Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Albany New York
1242 am EST Sat Dec 7 2013
waves of low pressure will move eastward along a front
stalled to our south. Rain and sleet will change to snow late this
evening and taper off by late tonight after a light accumulation.
High pressure is expected to build in between waves for
Saturday...with the next round of precipitation expected Sunday
night and Monday. Initially snow is expected to overspread the
area Sunday night. However as warmer air moves in the snow will
mix with and change to sleet and freezing rain...with a changeover
to rain expected by Monday afternoon across most of the area.
Near term /through today/...
a Winter Weather Advisory continues for the central Mohawk
valley...helderbergs...ern Catskills...middle Hudson Valley...southern
Vermont...Berkshires...and Litchfield County CT through 7 am
As of midnight EST...a large trough stretches from the Pacific
northwest across The Rockies and northern plains...with a strong
ridge stretching from the eastern Gulf of Mexico across Florida
and towards the western Atlantic. In between these two
features...there is a surface boundary with broad SW flow aloft.
Steady precipitation has finally moved in across much of eastern
New York and western New England. The best returns have been across
southern and eastern areas...and areas from the capital region
north and West Haven/T really seen much precipitation yet at
all and will see very little additional accumulation. Precipitation is
still rain/sleet for valleys...with snow across the Catskills and
Berkshires. All areas should transition to all snow by around 1
am...with southeastern parts of the area taking the longest to
transition. Upstream radar imagery doesn/T show much precipitation
coming this way...and the recent trend in model guidance has been
lowering quantitative precipitation forecast...so this trend may be correct. The 00z kaly sounding
shows a lot of dry air below 850 hpa...and a lot of the quantitative precipitation forecast is
being lost to virga initially. Also...the low level flow is
N-NW...which is advecting drier air into the region as well.
As a result...we have lowered snowfall totals somewhat...with just a
coating for northern areas...around an inch or two for the capital
region and 1-3 for the middle Hudson Valley...southern Vermont...and northwest CT.
High terrain areas of the Catskills...Taconics...and Berkshires
still look to see 3-6 inches of snow.
The lows tonight will generally be in the middle to u20s with some
upper teens and l20s over the southern dacks...southern greens...and parts of
the eastern Catskills.
Tomorrow...some residual westerly upslope snow showers and flurries
may linger in the morning across Vermont...the Berks...western dacks...and
Taconics. Some lake moisture may be utilized in the west/northwest flow for
some snow showers and flurries over the western Mohawk Valley early in
the day. H850 temperatures fall to -10c to -15c north and west of the
capital region...with -5c to -10c readings south and east. A brisk
and cold day is expected for most of the region in the
afternoon...before some lake effect snowfall may materialize
downstream of Lake Ontario in the west/northwest flow late in the day into the
overnight. Initially dry air and low-level shear should inhibit
much of a lake band extension into the western Mohawk Valley/western
dacks/northern Catskills in the west/northwest flow. Some high chance/likely probability of precipitation
were used for southern Herkimer/northern Schoharie for light snow accums /an
inch or two/. Highs closer to the cold mav MOS values were used
with mainly middle and u30s in the valleys...and m20s to l30s over the
Short term /tonight through Monday night/...
more snow Sunday night transitioning to a mix wintry mix Monday
High pressure at the surface will continue to build in from the west
Saturday night and will eventually disrupt the favorable low level
flow for lake effect snows. A short wave trough will pass well to
our north across eastern Canada Saturday night with heights
beginning to rise across the region as ridging builds in aloft.
The longwave trough will deepen over the Continental U.S. Over the weekend. By
Sunday night...a low pressure system will develop over the Great
Lakes region in response to the northern stream energy...while
another low forms along the middle Atlantic coast in response to the
southern stream energy. Looking at the gfsensemble members and the
operational GFS and European model (ecmwf)...there are in good agreement with the
location of development and track of the lows.
The surface high will retreat northeastward across New England into
the Canadian Maritimes Sunday night and Monday. Cold air damming
will occur along the Appalachians. This along with a double barrel
low set up makes for a difficult forecast. Cold air will be in place
throughout the atmosphere supporting snow as the precipitation
overspreads the area. The coastal low will not become the dominant
low and is modeled to eventually be absorbed by the inland low as it
heads northeast into eastern Canada. This set up will allow warmer
air to work into the area beginning late Sunday night and through
Monday morning. The snow will mix with and changeover to sleet and
freezing rain. The questions are how much snow is expected before
the changeover then how long does the mixed precipitation last.
At this time...anticipating 2 to 3 inches of snow with the sleet
and freezing rain through the morning hours especially across the
higher terrain. Eventually the guidance indicates enough warming
occurs in the boundary layer resulting in a changeover to plain
rain across much of the forecast area by afternoon. Colder air
will be drawn back into the region Monday afternoon and night.
Long term /Tuesday through Friday/...
the period Marks the arrival of unseasonably cold temperatures...and
a long-lasting...strong westerly wind flow...which will mean
significant lake-effect snows across the western Adirondacks.
Despite high pressure dominating the northeast through the
period...lake-effect moisture will produce at least some extra
cloudiness for areas from the capital region on south and east.
Still...partial sunshine will be the general rule most days in these
areas. In the western Adirondacks...however...the snow will be the
rule...and far northern Herkimer and Hamilton counties will likely
receive significant accumulations.
High temperatures on Tuesday will range from around 20 degrees in
the western Adirondacks...to the middle 30s across our far south. Then
on Wednesday they will range from the middle teens to upper 20s...with
lower teens to middle 20s on Thursday. The first sign of moderation
will be on Friday...although all locations will still remain below
freezing. Lows Tuesday night will range from the middle-single-digits
to mid-teens...with lows Wednesday night from the single digits
below zero in the Adirondacks...to around 10 degrees above in the
extreme southern portion of our forecast area. Readings will bounce
back in the northern zones...with low values nearly everywhere in
the single digits.
Aviation /06z Saturday through Wednesday/...
through 08z/Sat...periods of light snow will continue at
kgfl/kalb/kpsf...with MVFR to IFR visibilities and possible ceilings. At
kpou...most of the precipitation should taper off by 07z/Sat...with
mainly MVFR conditions continuing.
After 08z/Sat...conditions should generally improve to MVFR/VFR by
10z. However...MVFR visibilities may linger until 13z/Sat at kpou...and
can not rule out some lower visibilities due to fog. Thereafter...expect
mainly VFR conditions at all taf sites through 06z/sun...with just
occasional VFR level clouds expected.
As for winds...expect mainly northwest to west winds at less
than 8 knots through sunrise...increasing to 8-12 knots by middle morning...with
some gusts possibly reaching 15-20 knots at times...especially at kalb and
kpsf. Wind speeds will decrease to less than 8 knots once again after
Sat night-Sun: no operational impact. No sig weather.
Sun night: high operational impact. Definite snow...sleet and freezing rain.
Mon: high operational impact. Definite snow...ra...fzra...sleet.
Monday night: moderate operational impact. Slight chance of shsn...fzra.
Tuesday-Tuesday night: low operational impact. Slight chance of shsn.
Wed: no operational impact. No sig weather.
no Hydro related concerns are expected over the next 5 days.
Waves of low pressure will move eastward along the front stalled to
our south. Snow will overspread much of the area this evening and
taper off by late tonight. High pressure is expected to build in
between waves...with the next round of precipitation is expected
Sunday night and Monday. Initially snow is expected to overspread
the area Sunday night. However as warmer air moves in the snow
will mix with and change to sleet and freezing rain with changeover
to rain expected by afternoon across most of the area. Looked
through meteorological model ensemble river forecasts (mmefs)and
at this time the rivers and streams are expected to only have
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.
CT...Winter Weather Advisory until 7 am EST this morning for ctz001-
New York...Winter Weather Advisory until 7 am EST this morning for nyz039-
Massachusetts...Winter Weather Advisory until 7 am EST this morning for maz001-
Vermont...Winter Weather Advisory until 7 am EST this morning for