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Area forecast discussion 
National Weather Service Albany New York
317 am EST sun Feb 1 2015

Synopsis...
Arctic high pressure will weaken across our region today. It will
not be as cold as Saturday...however temperatures will still be
below normal. A low pressure system passing to our south tonight
and Monday will bring a widespread significant snowfall to the
area. The heaviest snow is expected to develop before sunrise
Monday and continue through much of the day.

&&

Near term /until 6 PM this evening/...
as of 300 am...a clipper type system was located over the east end
of Lake Ontario. This moisture starved clipper and its associated
frontal boundary will move south and east of the region today. The
frontal boundary will stall near the PA/Massachusetts border and central New Jersey
westward into the Midwest/Ohio Valley. A 1030 hpa or surface
anticyclone will build in from southeast of James Bay. The skies may
become partly cloudy over the northern tier of the forecast area. H850
temperatures fall to -10c to -15c north and west of Albany...and -8c to
-10c to the south and east. Maximum temperatures will be a little warmer than
Saturday...but still below normal by 5 to 15 degrees with highs
in the middle and upper 20s from the capital region south and east
and teens to lower 20s to the north and west...with some single
digits over the southern dacks.

High clouds will increase over the southern tier in the afternoon...and
will thicken and lower towards 6 PM. Some light over running
snowfall may reach the southeast Catskills and middle Hudson Valley between 4-6
PM. Some slight and low chance probability of precipitation were introduced there...but a dry
column may yield quite a bit of virga at the onset.

&&

Short term /6 PM this evening through Tuesday/...
tonight and Monday a widespread significant snowfall event is
expected as a northern steam short wave combines with southern
stream moisture. The heaviest snow is expected to develop before
sunrise Monday and continue through much of the morning with snow
lingering through the afternoon before tapering off Monday evening.

All of the ingredients are in place for a significant snowfall as
a surface low pressure system tracks east from the Ohio Valley
late this evening to the middle Atlantic coast late tonight and
then passes southeast of Long Island on Monday. There is
considerable istentropic lift across our region ahead of this
system with some frontogenetic forcing at 700 mb around 18z on Monday
and a decent Theta-E plume h10-800 mb during Monday morning when the
snow should be the heaviest. Plume diagrams for Albany are
centered between 0.6 and 1.0 inch of liquid equivalent. Snow to
liquid ratios should be quite high for this storm generally in the
15-20:1 range. With all of this taken into consideration have
upgraded the final four zones up north to a warning such that now
the entire forecast area is in a warning. Expected snowfall totals
are 6 to 10 inches across the northern tier of zones with 8 to 16
inches elsewhere. The highest totals are expected across the
eastern Catskills...northern and central Taconics...Berkshires and
southern Green Mountains.

Behind this storm another shot of Arctic air descends across our region.
This along with a fresh snow cover will cause temperatures to
plummet Monday night. Lows are anticipated to drop to zero or
below across the forecast area with 10 degrees below zero and
colder across the southern Adirondacks. We may once again need
wind chill warnings and advisories for Monday night into Tuesday
morning and have highlighted in our hazardous weather outlook.

On Tuesday high pressure will quickly build into our region and
then pass to our east late in the day. Highs on Tuesday will once
again be very cold with readings only in the teens.

&&

Long term /Tuesday night through Saturday/...
the long term period will continue to feature below normal
temperatures...along with another chance for accumulating
snow...mainly light...associated with a clipper system late Tuesday
night through Thursday.

At the start of the long term period...a clipper system will be
approaching from the lower Great Lakes region Tuesday night with
scattered snow showers associated with warm air advection/isentropic
lift...primarily confined to upslope-favored areas of the southern
Adirondacks. Any accumulations Tuesday night are expected to be
light...generally under an inch.

The clipper system and associated better dynamics will move across
the forecast area Wednesday through early Thursday...with a light snowfall
expected for much of the region. Exact snowfall amounts are still
uncertain at this time...but a couple of inches across much of the
area is possible...with the best chance for accumulating snow across
the higher terrain.

One thing to keep an eye on regarding this clipper...is that there
is some uncertainty for later Wednesday into Thursday as to whether some
southern stream energy/moisture...currently located across northwest
Mexico...translates northeast and becomes partially phased with the
northern stream pv anomaly. Should this occur...as the 00z/01 European model (ecmwf)
and a few gefs members suggest...than a more prolonged period of
snow...and possibly greater amounts could result sometime between
Wednesday and early Friday...but this appears a rather low probability at
this time.

Assuming the clipper system remains weak/progressive and exits to
the east...an Arctic front should move across the region with
scattered snow showers lingering through the day Thursday. This
Arctic front will usher in another bitterly cold airmass across the
region Thursday night into Friday.

High pressure should then build across the region later Friday into
early Sat with dry weather expected. Another clipper system may
impact the region heading into late Sat and sun with another chance
for some snow or snow showers.

High temperatures Wednesday will moderate somewhat into the middle 20s
to low 30s across the region ahead of the clipper system...but only
range from the single digits to upper teens Thursday and Friday with
some locations in the middle Hudson Valley possibly reaching
approaching 20. High temperatures will rebound into the 20s for most
valley locations Saturday...with teens across the higher terrain.

Low temperatures Tuesday night will range from 5 below zero to 5
above zero...and on Wednesday night from near zero to the single
digits across the southern Adirondacks to low and middle teens across
the capital region...western New England and middle Hudson Valley.
Thursday night looks to be the coldest night with temperatures 5 to
15 below zero across the entire forecast area behind the Arctic
front. Wind chill headlines may be needed as well as a light
westerly wind allows wind chill values to plummet to 15 to 30 below
zero. Low temperatures Friday night will range from 5 below zero to
5 above zero...with wind chills generally 5 below zero to 15 below
zero.

&&

Aviation /08z Sunday through Thursday/...
a weak reinforcing cold front will approach from the northwest
overnight and Sunday morning...passing slowly southward across the
taf sites between middle morning and early afternoon. Clouds...and a
few flurries will be possible ahead of...and in the vicinity of
this front. Then...a storm system organizing over the Southern
Plains will track into the Ohio Valley Sunday night. This will
spread steady snow from south to north across the taf sites
beginning between 03z-07z/Mon.

Low clouds ahead of the aforementioned front will overspread
kgfl/kalb and kpsf through 08z/sun...and may reach kpou closer to
08z-10z/sun. Some flurries will be possible...especially at kalb and
kpsf. Ceilings should mainly remain VFR with bases of 3500-5000 feet
above ground level...but could occasionally approach MVFR...with MVFR ceilings more
likely at kpsf.

Clouds will continue into the day on Sunday...as some low level
moisture gets trapped beneath an inversion. As a result...broken
ceilings around 3500-5000 feet will be present through much of the day.
Meanwhile...mid/high level clouds will also increase ahead of an
approaching storm system over the Midwest. Snowfall associated
with this system will begin at the taf sites on Sunday
evening...but will likely not occur until after 03z Monday. Light
west to northwest winds will trend into the north-NE winds with the
passage of the front at speeds of around 5 kts.

Outlook...
Sun night-Mon: high operational impact. Definite snow.
Monday night: low operational impact. Slight chance of snow.
Tuesday-Tuesday night: no operational impact. No sig weather.
Wednesday-Wednesday night: moderate operational impact. Chance of shsn.
Thu: low operational impact. Slight chance of shsn.

&&

Hydrology...
no significant Hydro problems are expected through early next week.

A low pressure system passing to our south Sunday night and
Monday will bring a widespread significant snowfall to the area.

Continued below normal temperatures will continue to allow ice
to thicken on rivers...streams...creeks...lakes and other bodies
of water.

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...Winter Storm Warning from 9 PM this evening to 6 PM EST Monday
for ctz001-013.
New York...Winter Storm Warning from 9 PM this evening to 6 PM EST Monday
for nyz038>041-047>054-058>061-063>066-082>084.
Winter Storm Warning from midnight tonight to 6 PM EST Monday
for nyz032-033-042-043.
Massachusetts...Winter Storm Warning from 9 PM this evening to 6 PM EST Monday
for maz001-025.
Vermont...Winter Storm Warning from 9 PM this evening to 6 PM EST Monday
for vtz013>015.

&&

$$
Synopsis...iaa/11
near term...iaa/11
short term...11
long term...irl/kl
aviation...frugis/kl
hydrology...11

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