Scientific Forecaster Discussion
fxus61 kaly 181451
Area forecast discussion
National Weather Service Albany New York
951 am EST Mon Feb 18 2019
low pressure will redevelop south of Long Island today,
bringing periods of snow across the area and some areas of freezing
drizzle from the capital region south. The snow will taper to
scattered snow showers and flurries by late this afternoon into the
early evening. High pressure will bring mainly dry and seasonably
cold temperatures tonight through Tuesday night before another storm
system arrives late Wednesday into Thursday.
Near term /until 6 PM this evening/...
Winter Weather Advisory remains in effect through 4 PM EST
this afternoon for the Mohawk Valley, greater capital region,
helderbergs, Mid Hudson valley, Taconics, eastern Catskills,
Berkshires and Litchfield County, Connecticut...
As of 950 am EST...the secondary sfc low continues to form
south of Long Island this morning with the primary sfc low
weakening over central New York and northern PA. A mid-level short-
wave trough is moving towards the region from the eastern Great
Lakes region. The kenx and regional mosaic radars continue to
show snow, mainly light in intensity filling in just north and
west of the capita region into the western-central Mohawk and
Adirondacks. This snow is increasing due to the convergence with
the inverted sfc trough setting up northwest of the secondary
coastal wave, and the differential cyclonic vorticity advection
with the short- wave. We are also seeing some enhanced low-level
fgen with the inverted trough.
Further south, we have had reports of freezing
drizzle in the Mid Hudson valley, southeast Catskills, and even
as far north as the capital region. The lack of ice nuclei in
the clouds briefly this morning has allowed for the patchy to
areas of freezing drizzle in the dry slot. Some of the pcpn
changes back over to snow in the Mid Hudson valley, when the
pcpn increases in intensity. We added a few tenths of an inch of
snow to the Mid Hudson valley to account for this.
We do not plan on ending any headlines with an additional 1-2"
and some isolated 3" amounts from the capital region/Berkshires
north and west. Further south, a light glaze is possible and
light snow accums of a coating to maybe a half an inch. Temps
have been slow to rise from the teens to 20s. We could still see
some lower to mid 30s from just south of Albany down into the
Mid Hudson valley. Expect 20s north and west. As the wave,
pulls east of Cape Cod in the mid to late afternoon, we will
have to monitor for persistent convergent snow band or upslope
snow with the inverted trough that may impact the northern and
central Taconics, southern VT, the helderbergs and the capital
region with additional light snow accums. The latest 3-km NAM
and hrrr show the potential for some Mohawk Hudson convergence
snow/snow showers based on the low-level wind fields down the
Mohawk and Hudson River valleys. We will watch the trends to
see if this materializes between 20z to 00z /3-7 PM/.
Previous near term...
As of 630 am EST, earlier bandlets of light snow have lifted
northward, affecting mainly the southern Adirondacks, with only
spotty light snow/snow grains farther south and east. We expect
a relative lull in overall precipitation intensity over the next
1-2 hours, before a slight uptick develops once again across the
SW Adirondacks and western Mohawk Valley, as increasing DPVA
associated with the mid level trough axis spreads east and
south. This should allow snow to increase once again in these
areas first, then expanding east across the Lake George/Saratoga
region and southern VT, and perhaps south into portions of the
capital region during the mid to late morning hours.
So, best forcing through this morning appears to be mainly
north of the I-90 corridor, across the Mohawk Valley, southern
Adirondacks, Lake George/Saratoga region into southern Vermont. In
these areas, an additional 1-2 inches of snow is expected
today, mainly this morning, with locally higher amounts possible
across the Adirondacks. To the south and east, snow should be
more intermittent, with additional accumulation of less than one
inch across the Mid Hudson valley, southeast Catskills, Litchfield
County and southern Berkshires, with perhaps around an inch
closer to the capital region and northern Berkshires.
Snow should taper to snow showers from northwest to southeast later this
afternoon as the mid level trough axis shifts south and east.
Some mesoscale models suggest a small area/band of snow may
persist and/or intensify late this afternoon across portions of
the capital region, eastern Mohawk Valley and helderbergs, in
association with low level confluent flow. Trends will need to
be watched for this additional development, which could produce
an additional 1-2 inches of snow in isolated areas where any
such areas or bands of snow persist.
Temps are tricky today, as low level cold air continues to
settle southward down the Hudson River valley, at the same time
a remnant occluded front attempts to brush southern and central
areas. Have undercut most guidance for high temps today, and
perhaps not by enough, with forecast highs only in the lower/mid
20s across the southern Adirondacks, Lake George/Saratoga
region, Mohawk Valley and southern VT, with mid/upper 20s
closer to the capital region and Berkshires, and lower/mid 30s
across the Mid Hudson valley and lower elevations of northwest CT.
However, there is a possibility that temps do not rise much at
all for many areas, remaining in the upper teens to mid 20s,
especially northern portions of the Hudson Valley.
Short term /6 PM this evening through Wednesday/...
tonight, snow showers/flurries may linger across portions of the
capital region, northeast Catskills and Berkshires within
aforementioned remnant low level confluent flow. These should
taper off toward and after midnight, with clearing occurring.
With a fresh snowpack in place, and clearing skies, temps may
drop off rapidly late tonight in some areas, particularly across
the southern Adirondacks, where subzero mins are forecast.
Elsewhere, expect widespread single digits and lower teens by
Tuesday-Tuesday night, mainly clear skies are expected, with the
exception of some lake effect clouds across portions of the
eastern Catskills Tuesday, and the western Mohawk Valley and
southwest Adirondacks Tuesday evening. Some flurries could even
occur in some of these areas, as low level winds back more into
the west and southwest. Otherwise, expect cold temps Tuesday
with highs mainly in the teens and 20s, with another very cold
Tuesday night expected, with lows ranging from zero to 10 below
across the southern Adirondacks, with single digits and teens
Wednesday, the next storm system will approach from the
southwest later in the day. After some morning sunshine, expect
increasing clouds, with light snow developing by late afternoon
from southwest to northeast. Some minor accumulations will be
possible by sunset, especially central and southern areas. Highs
mainly in the 20s to lower 30s.
Long term /Wednesday night through Sunday/...
flat upper ridging across eastern North America is expected to
contribute to the weakening and deamplification of upper systems
that track out of the central U.S. And Canada. There should also be
a lack of deep moisture along with the weakening upper dynamics and
relatively weak low level forcing.
One system is timed to affect our region Wednesday night and
Thursday with warm advection increasing through Wednesday night.
Isentropic lift increases as well and snow gradually transitioning
through mixed precipitation is expected Wednesday night into
Thursday morning. There could be some light sleet and freezing rain
in some areas, too. During the day Thursday, temperatures should
warm well above freezing so that precipitation becomes mainly rain.
Highs Thursday in the 40s but near 50 southern areas and mid to
upper 30s northern areas.
The system departs through the day and evening of Thursday and a dry
and quiet weather period is expected through Saturday. Although,
another system will be approaching and timing is very uncertain,
some clouds and leading area of scattered showers could be in our
areas by later Saturday.
Highs Friday in the upper 30s to lower 40s but lower 30s northern
areas. Highs Saturday in the lower to mid 40s but mid 30s northern
areas. Decent consensus in long range guidance/ensembles for the
next system to track through the northern periphery of the upper
ridging and bring precipitation into our region Saturday night and
Sunday. Highs Sunday well into the 40s but some upper 30s northern
Aviation /15z Monday through Friday/...
periods of light snow will affect the taf sites through about 20z-
22z. There could be some patchy freezing drizzle at kpou this
morning. Ceilings will vary between 1500-3000 feet with the ceilings
below 3000 feet during brief intervals of near moderate snow. So,
including MVFR ceilings and visibilities ending this afternoon.
There could be a brief period of modified/hybrid Mohawk Hudson
convergence between 20z-24z at kalb and including a prob30 for IFR
visibilities and borderline IFR ceilings because mesoscale models
are increasingly showing hints of that localized feature.
Once all snow ends, ceilings and visibilities will be VFR, late this
afternoon through this evening.
Light north to northeast winds this morning will become north to
northwest around midday and then increase to 10-15 kt with gusts 20-
25 kt through this afternoon. Northwest winds diminish to less than
10 kt this evening.
Tuesday night: no operational impact. No sig weather.
Wednesday: moderate operational impact. Chance of snow.
Wednesday night: high operational impact. Likely snow...sleet.
Thursday: moderate operational impact. Chance of rain showers...ra.
Thursday night: no operational impact. No sig weather.
Friday: no operational impact. No sig weather.
light to moderate snow will taper off later today into this
Another seasonably cold and dry stretch is likely tonight
through most of the day Wednesday. Some thickening of ice is
possible on the main Stem rivers, lakes and streams.
Another storm system is expected late Wednesday into Thursday
and this storm will bring snow changing to a wintry mix and/or
rain to the region. As of right now, about a quarter to half
inch of liquid equivalent is expected.
Drier weather looks to return late in the week with slightly
above normal temps, but overnight lows should fall below
freezing with any snow melt refreezing.
As a result, river and stream levels will generally hold steady
through the end of next week and widespread snow melt, ice
movement or flooding is not expected at this time.
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
CT...Winter Weather Advisory until 4 PM EST this afternoon for
New York...Winter Weather Advisory until 4 PM EST this afternoon for
Massachusetts...Winter Weather Advisory until 4 PM EST this afternoon for