Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Albany New York
502 PM EST sun Dec 8 2013
hazardous travel conditions possible for the morning commute. Snow
will overspread the area tonight. Warmer air will work in and the
snow will mix with then change to sleet and freezing rain during
the morning. Eventually...a changeover to plain rain is expected
across most of the local area by afternoon especially up the
Hudson River valley and later in the day across the high terrain.
However...across the western Adirondacks...Lake George Saratoga
region and southern Vermont a changeover to just rain is not expected.
Near term /through Monday/...
winter weather advisories remain in effect for the forecast area
beginning at 10 PM this evening.
Until noontime Monday for the Mohawk Valley...Schoharie valley...greater
capital district...eastern Catskills...Taconics...Mid Hudson
valley...the Berkshires and Litchfield Hills where 1 to 3 inches
of snow is expected and up to one tenth of an inch of ice accretion.
Until 6 PM Monday for the southern Adirondacks...Lake George
Saratoga region and southern Vermont where 2 to 4 inches of snow
is expected and a trace of ice accretion.
The forecast remains on target for a widespread advisory criteria
event across the forecast area. No changes where made to the
advisories. Snow has final begun across the New York City
metropolitan area. The surface high continues to shift northeastward
across New England tonight. Cold air damming is occurring down the
Appalachians. The low has formed just of the middle Atlantic coast and
pressure fall are occurring to its north. Guidance shows the low
will form over the Great Lakes region. Both lows them move
northeastward and remain rather weak.
Used a blend of the GFS and NAM for the thermal profiles for
p-type and favor the colder NAM which seems to have a good handle
on the situation. Once the column moisten up snow will overspread
the area later this evening and overnight. By 10z enough warmer
air will have worked into the southern most portion of the
forecast for sleet and freezing rain. The threat for mixed
precipitation...sleet and freezing rain...will work northward up
through the capital district...Mohawk Valley and southern Vermont.
It should not be until the early afternoon farther north.
The changeover to rain is expected by afternoon up the Hudson
Valley into the capital district and across Litchfield. It will
take longer across the higher terrain of the eastern Catskills
... Into southern Vermont. While farther
north a changeover to just rain is not expected. Highs Monday are
only expected to top out in the 30s.
Chances for precipitation will decrease through the afternoon
Short term /Monday night through Tuesday/...
colder air will filter back in Monday night as the lows move away
from the region. The region will remain under the longwave trough
and a short wave trough will move through it approaching the
Great Lakes region Tuesday. This feature will bring chances for
snow showers to the western Adirondacks. Model guidance shows a
wave of low pressure will form along a frontal boundary stalled
well to our south and move off the southeast coast Tuesday in
response to southern stream energy. There are some indicates the
northern edge of the precipitation could reach the southern
portions of the forecast area. So in collaboration with neighboring
offices have chance probability of precipitation in for Tuesday during the day.
Temperatures will run about 5 degrees below normal.
Long term /Tuesday night through Sunday/...
the long term period will be characterized by frigid temperatures
and occasional lake effect snow.
A mean longwave trough and subsequent cyclonic flow aloft will
prevail across much of the northeast for the long term
period...allowing for below normal temperatures. These cold
temperatures will be held in place as fast-moving upper-level
impulses move through the flow aloft...bringing reinforcing shots of
cold air with them. At the surface...a strong area of high pressure
will remain anchored to the south of the region.
The question still remains exactly how cold it will get across the
region...especially regarding low temperatures. Model guidance
diverges significantly due to the progressive upper-level flow...so
have used a heavily-blended HPC approach. This blended approach may
result in a smoothing factor in the eventual temperatures...but
regardless it will be downright frigid across the region.
High temperatures will struggle to reach into the middle 20s across
valley locations...while failing to get out of the teens in higher
elevations. Low temperatures will be the coldest of the season thus
far...dipping well into the single digits across most of the
region...and below zero across portions of the Adirondacks.
The combination of cold temperatures and a brisk northwest wind
throughout much of the long term period will bring wind chill values
close to...if not reaching...advisory levels of -20f and below
Wednesday through Saturday...especially during the nighttime hours
across portions of Herkimer and Hamilton counties. Elsewhere...wind
chill values will still be frigid but look to remain above advisory
criteria. Will continue to mention the possibility of wind chill
headlines for portions of the Adirondacks in the severe weather potential statement.
Besides the cold...the anchored surface high pressure to the south
and the west/northwest flow aloft will help set the stage for a
potentially significant lake effect snow event across portions of
the western Adirondacks and possibly the western Mohawk River
valley. A long and likely multi-lake fetch off both lakes Erie and
Ontario coincident with likely moderate to Strong Lake-enhanced
instability given large Delta-T differences will result in a
prolonged lake effect snow event Tuesday night through
Thursday...with several inches of snow possible across portions of
Herkimer and Hamilton counties. For now...will continue mention in
severe weather potential statement...but lake effect snow headlines will likely be needed as the
event draws closer in time.
Another storm system may graze the region for the weekend...but
confidence in this scenario remains low given the large spread
amongst the model guidance as the upper level flow transitions to
more of a zonal pattern. Will continue to mention slight chance probability of precipitation
for the first half of the weekend before high pressure builds across
the region to end the weekend.
Aviation /22z Sunday through Friday/...
high pressure will move east of New York and New England this afternoon
with a complex storm system moving northeast from the Great Lakes
region and middle Atlantic corridor tonight. This storm system will
bring mixed precipitation to the terminals overnight into tomorrow.
VFR conditions are expected prior to 00z/Monday for kgfl/kpsf/kalb/kpou
aside for as patch of high MVFR stratus that drifted down the Mohawk
River valley into kalb/kpsf. A tempo group was used for the two
hours prior to 20z/sun to address this. Clouds will be thickening
and lowering from the south and west into the PM.
Over running precipitation ahead of an approaching warm front and a secondary
wave of low pressure will spread northeast...across the taf sites
between 01z-06z from south to north. The precipitation type will
initially be light snow based on the NAM/GFS model soundings and
critical thickness profiles. Our forecast slightly favors the colder
NAM soundings....although some sleet may also be mixed in at kpou
starting at 07z. The precipitation should transition to
sleet/freezing rain around 11z/Monday at kpou...with a mix of
snow/sleet at kalb and kpsf. Kgfl should hold as snow the longest
until 14z/Monday before mixing with sleet.
The precipitation will further transition to sleet and freezing rain at
kalb/kpsf between 12z-13z...and then to -fzra/-ra in the late
morning...as the surface temperatures warm above freezing. Kgfl might not
transition to freezing rain or rain until the afternoon. Kpou is
expected to go to rain by 14z/Mon. Ceilings and visibilities will gradually
lower to MVFR levels with the onset...and towards 12z...some IFR
conditions in terms of ceilings will be possible at all the taf sites.
Light/variable winds this afternoon will become east to northeast at
5 to 10 kts tonight into tomorrow...before veering to the southeast
to east by the late morning into the afternoon.
Monday night: low operational impact. Slight chance of rain...sn.
Tue: low operational impact. Slight chance of shsn.
Tuesday night: low operational impact. Breezy.
Wed: low operational impact. Breezy. Slight chance of shsn.
Wednesday night: moderate operational impact. Chance of shsn.
Thu: low operational impact. Slight chance of shsn.
Thursday night-Fri: no operational impact. No sig weather.
no Hydro related concerns are expected over the next 5 days.
Another round of precipitation tonight and Monday. The quantitative precipitation forecast will be
light with three to four tenths of an inch expected. In addition
most will be in the form snow. Otherwise...mainly lake effect
snows are expected during the week.
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 from 10 PM this evening to noon EST
Monday for ctz001-013.
New York...Winter Weather Advisory from 10 PM this evening to noon EST
Monday for nyz038>040-047>054-058>061-063>066.
Winter Weather Advisory from 10 PM this evening to 6 PM EST
Monday for nyz032-033-041>043-082>084.
Massachusetts...Winter Weather Advisory from 10 PM this evening to noon EST
Monday for maz001-025.
Vermont...Winter Weather Advisory from 10 PM this evening to 6 PM EST
Monday for vtz013>015.