Area Forecast Discussion
Issued by NWS Albany, NY

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FXUS61 KALY 221145
AFDALY

Area Forecast Discussion
National Weather Service Albany NY
645 AM EST Wed Nov 22 2017

.SYNOPSIS...
A cold front will cross the region today with rain
showers and some snow at higher elevations. Brisk and cooler weather
this afternoon and evening in the wake of the front. Tranquil and
seasonably cool for Thanksgiving Day, but a few lake effect snow
showers are possible late in the day and at night over the
Adirondacks. Dry and a bit warmer for Friday, with some showers
possible by Saturday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 630 am, midlevel moisture streaming into the local area
both ahead of a digging shortwave over the Ohio Valley and from
a coastal low/inverted trough offshore of the southeastern US.
Band of radar returns associated with 925-700 mb frontogenesis
stretches from the Adirondacks into central New York and down
into central PA. Current obs suggest that some radar returns are
virga and some light precip is reaching the ground. Precip is
expected to start as rain or a rain/snow mix over the
Adirondacks before transitioning to snow. At lower elevations
toward the Mohawk Valley, mainly rain is expected this morning.

Lift associated with the upper wave/front, as well as the
coastal low, will continue to overspread the forecast area this
morning. The latter feature is expected to only deal a glancing
blow to our region. Moisture will increase with PWATs increasing
to 0.75 inches over the southeastern corner of our CWA, where
likely/categorical PoPs are in the forecast. Showers will also
continue along the approaching front, but are expected to
generally be light. Accumulating snow is expected to be confined
to the western Adirondacks, where locally up to 2 inches is
possible with highest amounts north of Route 28. Some light
accumulation is possible as the rain ends as snow over the
higher elevations of the Green Mountains this afternoon as
well, with up to an inch possible. Some areas of the Catskills
may see a couple tenths of accumulation as well, with plain rain
expected elsewhere. Colder air will be ushered in behind the
front on breezy northwesterly winds with temps likely falling in
the afternoon. Some gusts to 20-30 mph are likely in favored
areas of the higher terrain, Mohawk Valley, and Capital
District. A modest lake response may allow for some snow showers
for parts of the Mohawk Valley this afternoon into tonight, but
shallow moisture depth and fairly quick height rises should
greatly limit activity. Cloud cover will gradually clear late
this afternoon into tonight behind the front, with low temps
around 5F below normal in the mid-teens to mid-20s.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
Midlevel height rises will allow the surface high over parts of
the South and Ohio Valley to expand into the Northeast on
Thanksgiving, ensuring tranquil weather for the majority of the
forecast area. Baggy shortwave energy and midlevel warm
advection will allow mid and high clouds to increase into the
afternoon and evening, but given dry low levels expect a dry
forecast. Some modest lake response is forecast late in the day
into the overnight hours as winds go west-southwest, bringing a
chance for light snow showers to the western Adirondacks. High
temps Thanksgiving expected to be several degrees below normal.

Yet another quick-moving shortwave will result in a strong
surface low tracking across Ontario into James Bay Friday and
Friday night, with low and mid-level winds becoming
southerly/southwesterly locally. Though warm advection will be
delayed at the surface given rather light flow, temps are still
expected to rebound several degrees back toward seasonal normals
in the mid-30s to mid-40s. With a dry airmass and midlevel
height rises, a good deal of sunshine is expected. Fairly mild
Friday night with southerly flow continuing, although a few of
the usual suspects could decouple and see lower overnight lows.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
The extended forecast begins with an upper level trough approaching
the forecast area to open the weekend.  Initially, a warm front will
move through the region with mainly a slight to low chance of
showers.  The latest 00Z GEFS indicate H850 temps will be about 1 to
2 STD DEVs above normal, as the actual H850 temps will be around
+5C.  Highs on Saturday will range from the upper 40s to lower 50s
from the Capital District south and east, as upper 30s to mid 40s
will be common north and west.  The cold front to the system arrives
late in the day with very little low-level moisture to work with.
The better upper dynamics to the system shift well north and east
into Quebec.  There will be a slight to low chance of rain to rain
and snow showers across the region Saturday night.  Some likely PoPs
were used across the western Adirondacks, where some light snow
accums are possible of an inch or less with the frontal passage, and
westerly upslope flow in the wake of the front. Some light snow
accums are also expected across most of the higher terrain and the
western Mohawk Valley, which will be a half inch or less. Lows fall
back into the mid 20s to lower 30s.

Sunday-Sunday night...The mid and upper tropospheric trough lingers
over NY and New England.  In the cyclonic flow, lake effect snow
showers will continue especially west of the Hudson River Valley
across the eastern Catskills, west-central Mohawk Valley, and
western Adirondacks.  Additional light snow accums will be possible.
Right now, the flow looks to veer more to the northwest based on the
00Z GFS/ECMWF for multi-bands.  Some west to northwest upslope snow
showers will continue across southern VT.  It does look like high
pressure will be building in from the TN Valley, and Midwest Sunday
night helping to lower the subsidence inversion and allow the lake
effect snow showers to diminish overnight.  Brisk and cold
conditions are expected to close the weekend with highs only in the
mid 20s to lower 30s west of the Hudson River Valley, and over the
southern Greens with mid and upper 30s elsewhere.  Cold temps
are anticipated Sunday night with lows in the teens and 20s.

Monday into Tuesday...A moderating trend in temps is expected with
ridging building from the south and west.  Initially, the H500 flow
becomes zonal with temps slightly above normal on Mon, but then the
sfc anticyclone shifts offshore and the western Atlantic ridge
builds in with mid and upper level heights rising along the East
Coast.  The next cyclone looks to be approaching from southeast
Ontario and the Upper Great Lakes Region for the mid-week, but temps
could be about 10 degrees above normal TUE-WED with highs getting
into the upper 40s to lower 50s in the valley areas, and lower to
mid 40s over the mountains, which is closer to the latest WPC
guidance (which we sided with and coordinated with neighboring
WFO`s) over the colder superblend.  Overall, fair and dry late
November weather is expected for MON and TUE.

&&

.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
A cold front will approach from central NY this morning
bringing some scattered showers to eastern NY and western New
England. Low pressure will move along the boundary, but pass
south and east of the region across eastern New England this
afternoon. High pressure will gradually ridge in from the
Midwest tonight.

Mid and high clouds will continue to thicken and lower ahead of
the front towards daybreak. The better low-level convergence
associated with the front will arrive in the late morning into
the afternoon. Expect VFR cigs to lower to MVFR cigs /1.5-2.5
kft AGL/ between 14Z-18Z at the TAF sites in the showers. Some
reductions to MVFR vsbys will be possible /perhaps brief IFR
vsbys at KGFL/. There is a possibility of IFR cigs/vsbys at
KPSF, and a TEMPO group was used between 154-18Z there.

VFR conditions are expected to return between 18Z-22Z at all
the TAF sites, except for KSPF where some lingering high MVFR
cigs are likely to continue there. Sct-bkn stratocumulus will
become less in coverage early this evening. The skies will clear
overnight in the subsidence in the wake of the coastal system.

The light and variable in direction winds will increase and
shift to the west to northwest at around 10 kts in the late
morning into the early afternoon with the cold frontal passage.
In the afternoon, expect northwest winds of 10-15 kts with some
gusts in the 20-26 kt range. The winds will gradually diminish
early this evening to around 10 kts or less.

Outlook...

Thanksgiving Day:No Operational Impact. NO SIG WX.
Thursday Night: No Operational Impact. NO SIG WX.
Friday: No Operational Impact. NO SIG WX.
Friday Night: No Operational Impact. NO SIG WX.
Saturday: Moderate Operational Impact. Chance of RA.
Saturday Night: Low Operational Impact. Slight Chance of SHRA.
Sunday: Moderate Operational Impact. Chance of SHRA.

&&

.FIRE WEATHER...
A cold front will cross the region today with rain
showers and some snow at higher elevations. Brisk and cooler weather
this afternoon and evening in the wake of the front. Tranquil and
seasonably cool for Thanksgiving Day, but a few lake effect snow
showers are possible late in the day and at night over the
Adirondacks. Dry and a bit warmer for Friday, with some showers
possible by Saturday.

&&

.HYDROLOGY...
No hydrologic problems are expected this week.

An approaching cold front and coastal low will allow showers to
spread into the region today. Most of the moisture associated
with the coastal low will miss us to the east, so mainly light
precipitation is expected. Mainly dry and seasonably cool
weather is expected Thanksgiving Day into Friday, aside from
some light snow showers across the Adirondacks. Another round of
light precipitation is expected on Saturday ahead of another
cold front.

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



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