Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Albany New York
945 PM EST sun Dec 8 2013
as a weak storm system approaches...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...making for
a hazardous morning commute. Eventually...a changeover to plain
rain is expected across most of the local area by
afternoon...especially for valley locations. Much of the remainder
of the upcoming week will be cold and dry...with some lake effect
snow showers across the Adirondacks.
Near term /through Monday/...
as of 945 PM EST...winter weather advisories continue across the
entire forecast area...beginning at 10 PM.
The 00z kaly sounding shows plenty of dry air below 700 hpa...so
it is going to take some time /and waste some quantitative precipitation forecast/ in getting the
column to moisten up. Regional mosaic radar doesn/T show much
precipitation upstream across central NY/PA. The best area of moisture is
now off the Jersey Shore/south of Long Island and moving away from
the area. Still...infrared satellite imagery shows plenty of cool cloud
tops over the central Appalachians with strong meridional
flow...and this is headed our way...so we should still be in line
to see at least some light precipitation later tonight.
Once the column moistens up...periods of light snow will
overspread the area...probably after midnight. Snow will be
rather light through the overnight hours...but all areas look to
have enough accumulation to at least coat the ground by
morning...although some areas may not see more than just that coating.
By 5-7 am...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...through the morning hours. It should not be
until the early afternoon farther north.
Temperatures will be warm enough to allow any precipitation to changeover to
rain by afternoon up the Hudson Valley into the capital district
and across Litchfield County. It will take longer across the higher
terrain of the eastern Catskills...Taconics...Berkshires into
southern Vermont. Areas further north may never change to plain
rain. Highs Monday are only expected to top out in the 30s.
Precipitation will be rather spotty during the late morning and into the afternoon
hours. The chance for precipitation decreases as the afternoon GOES on. There
will be a loss of ice in the clouds by the afternoon hours as well...so
precipitation may just be drizzle or freezing drizzle by that point.
Snowfall amounts will be light due to the limited amount of quantitative precipitation forecast
/generally 0.15 to 0.30 of liquid equivalent/. Total snow totals
will range from just a coating to 3 inches...highest in the
Adirondacks...Catskills...and Berkshires. Valley locations...such
as the middle Hudson Valley and capital region...will likely be on
the lower end of this range. Ice accretion up to a tenth of an
inch is possible as well...especially for the southern half of the
region...and the slippery coating of ice is reason why the
advisory remains in effect and looks to be the main threat through
the near term period.
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 /03z Monday through Friday/...
although flying conditions are currently VFR...they will be lowering
through the overnight hours from south to north as precipitation
associated with a storm system moves into the region.
Light snow will impact kpou by 03z...with a tempo for IFR
conditions due to visibilities between 03z-06z. Further north...kpsf
could see IFR snow as soon as 04z. Precipitation should be light once it
begins at kgfl/kalb around midnight...with flying conditions MVFR.
IFR visibilities/ceilings look to occur at kgfl/kalb by late tonight.
As temperatures warm aloft...snow will mix with sleet/freezing rain towards
Monday morning...especially for the southern terminals. Flying conditions
look to remain generally IFR through the entire day on Monday with
low ceilings in place. The precipitation will change over to rain by the late
morning...taking longest to changeover at kpsf. Precipitation will be
rather light and spotty through the day on Monday...and by
afternoon...there may be be pockets of drizzle or mist...as widespread
precipitation should have ended.
Surface winds will be light or nearly calm overnight. They will become
easterly at around 5 kts by late tonight...and eventually become
out of S-SW during the day Monday at light speeds.
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 until noon EST Monday for ctz001-013.
New York...Winter Weather Advisory until noon EST Monday for nyz038>040-
Winter Weather Advisory until 6 PM EST Monday for nyz032-033-
Massachusetts...Winter Weather Advisory until noon EST Monday for maz001-025.
Vermont...Winter Weather Advisory until 6 PM EST Monday for vtz013>015.