery northwest winds
with deeper mixing in the wake of the sfc trough/secondary cold
front. H850 temps will lower to 1 to 2 standard deviations below
normal based on the latest 00Z GEFS. The H850 temps lower to -13C
to -16C across eastern NY and western New England according to the
latest GFS. Highs today may occur early in afternoon with the
blustery NW winds of 10-20 mph with gusts 30-35 mph. Highs will
generally be in the upper 20s to lower 30s in the valley locations
except for the mid-Hudson Valley/ NW CT where some mid 30s are
possible. Expect upper teens to mid 20s over the hills and
mountains.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY NIGHT/...
Tonight...The broad cyclonic flow aloft begins to weaken overnight
with the mid-level flow becomes more zonal. High pressure attempts
to build in from the TN Valley which will allow the winds to
slacken some. It will be cold with lows in the teens except over
the southern Adirondacks/southern Greens where some single digits
are possible. The wind chills may fall below zero over the
Adirondacks/southern Greens. A few lake effect snow showers or
flurries may persist well west of the Hudson River Valley.

Saturday...In the H500 quasi-zonal flow a weak mid level
disturbance tapping some Great Lakes moisture for lake effect snow
showers commences again in the west to northwest flow across
central NY and extending into the eastern Catskills and Mohawk
Valley. Some light snow accums of a coating to less than a half
inch will be possible in those areas. Otherwise it will be partly
sunny and cold with temps running at least 10 degrees below
normal. Highs will struggle to get above 30 degrees with 20s
across most of the region...and teens over the southern
Adirondacks and southern Greens again. A few lower 30s are
possible south of Albany in the Mid-Hudson Valley and NW CT.

Saturday night...A weak sfc trough lifts north with the flow
backing more to the west. The associated lake effect snow showers
push northward into the western Adirondacks. The mid and upper
level flow becomes more zonal. High pressure builds in from the
upper Mid Atlantic Region and PA for partly cloudy skies,
especially after midnight from the Capital Region south and east.
It will continue to be cold lows in the teens to around 20F near
KPOU. Some single digits are possible again over the southern
Greens and southern Adirondacks.

Sunday-Sunday night...Still some disagreement with the onset of
the over running pcpn ahead of a warm front south of the region
over the OH Valley and Mid Atlantic Region. This warm front is
tied to low pressure moving out of the Central Plains into the
Upper MS River Valley. The latest 00Z Canadian GGEM and GFS are in
pretty good agreement keeping it dry most of the day with clouds
thickening and lowering from the west...while the NAM/ECMWF are
much quicker increasing the clouds and have the warm advection
light snow beginning by the late morning into the afternoon. After
a blend of the guidance and collaborating with neighboring WFOs will
bring mainly chance pops in after lunch time with light snow
beginning with the increasing low and mid level warm advection.
Any snow accums will be an inch or so. Highs only reach the 20s to
lower 30s again.

Sunday night...This look like a different story as the guidance
converges on a strengthening low level baroclinic zone ahead of
the warm front. The strong differential thickness advection will
help increase the QG omega for light to moderate snowfall to break
out. Pops are increased to likely values, and the snow could
increase after midnight. The latest WPC winter guidance has 2-6"
of snow across the region with the higher totals of 4-6" south and
west of Albany. We currently have 1-3" of snow or so after
midnight and a general 2-5" snowfall for the entire night-time
period. There is still a lot of uncertainty in the timing and
evolution of the system, but it does look like a good overrunning
event. We will continue to mention a moderate snowfall in the HWO.
This could be our first widespread significant snowfall event of
the meteorological winter of 2016 for all of eastern NY and
western New England as we head into Monday.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
First, strong warm advection, low level jet energy, isentropic lift
and moisture advection throughout the day on Monday. Models suggest
that there will be a period of boundary layer temperatures in the
mid and upper 30s across the southern half of the area Monday
afternoon. So starting late Monday morning into the afternoon, a
wintry mix looks possible as the warm air surges further north
throughout the afternoon. Though, before the wintry mix, a period of
light to moderate snowfall looks likely with at least 1 to 3 inches
accumulation. Steadier precipitation ends Monday night and some lake
effect snow shower activity possible the rest of the night.

Much more spread in sources of guidance Tuesday through Thursday.
Some guidance suggests more quick moving upper impulses contributing
to some periods of larger scale synoptically-forced snow, while
other guidance supports more periods of lake effect snow shower
activity. With those sorts of uncertainties, keeping isolated to
scattered snow shower activity in the usual lake effect snow regions
of the southern Adirondacks, western Mohawk Valley Schoharie Valley,
eastern Catskills and southern Green Mountains with isolated snow
shower activity around those areas of terrain. There could be a more
organized band of snow showers along the leading edge of the strong
cold front Wednesday afternoon and evening.

Again, the one general agreement in the sources of guidance is that
the core of the coldest air should stay north of our region.
However, the northern stream upper pattern is amplified enough that
we will still see the coldest air so far this season locally,
especially after a strong cold front tracks through in the Wednesday
night time frame. In fact, lows Thursday morning may dip into the
single digits in the highest terrain and into the low and mid teens
elsewhere.

During the transition period before the strong cold front tracks
through our region, highs Tuesday and Wednesday will be in the
30s with 20s in the higher elevation. Highs Thursday will be over ten
degrees below normal,in the 20s, with teens in the higher
elevations.

&&

.AVIATION /14Z FRIDAY THROUGH TUESDAY/...
An upper level trough passage has shifted the winds to the
northwest. This has set up multiple bands of lake effect snow
streaming across the Capital Region this morning. These snow bands
will likely continue throughout day before becoming a bit more
scattered in the afternoon. Brief MVFR/IFR conditions are possible
within any snow bands that affect the TAF sites.

Models continue to indicate low ceilings this evening and overnight
tonight across all of the TAF sites with low level moisture hanging
around. So decided to trend the TAFs towards MVFR cigs (IFR cigs at
PSF). Though, confidence is still fairly low in the latter portion
of the forecast period.

Gusty northwest winds will continue through the TAF period with
gusts up to 20-25 KT possible through this afternoon. Winds will
damper this evening and overnight to between 5-10 KT.

Outlook...

Saturday Night: No Operational Impact. NO SIG WX.
Sunday: Moderate Operational Impact. Chance of SN.
Sunday Night: High Operational Impact. Likely SN.
Monday: High Operational Impact. Likely RA...SN...FZDZ.
Monday Night: Moderate Operational Impact. Chance of SN...FZDZ.
Tuesday: Low Operational Impact. Slight Chance of RA...SN.
Tuesday Night: No Operational Impact. NO SIG WX.
Wednesday: Moderate Operational Impact. Chance of SN.

&&

.HYDROLOGY...
Lake effect snow will continue today into tonight across areas
north and west of the capital region. The area for the highest
probability of snow will be across areas north and west of the
Capital Region. Light snow accumulations are expected for the
western Adirondacks,Mohawk and Schoharie Valleys and the eastern
Catskills.

A more substantial snowfall is possible Sunday night into Monday
night. At this time a light to moderate snowfall is possible with
total QPF currently forecasted in the one third to three quarters
of an inch range.

Flows will continue to lower in the cold air mass into the middle
of next week. No hydro problems are anticipated the next 5 to 7
days.

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...Frugis
NEAR TERM...Frugis/Wasula
SHORT TERM...Wasula
LONG TERM...NAS/JVM
AVIATION...JVM
HYDROLOGY...VTK/Wasula


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