Area Forecast Discussion
Issued by NWS Albany, NY

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383
FXUS61 KALY 100546
AFDALY

Area Forecast Discussion
National Weather Service Albany NY
1246 AM EST Sat Dec 10 2016

.SYNOPSIS...
Light lake effect snow showers and flurries will continue to impact
locations mainly west of the Capital Region and Hudson Valley with
cold conditions this morning. Below normal temperatures will be in
place over the weekend, with some additional snow showers and
flurries for areas mainly north and west of Albany through today. A
more widespread snowfall is expected Sunday afternoon into Monday,
with the potential for a moderate accumulation over much of the
area.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
As of 1246 AM EST...The lake effect multibands continue to weaken
considerably south and west of the Capital Region based on the
KENX and regional mosaic radars. The 00Z KALY soundings show the
subsidence inversion lowering to 5-6 kft AGL. The low level flow
continuing to veer and the inversion lowering is helping to
squelch the narrow lake effect bands. A coating to a tenth or so
is possible over the eastern Catskills and parts of the Schoharie
Valley.

It remains variably cloudy across the region and temps continue to
fall off into the teens in the valleys and over the hills. Single
digits to lower teens over the mountains. The winds continue to
subside to 5-10 mph.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH MONDAY/...
Saturday-Saturday night, a shortwave currently located over the
northern Plains/south central Canada will approach Saturday
afternoon and evening. As this approaches, low level winds should
start backing more into the west/southwest. This flow will
maximize the over water trajectory of Lake Ontario, which in
combination with synoptic lift from the approaching disturbance,
should allow for snow showers to increase across the western
Mohawk Valley and western Adirondacks Saturday afternoon and
night. In fact, there is a possibility that snow showers could
organize into a single band once again and bring a period of
moderate snowfall to portions of northern Herkimer and northwest
Hamilton CO Saturday evening. For now, have accumulations of 1-3
inches in this general area, but trends will need to be watched
for the potential for a more organized single band and greater
accums. Elsewhere, some snow showers/flurries may extend into
valley areas north of I-90 and into southern VT Saturday
afternoon/evening, with additional coatings to less than an inch
possible. Otherwise, it will remain cold, with highs mainly in the
20s to lower 30s, and overnight lows in the teens with some single
digits possible.

Sunday-Monday, model consensus continues to tighten regarding a
more widespread precipitation event during this time period,
although still differ somewhat with respect to potential
low/mid level warming, storm track and also QPF. The 12Z/09 ECMWF
and GFS remain on the colder side of guidance, with a possible
secondary low developing near LI/southern New England and trapping
low level cold air in place. The 12Z/09 NAM on the other hand is
warmer with less secondary development. The 12Z/09 GEM is colder,
but also seems to suggest less QPF across our region, with greater
low level convergence potentially remaining closer to the
secondary low development to our southeast and limiting overall
moisture inflow into our region. At this time, we utilized a blend
of most models for QPF, but also on the colder side of guidance,
with some light snow or flurries developing Sunday afternoon with
mainly minor accumulations of an inch or less, then steadier snow
for Sunday night/early Monday morning, before potentially
transitioning to a wintry mix or light rain/drizzle Monday
afternoon. Very preliminary snowfall amts of 3-6 inches are
currently indicated for the I-90 corridor and most areas to the
south, with the greatest amts closer to I-90, as well as higher
elevations of the Berkshires and eastern Catskills. North of I-90,
slightly higher amts of 6-8 inches are indicated, except locally
greater across higher terrain of southern VT.

Again, very preliminary totals which likely will change as
additional data become available, and also greater confidence in
forecast secondary low pressure development/thermal profiles
occurs. There still remains at least a possibility of either
quicker low level warming, or overall less QPF which would reduce
these snowfall amts.

Sunday high temperatures should remain below freezing, mainly in
the 20s to lower 30s, then 20s for Sunday night, before slowly
rising into the mid 30s in valley areas from Albany south and
east Monday afternoon, with mainly lower/mid 30s elsewhere.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
The polar vortex will make its return as below normal height
anomalies return across the Great Lakes and Northeast through the
mid-week period.

Subtleties remain in the global models, especially along the
southern periphery of this vortex as a short wave originating from
the Northwest Territories rotates around this large vortex with
chances for light snow into the middle of the week.  The GFS and
GGEM are hinting at a surface wave amplifying over the middle
Atlantic region and tracking northeast along or near the New England
coastline.  The ECMWF is much more progressive with a strong
baroclinic zone near the I-80 corridor with any threat of snow
mainly south of the region.  For now, per the ensemble blends, we
will leave in mainly chance PoPs through the period.  The higher
PoPs will be confined mainly downwind of Lake Ontario where lake
effect parameters remain favorable where additional snow
accumulations are expected.

As for temperatures, below normal as those H850 temperatures settle
an average of -10C beginning Monday night then at or below -20C by
Thursday. Highs mainly into the 20s and 30s early on in the long
term then dropping back to the teens and 20s with overnight lows
mainly into the teens and 20s with single digits possible Wednesday
night into Thursday morning.

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
VFR conditions will prevail through the forecast period with the
Capital Region under the influence of high pressure. A broken to
overcast 4-6k cloud deck may build in this afternoon but otherwise,
any clouds should be scattered in nature. Winds will be 10 kts or
less mainly from the northwest through the period.

Outlook...

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

&&

.HYDROLOGY...
Lake effect snow will continue tonight and Saturday across areas
west of the capital region. Additional light snow accumulations
are expected for the western Adirondacks, Mohawk/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...KL/Wasula
NEAR TERM...Wasula
SHORT TERM...KL
LONG TERM...BGM
AVIATION...JVM
HYDROLOGY...VTK/KL/Wasula



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