Area Forecast Discussion
Issued by NWS Albany, NY

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS61 KALY 201803
AFDALY

AREA FORECAST DISCUSSION
National Weather Service Albany NY
103 PM EST Wed Feb 20 2019

.SYNOPSIS...
An approaching low pressure system will bring light snow late
this afternoon and into this evening, changing to a wintry mix
later tonight. It will become milder and mainly dry for Thursday
into Friday. Another storm system could bring a wintry mix
changing to rain Saturday night into Sunday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Winter Weather Advisory in effect for eastern New York and
western New England late today through early Thursday morning...

As of 1225 PM EST, not much change to the forecast at this time.
Deeper moisture continues to work its way into the forecast area
from the Gulf of Mexico per latest layered GOES16 water vapor
imagery. There are some light returns on radar entering the
mid-Hudson valley but NYS mesonet webcams only indicate snow in
Suffern and Warwick, which is far southern New York. However, as
the column saturates, snow should begin falling in the
Poughkeepsie area and then work its way northward throughout the
late afternoon and evening.

Prev Disc...
As of 950 am, high cirrus has overspread the region with
overcast skies throughout the forecast area. Temperatures are
tracking the current forecast well. Virga beginning to spread
into southern reaches of the forecast area, but given the
excessively dry airmass in place (PWAT 0.12/0.20 on the 12Z
KALY/KOKX soundings, respectively), it will take some time to
saturate the column. Closest snowfall observation is near
Williamsport/East Stroudsburg, PA, which is in line with latest
CAMs. Little changes were needed to the going forecast at this
time.

Previous discussion...

The system that will impact our region later today into tonight
is currently producing quite a bit of deep convection across
the Ohio Valley region and points south. Models suggest that
this convection translates eastward through the day, remaining
closer to elevated instability near and south of the Ohio River.
Heavier precipitation associated with this convection is
therefore expected to remain south and east of the region, with
additional heavier precipitation tracking into the Great Lakes
region closer to the main upper level system. The deeper
convection to our south may reduce moisture transport into our
region, resulting in relatively lighter QPF for our region with
this system. However, will have to watch trends closely in case
the heavier precipitation and embedded convective elements to
our south decrease more than expected, which could allow for
greater moisture transport and higher QPF into our region.

So, assuming we have the lighter QPF, clouds will continue to
thicken/lower through the day, with light snow developing across
southern areas (SE Catskills, mid Hudson Valley and NW CT)
between roughly 3-6 PM, and across central areas (the Capital
District of NY, Saratoga region, Mohawk Valley, and Berkshires)
between 6-8 PM. Snowfall accumulations of 1-2 inches could occur
by 7 PM across the eastern Catskills, mid Hudson Valley,
central and southern Taconics, and NW CT, with perhaps up to an
inch across the western Mohawk Valley, Capital Region and
central Taconics and Berkshires.

Areas farther north (southern Adirondacks, Lake George region
and southern VT) should have the snow begin generally after 8
PM.

Highs today mainly in the mid/upper 20s by mid afternoon,
although temps may fall a few degrees shortly after snow begins
due to wet bulb cooling effects.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/...
Tonight, snow will continue to overspread the entire region
between 8 and 10 PM. A few moderate bursts of snow will be
possible, especially across the Mohawk Valley and SW
Adirondacks, where isentropic lift will be strongest and should
coincide with added orographic effects. Snowfall rates of up to
one half inch per hour could occur, however the potential for
greater snowfall rates may be limited by the increasingly grainy
texture of the snow, due to relatively warm temperatures near
cloud top levels (generally -6 C to -10 C), with dry air above
H600 limiting cloud depth and potential for dendritic snow
crystals, especially after 10 PM.

The snow should then change to sleet fairly quickly from SW to
NE between roughly 10 PM and 1 AM, as a robust warm nose aloft
impinges on the region from the southwest, and then for areas
near and south of I-90, should mix with and/or change to
freezing rain after 1 AM. There could be some bursts of moderate
sleet at times.

Precipitation should begin to decrease in areal coverage and
intensity after 4 AM, as a deeper layer of mid level dry air
sweeps across the area from the west/southwest. However, low
levels will remain rather moist, so areas of freezing
drizzle/light freezing rain and some now grains should occur
during this time across most of the region.

Total snow/sleet amounts should range from 1-3 inches, although
locally higher amounts could occur across portions of the
eastern Catskills, and higher terrain of the southern Green
Mountains and northern Berkshires.

Total ice accretion from freezing rain should generally average
one tenth of an inch or less, although there could be some
isolated amounts up to one quarter of an inch across the
southern Berkshires and Litchfield Hills, and possibly the
western Mohawk Valley.

As a strong low level jet translates northeast across the
region, strong wind gusts may occur across higher terrain of the
SW Adirondacks, eastern Catskills, and the climatologically
favored areas of the southern Greens, Berkshires and
north/central Taconics, where southeast winds may gust up to
30-40 mph for a short duration, roughly between 10 PM and 2 AM.

Low temperatures will be this evening, mainly in the 20s, with
slowly rising temps after midnight, reaching the lower/mid 30s
across many areas south of I-90 by daybreak, with upper 20s to
lower 30s to the north.

For Thursday, areas of freezing drizzle and drizzle may linger
through mid morning, with the freezing drizzle mainly for the
southern Adirondacks, Lake George Saratoga region and southern
Vermont, where temps may be slower to rise above the freezing
mark. For this reason, have extended the end time of the
northern portion of the Winter Weather Advisory until 10 AM
Thursday morning.

As an occluded front sweeps eastward, deeper mixing should
commence from west to east later in the morning through early
afternoon, allowing for a spike in temps. So, highs may reach
the 40s in valley areas by early afternoon, and perhaps near or
over 50 across the mid Hudson Valley. It also should become
windy by afternoon, with west winds increasing to 15-25 mph,
with some gusts of 30-40 mph possible.

Lots of clouds should dominate areas along and north of I-90 for
Thursday night into Friday morning, with some snow showers even
possible across the SW Adirondacks. Clearing is expected from SW
to NE Friday afternoon, with mainly clear and chilly conditions
expected Friday night.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
System that originates from the SW U.S. ejects NE tracking through
the central U.S. and into the Great Lakes by Sunday.  There is an
increasing consensus that the upper system is a closed low that
tracks around the northern periphery of mean flat upper ridging in
eastern North America.  The closed upper low then tracks north of the
U.S./Canada border Sunday through Monday.

Clouds and precipitation spread into our region by Saturday evening,
which should be mainly rain but some mix of rain and snow in higher
terrain. Highs Saturday in the upper 30s to lower 40s but mid 30s
higher terrain.

Precipitation mixes with some sleet and freezing rain in northern
areas and parts of the eastern Catskills, Schoharie Valley,
Berkshires and southern VT as some wet bulb cooling of low level
temperatures is possible. There should be a cold rain in all other
areas. Stronger warm advection Sunday morning is expected to change
the mixed precipitation to rain. Rain becomes showers as coverage
decreases when the upper system and associated cold front depart.

Highs Sunday in the mid 40s to around 50 but lower 40s northern
areas. There is an increasing consensus that the low level pressure
gradient will increase significantly with the rapid deepening of low
pressure. Some very strong west to northwest winds are likely late
Sunday afternoon through Sunday night and much of Monday.  Wind
headlines may be needed once we get closer to the weekend and more
details about specifics are available.

Dry weather is expected Monday and much of Tuesday with winds
diminishing Monday afternoon and night as low level ridging centers
itself over our region.  Highs Monday in the mid 30s to around 40
but mid to upper 20s and some lake effect snow shower activity into
the southern Adirondacks.  Highs Tuesday with clouds potentially
increasing ahead of the next system, in the 30s but lower to mid 20s
northern areas.

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
Moisture continues to spread into the region from the south as
high pressure shifts east. Virga appearing on area radars
suggests column is beginning to saturate. This process should
occur from south to north with flight categories falling to
borderline MVFR/IFR in light snow beginning at KPOU around 20Z,
KALB/KPSF around 22Z, and KGFL around 00Z. The snow should
begin mixing with sleet after around 3-5 hours from the time it
starts, then to freezing rain 1-2 hours later. Forecast
soundings suggest the potential for some freezing drizzle during
lighter periods of the snow. This will be addressed in future
amendments if it appears plausible. Cigs/vsby in the overnight
period should hover near the border of MVFR/IFR. As the steadier
precipitation tapers off around 10-12Z Thu, some patchy drizzle
will be possible (perhaps freezing drizzle at KGFL where temps
will remain below freezing) which could allow for a period of
IFR conditions through around 14-15Z. Cigs/vsby should begin to
improve after 15Z as diurnal heating and the approach of drier
air begins to mix out the low-level moisture.

Winds will generally be from the south at 10 kt or less through
the overnight period, shifting to west-southwest at 5 to 15 kt
with some gusts in excess of 20 kt late Thursday morning into
the afternoon. A brief period of marginal low-level wind shear
conditions are expected between about 02-10Z, although southerly
surface winds at KALB may be elevated enough to avoid LLWS
concerns.

Outlook...

Thursday Night: Low Operational Impact. Breezy NO SIG WX.
Friday: No Operational Impact. NO SIG WX.
Friday Night: No Operational Impact. NO SIG WX.
Saturday: No Operational Impact. NO SIG WX.
Saturday Night: High Operational Impact. Likely RA...SLEET.
Sunday: High Operational Impact. Breezy Likely SHRA...RA.

&&

.HYDROLOGY...
Hydrological impacts are not expected through at least Saturday.

Seasonably cold weather is expected through today, promoting
additional ice expansion on area waterways.

The next system arrives late this afternoon into Thursday
morning with snow transitioning to a wintry mix. Liquid
equivalent amounts of generally a quarter to a half an inch are
expected. Temperatures are expected to run a bit above normal
Thursday into the weekend.

Another period of rain or mixed precipitation is possible
Saturday night into Sunday.

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...Winter Weather Advisory from 4 PM this afternoon to 7 AM EST
     Thursday for CTZ001-013.
NY...Winter Weather Advisory from 4 PM this afternoon to 7 AM EST
     Thursday for NYZ047-058>060-063>066.
     Winter Weather Advisory from 7 PM this evening to 7 AM EST
     Thursday for NYZ038-040-048>054-061.
     Winter Weather Advisory from 7 PM this evening to 10 AM EST
     Thursday for NYZ032-033-039-041>043-082>084.
MA...Winter Weather Advisory from 7 PM this evening to 7 AM EST
     Thursday for MAZ001-025.
VT...Winter Weather Advisory from 7 PM this evening to 10 AM EST
     Thursday for VTZ013>015.

&&

$$
SYNOPSIS...KL/Thompson
NEAR TERM...KL/Thompson/JLV
SHORT TERM...KL
LONG TERM...NAS
AVIATION...Thompson
HYDROLOGY...KL/Thompson


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.