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Area forecast discussion 
National Weather Service Albany New York
1257 PM EST Thursday Jan 29 2015

Synopsis...
high pressure will move to our east today. A fast moving clipper
type system will spread clouds into the region this afternoon...and
periods of snow tonight. Snowfall will be heaviest north and west of
the capital region where winter advisories have been issued. The
clipper departs tomorrow...but an upper level disturbance will keep
clouds and the chances for additional snow showers around. Much
colder air will follow Friday night and Saturday along with gusty
winds.

&&

Near term /until 6 PM this evening/...
as of 1257 PM EST...clouds continue to increase ahead of a fast
moving cyclone currently over SW Ontario and the eastern Great Lakes
region. Temperatures have warmed nicely over extreme eastern New York and western New
England where sunshine has occurred ahead of the high clouds. Maximums
were lowered a bit from the Hudson River Valley West. Highs temperatures
will generally be in the 20s with a few l30s over the Taconics and
western New England.

Latest wpc/GFS/CMC guidance is indicating a possible expansion of the
Winter Weather Advisory for the Schoharie valley...capital
region...northern Taconics...southern Vermont and northern Berkshires for 3-5 inches
of fluffy snow with snow to liquid ratios of 13-15:1. Adjustments
to the advisory will be at 330-430 PM update.

Some snow showers or light snow may reached the western dacks prior to
6 PM due to the isentropic lift ahead of the cyclone. The column
will take a little time to moisten based on the latest model
soundings upstream...and the 12z kalb radiosonde observation.

&&

Short term /6 PM this evening through Saturday night/...
winter weather advisories posted from 7 PM to 9 am Friday for the
Mohawk Valley...southern Adirondacks and Lake George Saratoga
region.

Precipitation so far has been scant with the clipper...but as it
crosses Lake Ontario...more moisture will be added to the feature.
Also...as it encounters colder air over our region...the isentropic
lift will increase as the aforementioned low level jet maximum barrels
New York state. Last but not least...vorticity will increase as a
middle level trough deepens and GOES negatively tilted.

As the aforementioned clipper type system works into New York
state...it will bring a burst of snow with its leading edge of an
associated low level jet maximum...maximizing isentropic lift.

Expect periods of snow tonight...while mostly light...should include
some elements of moderate snowfall rates approaching an inch per
hour. Also...a southerly flow ahead of the feature will likely
enhance snow rates across the Adirondacks...the northern rim of the
Mohawk Valley into the Lake George Saratoga region. That is where
the winter weather advisories were issued. In these areas...we
expect 3-6 inches of snowfall...generally highest over the elevated
terrain.

Further south across the capital region southward and eastward...
lesser amounts of snow are expected. The lowest amounts appears to
be the middle Hudson Valley into lower Litchfield County where around
only around an inch is expected. All remaining areas outside of the
advisory areas...including the immediate capital region and all of
adjacent western New England...look to get 2-3 inches...with some
localized 4 inch amounts over the higher terrain.

Low temperatures tonight will actually be above average for the time
of year...generally in the 20s...except for some teens across the
higher terrain.

Friday...the clipper will pass to our east with an Arctic front
perched to our northwest. Meanwhile...the upper trough will lag
behind...and a closed upper level low will form near New York City
by day/S end. The lagging trough will keep weak ascent translating
to sensible weather of clouds and scattered snow showers. The snow
showers will be most concentrated to the east of the capital region.

There should be some breaks of sunshine in valley areas by late in
the day. However...we will have to watch for the possibility that
the aforementioned upper low "captures" the clipper which will slow
down off the coast of Cape Cod...being "tugged" by the sharpening
middle level trough. If the surface low is captured fast enough...it
could produce a shield of snow as it rapidly deepens that could work
back into our extreme eastern sections of Massachusetts and Vermont. It is low
chance but a possibility. This scenario would bring additional snow
accumulations for these areas perhaps up to several quick inches.
Again...confidence in this scenario is low...but something to
monitor.

One thing this deepening storm will do is quickly drive the Arctic
front through by the end of Friday. Ahead of the
front...temperatures will be fairly close to normal...similar to
today/S highs...20s higher terrain...30 to 35 valley locations.

However...as the Arctic air is driven in...a pressure gradient will
result in rather strong gusty winds (but probably remaining below
Wind Advisory criteria) during the afternoon. Winds out of the
northwest could gust up to 40 miles per hour through early evening. These winds
will drive in much colder Arctic air Friday night. As a
result...temperatures will plunge to the teens below zero across the
Adirondacks...zero to 10 below across remaining areas north of the
capital region...zero to 10 above capital region southward. The wind
out of the northwest will average 10 to 20 miles per hour (with some higher
evening gusts) which could produce dangerous wind
chills...especially over the Adirondacks. Wind chill headlines might
need to be hoisted.

Saturday should be a mainly sunny but bitterly cold day. The wind
will abate some...but not entirely. High temperatures will only be
in the single numbers across the Adirondacks...teens most other
places...with a few lower 20s in the middle Hudson Valley and lower
Litchfield County.

Yet another weaker clipper and cold front will approach Saturday
night. For that reason...we feel temperatures will not get quite as
cold as we thought before (due to some clouds...and a slight south
or southwest breeze). They will still cold though with lows slightly
below zero across the Adirondacks...single numbers to around 10 from
the capital region southward. This clipper looks to bring scattered
snow showers to mainly our northwestern zones...possibly
transitioning into a period of pure lake effect snow showers.

&&

Long term /Sunday through Wednesday/...
Arctic frontal boundary is still expected to slide
southward...however...in the 00z guidance it seems this front will
progress a little further south on Sunday than what was prognosticated the
past couple of days. This will be a key feature for the pending
system for early next week. This storm too has recent trends
pointing further south track reducing its impact across the region.

Sunday...
Arctic boundary will likely develop some lake effect activity
downwind of Lake Ontario as h850 temperatures drop back to below -20c. The
best chance for snow showers will be into portions of the dacks and
western Mohawk Valley. It will be cold for this first day of
February as highs struggle to climb into the teens and lower 20s.

Sunday night into Monday...
as seen in the water vapor loop this morning...upper trough and ample
moisture coming ashore across Baja California California and Southern
California advecting into The Four Corners region.
Meanwhile...strong pv anomaly coming ashore across British Columbia
is expected to dive southeast into the long wave trough. The
interaction between this pv anomaly and moisture from The Four
Corners region intersect across the central/Southern Plains. As the
upper jet increases in magnitude...ageostrophic response increases
with surface pressure falls along the i70 corridor. The baroclinic
zone with the 00z runs are further south with the exception of the
Canadian model that would suggest a significant quantitative precipitation forecast event across the
entire region. A closer look at the European model (ecmwf)/GFS and the GFS ensembles
favor now a further southern solution. But it should be noted a few
members are further north /approx 30 percent of these members/. So
we will use that as our pop threshold +/- 10 across the region from
north to south.

Tuesday...
in the wake of this system...surface ridge builds into the region
with a rather tranquil yet chilly day setting up for our County warning forecast area. This
surface high is prognosticated to slide off the middle Atlantic coast later
Tuesday with some increase in cloud cover expected during the day.
From here...models diverge as we head into the middle week period.

Wednesday...
synoptic pattern favors another digging trough across the northern
plains and western Great Lakes region. What differs is if another
surface develops and moves across the region for another light snow
event /ECMWF/ or a slower more compact minimal system /GFS/. For
now...we will place a slight chance probability of precipitation.

Temperatures through the period will average below normal.

&&

Aviation /18z Thursday through Tuesday/...
VFR conditions will prevail into this evening...although ceilings will
gradually lower ahead of a clipper low pressure system approaching
from the Great Lakes. This system will move across region bringing a
widespread snowfall from late this evening into Friday morning...and
is expected to impact the terminals with prevailing IFR conditions.
Some improvement to MVFR will be possible between 16z-18z
Friday...but snow showers will linger.

Winds will be southerly around 4-8 kts until late Friday
morning...then shift to the northwest at 8-10 kts.

Outlook...

Friday night to sunday: no operational impact. No sig weather.
Sunday night: moderate operational impact. Chance of snow.
Monday: moderate operational impact. Chance of snow.
Monday night to tuesday: no operational impact. No sig weather.

&&

Hydrology...
no significant Hydro problems are expected through the next five
days.

Snow will fall tonight...with light amounts in the capital region
southward and eastward...moderate amounts to the north and
northwest.

Additional snow showers are possible Friday with generally minor
additional accumulations.

There is also the chance of snow Sunday night into Monday.

Ice will continue to thicken on rivers...streams...creeks...lakes
and other bodies of water.

The Eagle bridge gage on the hoosic river continues to be hampered
by ice effects.

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...none.
New York...Winter Weather Advisory from 7 PM this evening to 9 am EST
Friday for nyz032-033-038>043-082>084.
Massachusetts...none.
Vermont...none.

&&

$$
Synopsis...hwjiv/wasula
near term...wasula
short term...hwjiv
long term...bgm
aviation...jpv
hydrology...hwjiv/lfm

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