Scientific Forecaster Discussion
fxus61 kaly 301037
Area forecast discussion
National Weather Service Albany New York
637 am EDT Thu Mar 30 2017
high pressure will allow for a dry day today with
seasonable temperatures and a partly to mostly sunny sky. Clouds
will increase this evening ahead of an approaching storm system that
will bring snow, rain and sleet to the region for late tonight
through early Saturday. Some areas, especially northern and high
terrain areas, may see significant snowfall from this storm.
Near term /until 6 PM this evening/...
as of 627 am EDT...an upper level trough continues to depart
off the coast of Nova Scotia, while weak shortwave ridging is
building into the area from the Great Lakes and Ohio Valley. Infrared
satellite imagery shows all the clouds of the backside of this
trough have shifted eastward, resulting in mainly clear skies
over the area, with just some thin cirrus around right now.
Surface high pressure is located over Quebec and this high
pressure area will continue to slide eastward through the day
today. Although the morning will start off fairly clear, mid and
high level clouds ahead of the next advancing storm system are
already over western New York. These should reach our area by
the afternoon, allowing for increasing clouds later in the day. Winds
will be lighter than yesterday thanks to the nearby high
Temps aloft are still fairly cool, generally around zero to -5
degrees c at 850 hpa. Mixing should be close to 850 hpa today
with the strong late March sunshine and temps look to reach the
mid 40s to low 50s for most areas.
Short term /6 PM this evening through Saturday night/...
late season winter storm to impact the region...
A potent closed off low at 500 hpa will slide across the Ohio
Valley for tonight into tomorrow. This stacked low pressure area
will have a surface low that heads towards the eastern Great
Lakes, while another low pressure area forms east of the
Appalachian Mountains and heads east into the Atlantic for
Friday evening into Saturday morning.
Although this evening will start off dry with increasing clouds,
there will be the chance for some snow by about midnight for far
western areas, as increasing warm advection/isentropic lift
allows an area of steady precip to slide eastward across
western and central New York. Precip could initially be in the
form of rain if the boundary layer hasn't cooled off enough, but
wet-bulb effects should allow precip to go over to snow for
most areas as the precip heads eastward across our area through
the late overnight hours, as surface temperatures fall into the
upper 20s to low 30s. All areas will be seeing precipitation by
daybreak Friday, with up to an inch or two of snowfall already
having fallen by 7 am Friday possible for areas west of the
With a low-level jet out of the south at 30-35 kts, temps aloft
will be warming on Friday morning. This will allow some sleet to
start to mix in for the western Mohawk Valley, eastern
Catskills, Mid-Hudson valley and northwest CT. This mixing with sleet
will gradually shift north and east through the morning hours,
reaching the capital region by about mid morning or so. It's
still uncertain exactly how far north this mixing with sleet
will get, as the more aggressive NAM would suggest sleet would
eventually occur across much of the area. Meanwhile, the GFS and
even the ECMWF, as a little further south with the storm track,
and keep the mixing line further south.
In addition, the low level flow out of the east to southeast,
along with strong late March sunshine, will aid in helping to
warm the boundary layer. While these factors would favor a
transition over to rain for valley areas, precip intensity could
counteract these effects and keep p-type as snow (especially
for northern areas, where the cold air is a little deeper
through the column).
Steady precipitation will continue through the entire day Friday
with temps stuck in the low to mid 30s. We do seem to think that
valley areas (including the greater capital region) should see
mainly rain by Friday afternoon, however, any heavier bursts of
precip could allow for snow or sleet to mix in or changeover
from time to time, as the heavier precip forces the temp profile
to go isothermal. Meanwhile, higher terrain areas in the
Berkshires, Adirondacks, northern Taconics and southern greens
look to remain mainly snow during this event.
Snow ratios will be poor, due to the wet and melting nature of
the snowflakes and the dendritic growth zone being so high up.
The heavy wet snow could result in some power outages. It's
still unclear how easily the snow will stick on roadways due to
the warmer ground temps and occurring during the daytime.
However, past late-season storms have shown that if snow falls
hard it enough, it will stick anywhere.
Precip looks to continue into Friday night, as the secondary
surface low develops. This should aid in allowing the temps
aloft to start to cool off, and end the threat for sleet, with
primarily snow and rain by late Friday night. Some areas that
were seeing rain may start to see more and more snowfall into
Friday night, although precip intensity and amounts will finally
be starting to taper down by this time. As the storm starts to
track away on Saturday, just some lingering rain and snow
showers are expected, but the bulk of the accumulation should be
done by Saturday morning.
Valley areas look to see up to 4 inches of snowfall, with over 6
inches possible for higher terrain areas. We will continue with
the Winter Storm Watch for the southern Adirondacks, northern
Berkshires & southern Vermont. There continues to be a lot of
uncertainty with the forecast due to p-type and snowfall
amounts and our confidence is rather low at this time. Winter
storm warnings and winter weather advisories will likely be
needed for the areas current under a watch and possibility
other parts of the area, including valley areas. Please see our
probabilistic snowfall maps on our website for the full range of
possibilities with this storm.
Long term /Sunday through Wednesday/...
high pressure controls the weather Sunday and then builds east
Monday. Highs Sunday in the mid 40s to around 50 but around 40
higher terrain. Highs Monday in the mid 40s to lower 50s.
Clouds may increase through the day Monday with the approach of the
next system. Rain and mixed precipitation is expected to begin
Monday night as temperatures cool to wet bulb levels. Strengthening
warm advection will turn precipitation to rain during the day
Tuesday. Highs Tuesday in the upper 40s to lower 50s.
Precipitation coverage decreases Tuesday night through Wednesday
but isolated showers/snow showers possible with the gradual exit to
the system and decrease in precipitation coverage. Boundary layer
temperatures may warm as flat upper ridging tries to build east into
our region. Highs Wednesday in the 50s but around 50 higher terrain.
Aviation /12z Thursday through Monday/...
VFR conditions expected through the period ending 06z Friday. High
clouds above 10000 feet will spread through the region through the
day. By this evening, thicker clouds and the leading edge of
precipitation ahead of an approaching area of low pressure are
expected to move into our region. Some snow or mixed precipitation
could be on the door step of all the taf sites around midnight or
shortly after, so including vcsh at that time with ceilings around
Northerly winds at 6 kt or less through the early morning hours.
Winds will be north to northeast and light under 10 knots Thursday
but variable at kpsf and kpou.
Friday: high operational impact. Definite rain...sn...sleet.
Friday night: high operational impact. Definite rain...sn...sleet.
Saturday: moderate operational impact. Likely rain showers...shsn.
Saturday night: no operational impact. No sig weather.
Sunday: no operational impact. No sig weather.
Sunday night: no operational impact. No sig weather.
Monday: no operational impact. No sig weather.
Monday night: moderate operational impact. Chance of rain...sn.
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
Relative humidity values will fall to near 30 percent this afternoon, but
north to northeast winds will only be around 5 mph today.
Precipitation is expected tonight through Saturday morning in
the form of rain, snow and sleet.
the recent rainfall and snowmelt has led to some rises on rivers
and streams, but all streams are now slowly receding. Some
additional snowmelt is expected today, so rivers and streams
will still be running fairly high.
Another storm system is expected on tonight through early
Saturday. Precipitation will be in the form of rain and snow
with some sleet for southern areas. The highest elevations are
expected to see mainly snow or mixed precipitation. This wintry
precipitation will initially prevent much runoff from
occurring. Still, some rivers are expected to have rises by
Friday into Saturday, which will put them near to just below
action stage. Although flooding is not expected through the
weekend, any change in the forecasted precipitation type could
have an impact on river and streams levels. Also, mmefs
suggests that a few river points could approach minor flood
stage during next week if additional precipitation and snowmelt
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
New York...Winter Storm Watch from late tonight through Saturday morning
Massachusetts...Winter Storm Watch from late tonight through Saturday morning
Vermont...Winter Storm Watch from late tonight through Saturday morning