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000
FXUS61 KALY 170009
AFDALY

AREA FORECAST DISCUSSION
National Weather Service Albany NY
709 PM EST Wed Jan 16 2019

.SYNOPSIS...
Cold and windy conditions are expected tonight with clearing
skies. Fair and cold weather is expected tomorrow before light
snow moves into the area for Thursday night into Friday morning.
A significant winter storm is expected late Saturday into
Sunday across the entire area.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
As of 709 PM EST...Cold front has crossed the forecast area and
temperatures are falling over all the area except the extreme
south. Blustery this evening with winds gusting up to 40 MPH.
Radar shows light snow showers over about two thirds of the
forecast area. A few locations may see a coating of additional
snow, but for most locations just some flurries. 7PM balloon
sounding showed well mixed boundary layer with dry adiabatic
lapse rate to 810mb - hence the windy conditions. Still
expecting skies to be mainly clear after midnight and with
diminishing winds, temps should drop off quickly late tonight.

Temps forecast to fall into the single digits to teens for
lows. Some parts of the Adirondacks will be in the single digits
below zero for tonight. Although winds will be decreasing by
late tonight, some wind chill values could reach as low as -10
to -18 over the Adirondacks.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/...
1030 hpa surface high pressure area will be passing over the
area for Thursday morning. This will allow for light winds and
clear skies. After a cold morning, temps will only warm up into
the teens and 20s for highs on Thursday. Some clouds will start
increase by late in the day, as the high starts shifting
offshore of eastern New England and the next system starts to
approach from the Ohio Valley.

A weak area of low pressure will be shifting from the Ohio
Valley towards the mid-Atlantic coast for Thursday night into
Friday. Weak warm air advection will allow some light precip in
the form of snow to develop across the area for late Thursday
night. It may take a little bit of time for this to occur, as
the very dry air mass at low levels will need to moisten up, but
most areas should see some light snow after midnight, lifting
northeast across the region. Limited moisture and weak forcing
will keep QPF rather low, generally just 0.05 to 0.20 of liquid
equivalent. Still, this will allow for about one to two inches
of snow across the whole area, which will make for a slick
morning commute on Friday morning. Precip should taper off by
the mid to late morning on Friday, as the best forcing shifts
east of the region. Some clearing in the clouds is expected on
Friday afternoon as temps rise into the mid 20s to mid 30s
across the area.

With zonal flow in place aloft, some lingering clouds are
expected for Friday night, but it should be mainly dry. Some
low-level cold advection should allow for some colder temps to
push into the area once again, with lows falling into the single
digits and teens across the area.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
Confidence continues to increase for a significant multi-hazard
winter storm impacting eastern NY and western New England Saturday
into Sunday. Main hazards include heavy snowfall amounts and rates,
possible period of sleet/freezing rain leading to ice accumulations
for some(mainly Catskills, mid-Hudson Valley, NW CT) followed by
strong winds/blowing snow potential and an arctic air mass that may
lead to dangerous wind chills Sunday night into Monday.

Strong 1035hPa high pressure in Quebec noses builds southward into
the Northeast during the day on Saturday with northwesterly flow
advecting in a chilly air mass across eastern NY and western New
England. High temperatures are expected to remain well below
freezing through the region with most staying in the teens and 20s.
As upper flow backs to the southwest, clouds continue thickening
through the day.

The 12z/16 global guidance has come into better agreement that for a
stronger moisture rich southern stream wave originating from the
Pacific Ocean will dig into the Gulf States and pick up additional
moisture from the Gulf during the day Saturday. As it travels
northeastward towards the Ohio Valley and warm air overruns the cold
air wedge over the Northeast, snow will begin from southwest to
northeast. Exact start time for snow is still uncertain but guidance
continues to suggest some light snow is possible Saturday morning
from weak isentropic lift before the more appreciable snowfall
associated with our winter storm overspreads the region Saturday
afternoon and especially after sunset.

Overnight Saturday, our southern stream wave moves into Ohio Valley
as a potent northern stream wave associated with a strong upper
level low and a very cold air mass over the Hudson Bay drops into
the Great Lakes. Global guidance has come into better agreement that
the two do not phase until during the day Sunday and this delay
would mean our intensifying storm tracks across the I-95 corridor
with the associated 850hPa low tracking from eastern PA across the
mid-Hudson Valley into eastern New England Saturday night into
Sunday. This has implications on the northern extent of our wintry
mix/snow line would keep it suppressed further snow to the mid-
Hudson Valley/NW CT/Berkshires with areas north and west likely
remaining all snow (perhaps brief period of snow/sleet). While the
first half of Saturday night likely remains all snow across eastern
NY and western New England with high snow ratios (dry/fluffy snow)
and possibly high snowfall rates given strong lift extending through
a deep column intercepting the dendritic snow growth zone, we could
then see the warm nose inch northward towards our area.

The second half of Saturday night looks to experience the strongest
warm air advection as our 850hPa jet intensifies to 50-60kts which
would warm the column and increase the fetch of Gulf/Atlantic
moisture reaching the Northeast. This would then shrink our
dendritic snow growth zone and even shift the "sweet spot"
experiencing the best lift through the -12C to -18C zone to the
Upper Hudson Valley and Adirondacks. While this would decrease snow
ratios for areas from the Greater Capital District south and
eastward, there is strong agreement amongst the global guidance that
a copious amount of moisture advects into our area with potentially
0.50 - 0.75 inches of liquid from 06z - 12z Sunday. In fact, the
snowfall band overnight Saturday resembles that of a quasi-
stationary snowfall band as described in previous CSTAR research.
Thus, even lower snowfall ratio closer to climatology (10 to 12:1)
would not limit significant snowfall accumulations and high snowfall
rates. Thus, our confidence for areas reaching warning criteria
snowfall continues to increase from the Capital District north and
west. For areas in the mid-Hudson Valley, NW CT, the Catskills and
perhaps the Berkshires, the warm nose could inch close enough the
mid levels warm close enough to or even higher than 0C that these
areas mix with sleet and even freezing rain. This could lead to ice
accumulations as the sfc-925 layer remains cold. Exact icing
potential is still uncertain but should be ironed out this event
draws closer. The ECMWF is the coldest solution limiting the wintry
mix to the far southern mid-Hudson Valley and NW CT with the CMC-NH
a bit farther north with the mixing potential while the GFS is the
warm outlier. For this update, again went with a ECMWF and CMC-NH
blend for precipitation type.

By Sunday, our northern stream and southern stream wave phase over
the Northeast allowing our positively tilted trough to become
neutrally titled. Snowfall continues into Sunday morning with cold
air quickly wrapping in behind our system with our warm nose quickly
shifting into New England. Any wintry mix Sunday morning should then
transition back to all snow during the day with snow ratios
increasing again. Winds during the day Sunday look to also increase
as the storm matures over New England with gusts up to 25-30 mph
possible potentially leading to blowing snow. Snowfall should linger
through most of the day Sunday before exiting from west to east late
in the day into Sunday night. Total liquid equivalent for this event
remains impressive with very good model agreement with 1 - 1.75
inches of liquid across the region which is why we continue to
believe this event will lead to significant snowfall amounts.

Very cold air continues advecting into eastern NY/western New
England Sunday night with 850hPa isotherms dropping to -19C to -28C
and surface lows falling into the single digits and even below zero
from the Capital District north/west. Strong winds continue
overnight as well with gusts 25 - 35mph possible which could lead to
dangerous wind chills and necessitate wind chill headlines.

Monday remains cold with temperatures likely only rising into the
teens and single digits. Winds stay breezy and with such cold
temperatures, it won`t take much for wind chills to reach dangerous
levels (-5F to -20F). Some lake effect snow showers are possible for
the terrain given arctic northwest flow over the lakes.

We should moderate by Tuesday with high temperatures warming into
the teens and 20s but the pattern turns active again by mid-week
with another possible system.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
Mainly VFR conditions forecast for the next 24 hours. KGFL, KALB
and KPSF could see a brief period of MVFR conditions in a light
snow shower or flurry this evening before skies clear around
midnight.

Gusty northwest winds to 35 kts this evening diminish to around
10 kts towards daybreak Thursday. Winds on Thursday forecast to
be light and variable.

Outlook...

Thursday Night: Moderate Operational Impact. Likely SN.
Friday: Moderate Operational Impact. Chance of SHSN...SN.
Friday Night: No Operational Impact. NO SIG WX.
Saturday: Moderate Operational Impact. Chance of SN.
Saturday Night: High Operational Impact. Definite SN.
Sunday: High Operational Impact. Definite SN.
Sunday Night: Moderate Operational Impact. Chance of SN.
Martin Luther King Jr Day: Low Operational Impact. Breezy NO SIG
WX.

&&

.HYDROLOGY...
No hydrologically significant precipitation is expected until
the weekend. Temperatures will remain mainly below freezing,
favoring continued ice formation/expansion on area waterways.

A powerful winter storm is set to impact the region over the
weekend. The precipitation type is expected to be mainly snow
with a wintry mix possible across the Catskills, mid Hudson
Valley, Taconics, Berkshires and NW CT. QPF could exceed an
inch with the potential for up to two inches in some areas.

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...SND/Frugis
NEAR TERM...SND/Frugis
SHORT TERM...Frugis
LONG TERM...Speciale
AVIATION...NAS
HYDROLOGY...Frugis/Thompson