Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Albany New York
926 PM EST Wednesday Dec 4 2013
a weak high pressure system will move northeast...as we go
through the first half of Thursday into southern Canada. Cloud
coverage will increase as a low pressure system moving north from
the Great Lakes will have a trailing cold front associated with it
that will move through the region Thursday night into Friday
morning. After some possible light snow accumulations on Friday
night...the region will have tranquil conditions until the next
possible system on Monday.
Near term /until 6 am Thursday morning/...
solid clouds spreading north as middle and high clouds spread from
the west. Clouds are thin enough to allow temperatures to drop
quite a bit over the region...so more temperature adjustments this
evening...but once the clouds thicken...temperatures should hold
steady and begin to rise before sunrise. Radar and satellite
trends...and dry layers in area 00z soundings still suggest the
onset of any scattered precipitation would be more toward day
break in some areas and after daybreak in most other areas.
So...some adjustments to cloud over... precipitation chances adn
sky cover through tonight
Short term /6 am Thursday morning through Friday night/...
as we go into Thursday morning...a weak high pressure system will
move northeast into southern Canada. This will be followed by a
cold front that will make its way through western New York as we
go into Thursday afternoon associated with a low over the Great
Lakes moving northeast into eastern Ontario. High temperatures on
Thursday out ahead of the cold front during the day with a
southwesterly flow will be well above average ranging from the low
50s to upper 50s across the entire region.
This cold frontal system will be relatively slow moving as weak
upper level winds steer the front from west to east. Latest model
guidance suggest that as we go into Thursday evening...the cold
front will still be to the west of our region which will delay any
changeover from rain to wintry precipitation. Overnight low
temperatures on Thursday night will range from the upper 20s to
near 30 in the Adirondacks to the upper 30s in lower 40s south and
east of the immediate capital region.
As the cold front continues to move east Friday morning...the
transition from rain to a quick wintry mix to snow. The main
forcing for precipitation at this time will be right along the
cold front where highest elevations of the Adirondacks where
precipitation will change to snow first as t850 will range from
-1c to -4c and t925 will range from -1c to -3c early Thursday
morning. As the front progresses through the region during the day
on Friday...maximum temperatures on Friday will occur before the cold
front GOES through the region which will occur early in the day on
Friday north and west of the immediate capital region and later on
in the day on Friday south and east of the immediate capital
region. High temperatures on Friday will range from the middle 30s in
the Adirondacks to middle 40s across the middle Hudson Valley.
As we go from Friday afternoon into Friday evening with t850 and
t925 dropping below 0c throughout the day...latest model guidance
shows a series of low pressure impulses that will move northeast
along the thermal gradient. This in conjunction with good 850-700
hpa q-vector convergence and a good middle level stripe of
frontogenesis setting up off the midatlantic coastline Friday
afternoon...this will move northeast up to the southern coast of
Long Island as we get into Friday night...with additional moisture
from the Pacific that generated these low pressure impulses along
with an easterly flow off the Atlantic...this could be a set up
for light snow accumulations as we go into late Friday night. This
forecast will be updated however to take into account the timing of
the cold front as the main mesoscale forcing will be along the
passing cold front. At this time...latest probabilistic ensemble
members and latest model guidance shows the highest quantitative precipitation forecast values
south and east of the immediate capital region. The cold front
will exit the region later Friday night. Behind the cold
front...temperatures will drop Friday night with low temperatures
ranging from the upper teens in the Adirondacks to middle and upper
20s across the middle Hudson Valley.
Long term /Saturday through Wednesday/...
he period starts out on Saturday with a northwesterly flow regime
in place and colder air filtering into the region. There could be a
Minor Lake response with some lake effect snow showers across the
western Mohawk Valley and southwestern Adirondacks. However...high
pressure is forecast to build in fairly quickly by Saturday night
which should end any lake effect activity. Then colder and tranquil
weather is expected Saturday night through most of Sunday...as high
pressure drifts across the area then shifts northeastward into
southern Quebec and northern New England late Sunday.
Sunday night into Monday...a synoptic scale system is expected to
impact the region with potentially significant wintry precipitation.
Initially...enough deep layer cold air will be in place such that
snow will develop from south to north Sunday night...as isentropic
lift/warm advection increases considerably ahead of a dual-center
low pressure system lifting northward from the Ohio Valley and
eastern Seaboard respectively. Models in fairly good agreement with
regards to the main features with subtle differences...however due
to the primary low lifting northward through the Great Lakes and a
weaker secondary low expected along the New England coast...this
system will likely be dominated by southerly flow and warming aloft.
With a cold air remaining trapped in the low levels due to the
strong departing high pressure system...the result will be a complex
vertical thermal profile...with snow transitioning to some sort of a
messy wintry mix then eventually some plain rain later Monday.
Winter weather headlines will likely be needed with this system once
forecast confidence increases. Will continue to mention threat in
the severe weather potential statement.
In wake of this system there could be some leftover light rain
showers transitioning to snow showers Monday night...as colder air
wraps back in around the departing system. Tuesday through Wednesday
looks to feature colder temperatures and a westerly flow regime with
possible lake effect snow north and west of the capital region.
Based on current data...the flow trajectory would favor mainly the
western Adirondacks with a possible prolonged period of lake snows
through the middle of next week.
Aviation /03z Thursday through Monday/...
VFR conditions expected to prevail through the early evening
hours across the terminals...with just some passing scattered-broken middle
level clouds...especially from kalb northward.
Lower level stratus clouds are expected to increase later this
evening...as the flow turns more southerly. With lingering low level
moisture some light fog may also accompany the stratus. Conditions
are expected to deteriorate to MVFR then IFR late tonight as ceilings
lower and visibility becomes marginal as well. Warmer air will be moving
in aloft which will trap the low level stratus and fog...so
expecting IFR conditions to continue through 15z-18z Thursday.
Winds will be light and variable...becoming southeast around 3 to
7 knots Thursday morning.
thursday: moderate operational impact. Likely rain showers
Thursday night to friday: high operational impact. Likely rain
Friday night: moderate operational impact. Chance of rain...sn...sleet.
Saturday to sunday: no operational impact. No sig weather.
Sunday night: high operational impact. Likely snow.
Monday: high operational impact. Likely rain...fzra...sleet.
no Hydro related concerns are expected over the next 5 days.
Thursday night into Friday...as a strong cold front gradually
pushes through our region...a wave of low pressure will likely
produce a bit more significant rainfall across mainly our central
and southern areas where one quarter to one inch of rain could
fall. These rainfall amounts would be enough to produce some
within bank rises on main Stem rivers...however no flooding is
It will then turn colder after this system finally pushes through
Friday night with any additional precipitation falling as light snow.
It looks mainly dry Saturday into Sunday before the next strong
storm system approaches Sunday night into Monday. It looks cold
enough for mainly snow and/or mixed precipitation to fall with this
system at this time...possibly ending as some rain.
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.