Area Forecast Discussion
Issued by NWS Albany, NY

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211
FXUS61 KALY 171116
AFDALY

Area Forecast Discussion
National Weather Service Albany NY
616 AM EST Fri Nov 17 2017

.SYNOPSIS...
Cold and brisk conditions in store for today, as high pressure
builds eastward across the region. A low pressure system will
approach from the lower Great Lakes on Saturday, bringing the
next chance for widespread precipitation. The storm system will
intensify Saturday night as it tracks northeast through the
Saint Lawrence River Valley, and will drag a cold front across
our region by Sunday morning. Colder air will filter in by
Sunday night, with lake effect snow developing downwind of Lake
Ontario.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 615 AM EDT...Colder air continues to filter in early this
morning, with a gusty northwest wind. There are still a few
light snow showers or flurries affecting mainly parts of the
Schoharie Valley and eastern Catskills. These are expected to
end within a few hours after sunrise, as a subsidence inversion
develops associated with high pressure building east from the
lower Great Lakes. It will remain breeze through much of the
daylight hours, as the ridge axis will not move overhead until
this evening. Winds will gust around 30 to 40 mph in favored
spots (Mohawk Valley, Capital District, Berkshires), especially
through this morning as winds speeds aloft beneath the
inversion of 30-35 kt are forecast. Temperatures will be cooler
than yesterday, with 30s across the higher terrain and lower to
mid 40s in the valleys.

High pressure will briefly move overhead tonight, which will
allow for winds to diminish and mainly clear skies with only
some high level cirrus clouds increasing overnight. These
conditions should result in substantial radiational cooling with
lows mainly in the teens to lower 20s across the area.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
Strong winds possible behind a cold front Sunday...

Saturday will start out cold and tranquil, although low
pressure will be deepening as it tracks northeastward from the
Midwest to the lower Great Lakes during the day. Clouds will
continue to increase and thicken ahead of the strengthening
storm system. Precipitation will develop generally from west to
east during the afternoon as isentropic lift on the 290-295K
surfaces increases ahead of the cyclone. Model trends each of
the last several days have slowed the onset of precip. Due to
the later arrival, low-level temperatures will have a chance to
warm up after the cold start due to increasing S-SW flow. Still,
there could be a brief period of snow/sleet in the Mohawk
Valley and southern Adirondacks where a brief dusting is
possible before changing over to rain. Much of the region will
have just plain rain as temps warm into the 40s during the
afternoon.

The surface cyclone is forecast to deepen to a sub-980 mb low
late Saturday night, as it tracks northeast along the St.
Lawrence Valley. Isentropic lift will continue Saturday night
ahead of the system`s cold front, so will maintain high pops
through the night. Model guidance in generally good agreement
regarding the track/intensity of the cyclone, except for the NAM
which is a considerable southern outlier. Will side more
towards the GFS/ECMWF/CMC solutions. The cold front should move
sweep through late Saturday night into early Sunday morning. As
temps aloft cool, some snow may mix back in across portions of
the Adirondacks before sunrise Sunday.

Behind the cold front, winds will shift to the W-NW and become
noticeably stronger during the morning. The parent cyclone will
continue to track northeast into southern Quebec as a sub-980
low, with cold advection resulting in deeper mixing to perhaps
800-750 mb. This could result in mixing down winds of 40+ kt to
the surface, especially across favored areas in W-NW flow such
as the Mohawk/Schoharie Valleys, Capital District and
Berkshires. While it is too early to determine exact wind speeds
this far out, will continue to mention the potential for at
least advisory level winds with 45+ mph gusts on Sunday. With
regards to precip, rain will end Sunday morning although snow
showers will develop as multiple short waves move through the
upper level trough. Some light accumulations will be possible in
mainly higher terrain areas. It will be difficult to organize
lake effect snow despite moderate lake induced instability due
to the oscillating flow associated with the short wave passages.

Lake effect snow may finally start to organize Sunday night
along the Mohawk Valley as winds align from the W-NW and an
upstream multi- lake connection likely develops with Lake
Huron/Georgian Bay. Some lake effect snow bands may even make it
down the Mohawk Valley and into the Capital District depending
on the flow trajectory. Otherwise it will remain brisk, cold and
breezy, although wind speeds will decrease somewhat compared to
earlier in the day.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
The extended forecast opens with Lake Effect snowfall impacting
locations west of the Hudson River Valley. There is still some
disagreement with the guidance on the orientation of the bands
and the favored low-level trajectory. Our forecast remains close
to the latest GFS with west to northwest flow with the
Schoharie Valley, west-central Mohawk Valley and eastern
Catskills being impacted on Monday early on, and then the band
or bands lifting northward into the western Adirondacks, as the
low to mid level flow backs to the west with high pressure
building in from the Carolinas. Some of the lake effect snow
showers may extends into the Capital Region, northern and
central Taconics, and the Berkshires with light accums.
Locations further to the west may receive light to localized
moderate amounts of snow. It will be cold and brisk with H850
temps running a couple of STD DEVs below normal based on the 00Z
GEFS with actual H850 temps in the -10C to -14C range early in
the day, and the warm advection occurs by the afternoon with the
ridge building in. The isolated to scattered lake effect snow
showers over the western Adirondacks/Mohawk Valley should end
Monday night. Highs Monday will be mainly in the upper 20s to
mid 30s in most locations, the exception will be the Capital
District, Mid Hudson Valley, and southern Litchfield CTY where
some upper 30s to around 40F readings are possible. Lows Mon
night will be mainly in the 20s.

Tue-Wed...High pressure ridges in from off the Mid Atlantic
Coast with moderating temps to above normal readings. Mid and
upper level heights rise across the Northeast ahead of the next
northern stream short-wave trough. H850 temps rise to-1C to +4C
from northwest to southeast across the forecast area. The medium
range deterministic guidance and the ensembles have this short-
wave trough arriving Tue night into Wed. In the warm advection
pattern, not much pcpn is expected with the warm front, and it
looks like the best moisture convergence is with the cold front
late Tuesday night into Wed. A slight to low chance of rain to
snow showers was kept in the forecast predominately north and
west of the Capital Region. A brief lake connection is possible
Wednesday afternoon west of the Hudson River Valley. Mild temps
on Tue will be in the upper 40s to lower 50s in the valley
areas, with upper 30s to mid 40s over the mountains. Lows Tue
night fall back into the upper 20s to lower 30s. Highs on Wed
will trend close to normal with the cold advection in the wake
of the front with 40s from the Capital District south and east,
and upper 20s to upper 30s for locations north and west.

Wed night into Thu...The mid and upper level trough axis moves
across the region Wed night with any multi-bands of lake effect
snow ending over the western Mohawk Valley, northern Catskills,
Schoharie Valley and western Adirondacks with light snow accums.
The chilly cyclonic flow will continue aloft over the Northeast
and southeastern Canadian with high pressure at the sfc
building in from the Midwest and Ohio Valley for Thanksgiving.
Temps will continue at slightly below normal readings for the
holiday.

&&

.AVIATION /11Z FRIDAY THROUGH TUESDAY/...
Low pressure continues to move into the Canadian Maritimes this
morning. The upper level trough continues to be over eastern NY
and New England. High pressure will build in over the region
this afternoon into tonight.

VFR conditions will continue at KPOU/ALB this morning with cigs
in the 3.5-5 kft AGL range. MVFR conditions persist at
KGFL/KPSF. The cloud bases will rise to VFR levels between 12Z-
15Z at KGFL/KPSF. Expecting the subsidence in the wake of the
cyclone, and the surface high building to erode the clouds
completely in the very late morning with clear to mostly clear
conditions by the early afternoon, and continuing into the early
evening. High to mid level clouds will begin to move into the
region after 06Z/SUN.

The strong sfc pressure gradient between the departing cyclone
into the Canadian Maritimes and high pressure ridging in from
the Midwest will allow gusty winds this morning into the
afternoon. Some deeper mixing from 1-2 kft AGL will allow for
west to northwest winds of 10- 18 KT with some gusts in the
22-30 KT range into the early afternoon. The stronger gusts are
expected at KPSF/KALB. The winds will decrease in the mid to
late pm with northwest winds of around 10 kts, and they will
become light to calm after 02Z/SAT.

Outlook...

Saturday: High Operational Impact. Likely RA.
Saturday Night: High Operational Impact. Breezy Definite RA.
Sunday: High Operational Impact. Windy Likely SHRA.
Sunday Night: Moderate Operational Impact. Breezy Chance of SHSN.
Monday: Low Operational Impact. Breezy Slight Chance of SHSN.
Monday Night: No Operational Impact. NO SIG WX.
Tuesday: No Operational Impact. NO SIG WX.

&&

.FIRE WEATHER...
Cold and brisk conditions in store for today, as high pressure
builds eastward across the region. A low pressure system will
approach from the lower Great Lakes on Saturday, bringing the
next chance for widespread precipitation. The storm system will
intensify Saturday night as it tracks northeast through the
Saint Lawrence River Valley, and will drag a cold front across
our region by Sunday morning. Colder air will filter in by
Sunday night, with lake effect snow developing downwind of Lake
Ontario.

&&

.HYDROLOGY...
No hydrologic problems are expected on the main stem rivers
through the next week.

High pressure will briefly build in today before a strong low
pressure system approaches from the Great Lakes Region on
Saturday. Widespread rain may begin as a mix with snow in the
western Mohawk Valley and southern Adirondacks but then quickly
change to to all rain that will continue through Saturday night.
A cold front will sweep through Sunday morning with additional
rain changing to snow over the higher terrain. At this time,
total QPF from this system looks to range from a half inch to
near an inch.

A colder air mass will then build in Sunday night through early
next week, with some lake effect snow downwind of Lake Ontario
affecting the western Adirondacks and Mohawk/Schoharie Valleys.

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...JPV
NEAR TERM...JPV
SHORT TERM...JPV
LONG TERM...Wasula
AVIATION...Wasula
FIRE WEATHER...JPV
HYDROLOGY...JPV



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