Area Forecast Discussion
Issued by NWS Albany, NY

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000
FXUS61 KALY 300010
AFDALY

Area Forecast Discussion
National Weather Service Albany NY
810 PM EDT Wed Mar 29 2017

.SYNOPSIS...
After a dry and seasonable day on Thursday, another storm system
will impact the region for Thursday night through Saturday
morning. This storm system will bring a mix of snow, sleet and
rain to the area with several inches of heavy wet snow possible
in the higher terrain locations.

&&

.NEAR TERM /THROUGH THURSDAY/...
Northwesterly upper flow and a ridge of high pressure will ensure
tranquil weather through the near term. Clouds continue to
erode this evening as ridging builds in. Some high level cirrus
clouds are over-topping the upper ridge and will stream in
overnight. Expecting mostly clear to partly cloudy. Low
temperatures will be near seasonal normals mainly bottoming out
in the 20s.

A good deal of sunshine is expected much of the day Thursday, with
high and midlevel clouds increasing late. Should be good opportunity
to take advantage of the March sun angle to send temps back to near
normal, with light northerly flow putting a ceiling on highs. Sided
toward the higher end of MOS guidance for highs.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
     A Winter Storm Watch has been issued for Southern Vermont,
Northern Berkshires, Hamilton and Northern Warren counties from
Thursday night through Saturday Morning...

Quite a complicated and low confidence forecast for the storm
system set to impact us Friday/Saturday. In terms of the larger
scale pattern, a stacked low pressure system will lift out of
the central plains towards the Ohio Valley on Thursday. This low
is expected to track to our south across the Mid-Atlantic
region. At the same time, another weak northern stream feature
will be approaching out of southern Canada, although model
guidance suggest that these two features don`t fully phase at
they head towards the eastern United States. At the surface, the
initial low will track through the Ohio Valley on Friday, while
another low develops east of the mountains and rapidly develops
for Friday night as it heads east towards the western Atlantic
Ocean.

The main driver for our weather will be the potent southern
stream system, which will have ample moisture out of the Gulf of
Mexico and western Atlantic. As this storm approaches,
precipitation looks to break out from west to east on Thursday
night thanks to isentropic lift/warm air advection. With temps
both at the surface and in the boundary layer initially being
cold (along with wet-bulbing processes), precip looks to start
out as a period of snow for Thursday night into early Friday
morning. This will occur for both valley and high terrain areas,
with a light accumulation around 1 to 3 inches possible by the
morning commute (especially for areas west of the Hudson
Valley). Lows will generally be in the upper 20s to lower 30 on
Thursday night as precip begins.

The high pressure that provided the cold air mass to start will
be departing off the coast of New England on Friday morning. As
a result, through the morning hours, a persistent (although
light) east-southeast flow at low to mid levels, along with the
strong late March sunshine, will aid in warming the boundary
layer. It will be a battle between this warming and the cooling
of falling wintry precip for what p-type occurs. Ultimately,
model guidance suggest that valley areas looks to transition
over to rain or a rain/snow/sleet mix by afternoon, while higher
terrain areas remain a mix of snow/sleet. Bufkit data at
Pittsfield and Glen Falls shows an extended period of sleet.
Whereas at Albany, models indicate snow to to sleet to rain.
Warming aloft (around 800 hpa) could allow for an extended
period of sleet for some locations. The NAM model is much
stronger with the warming aloft whereas the GFS is not and keeps
the precip type more rain/snow. Therefore, there is much
uncertainty in the forecast in terms of total snow amounts and
precip type. If more sleet ends up mixing in, it will cut down
on snow totals but if temperatures remain colder, snow totals
could increase. For now, have 5 to 10 inches of snow in the
winter storm watch area where there is higher confidence of
colder temperatures and therefore more snowfall. Precipitation
will continue through dawn on Saturday as the upper low passes
by to our south but will then taper off during the morning
hours.

Temps area wide look to reach the mid to upper 30s Friday
afternoon but then drop off Friday night as winds turn out of
the north. Lows Friday night could dip into the upper 20s/low
30s in the higher terrain but remain just slightly above
freezing in the valleys. This could allow for precip to change
back over to snow Friday night.

This will all be a close call, as heavy precip could allow the
column to go isothermal at times, with precip falling as heavy,
wet snow, even in valley areas. Models and ensembles do suggest
plenty of QPF, with many showing over 1.00" liquid having
fallen by Friday night. For now, we have a few inches of snow
accumulation (4" or less) for valley areas, with accumulations
of 6"+ for the mountains, with the highest amounts across the
southern Green Mountains and the southern Adirondacks. Snow
ratios will be fairly poor through the event. Boundary layer
temps at or just above freezing will aid in some melting, making
the snow wet and dense.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
Things start out on a dry note, with a lack of cold air the
highlight over the entire period.  A dry and weakening cold front
from the north will break apart over the weekend, and high pressure
will build across the region, offering up decreasing cloudiness...
with a mostly sunny day for Monday while low pressure over Arkansas
moves into the Ohio Valley by Tuesday.

A good possibility of rain will overspread our forecast area Monday
night with a wintry mix the best bet for the higher elevations.  A
lack of cold air, and milder air being drawn in at mid-levels will
mean predominantly overrunning rain for Tuesday, with more overnight
mixing in the form of showers at the higher elevations Tuesday night
as the system moves off the Virginia coast.  Wednesday may see some
lingering rain showers as a slow drying trend begins.

High temperatures on Sunday will range from the mid 30s in the high
peaks of the Adirondacks...to around 50 degrees in the mid-Hudson
Valley. This will bounce by about 5 degrees for Monday except in the
mid-Hudson Valley, and Tuesday`s highs will be in the 40s, with some
readings around 50 degrees in the mid-Hudson Valley.  Wednesday will
be mildest, with highs ranging from mostly the upper 40s to around
60 degrees.

After Sunday night, low temperatures will moderate each night, so
that lows from the lower or mid 20s to the lower 30s both Saturday
night and Monday night become lows in the 30s and lower 40s by
Tuesday night.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
VFR conditions through the TAF period; 00Z/Friday. Clouds
continue to erode this evening as ridging build in. Some high
level cirrus clouds are over-topping the upper ridge and will
stream across the region overnight and Thursday. The cirrus
should be thin as the upper ridge continues to builds in from
the west.

Northerly winds will subside tonight becoming light overnight.
However gusty conditions will continue at KPSF this evening.
Winds will be northerly and light under 10 knots Thursday.

Outlook...

Thursday Night: High Operational Impact. Likely RA...SN...SLEET.
Friday: High Operational Impact. Definite RA...SN...SLEET.
Friday Night: High Operational Impact. Definite RA...SN...SLEET.
Saturday: Moderate Operational Impact. Chance of RA...SN...SLEET.
Saturday Night: Low Operational Impact. Slight Chance of SHRA...SHSN.
Sunday: No Operational Impact. NO SIG WX.
Sunday Night: No Operational Impact. NO SIG WX.
Monday: No Operational Impact. NO SIG WX.

&&

.FIRE WEATHER...
Much of eastern New York and western New England continues to have
snow on the ground. Although snow melt has been ongoing recently and
most valley areas only have snow depth of a few inches, much deeper
snowpack remains across the hills and mountains.

After a sunny and dry day Thursday with light northerly winds and RH
values bottoming out in the 30s, a strong late-season winter storm
will spread moderate to heavy precipitation throughout the region
Thursday night into early Saturday. This will result in a
continuation of moist and snow-covered ground.

&&

.HYDROLOGY...
The recent rainfall and snowmelt has led to some rises on rivers and
streams. A few river points came close or reached action stage, but
no flooding occurred. With daytime temperatures well above freezing,
some additional snowmelt is expected today and tomorrow, but no
precipitation is expected. This should allow rivers and streams to
continue to recede by through tomorrow.

Another storm system is expected on Thursday night through Saturday
morning. Precipitation will be snow initially, mixing with sleet and
rain especially in the valleys. Some of the higher elevations may
remain mainly snow and sleet. A total of 1 to 1.5" of precipitation
is expected, with some spots approaching 2". The wintry
precipitation will initially prevent much runoff from occurring.
Still, some river rises are expected by Friday into Saturday. The
MMEFS suggests a few rivers getting into action stage and
approaching minor flood stage.

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.
NY...Winter Storm Watch from late Thursday night through Saturday
     morning for NYZ033-042.
MA...Winter Storm Watch from late Thursday night through Saturday
     morning for MAZ001.
VT...Winter Storm Watch from late Thursday night through Saturday
     morning for VTZ013>015.

&&

$$
SYNOPSIS...Frugis/JVM
NEAR TERM...IAA/Frugis/Thompson
SHORT TERM...Frugis/JVM
LONG TERM...ELH/NAS
AVIATION...IAA
FIRE WEATHER...Frugis/Thompson
HYDROLOGY...Frugis/Thompson



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