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Area forecast discussion 
National Weather Service Buffalo New York
101 PM EST sun Feb 1 2015

Synopsis...
a storm system organizing in the middle section of the nation will move
into the Ohio Valley tonight then move across Pennsylvania on
Monday. This will produce a wide swath of heavy snow to the north of
the low track tonight through Monday including all of western and
central New York along with very cold temperatures and gusty winds.
The snow will taper off from west to east Monday afternoon. Some
lake effect snow will develop in its wake...especially Tuesday east
of Lake Ontario.

&&

Near term /through Monday/...
the main focus through the near term period continues to be with the
significant synoptic system taking shape over the middle section of the
nation.

Leading edge of snow starting to push into southwest New York this
morning. This area will steadily push northward through the day
today. This process will likely take some time as 12z kbuf and
kaly soundings still rather dry in the middle levels. It will likely
take until middle to late afternoon before the snow reaches the
Niagara Frontier and Rochester. Accumulations through today
continue to look to be on the light side with an inch or two
across the southern tier and an inch or less across the Niagara
Frontier and Rochester.

Temperatures will be steadily falling off through the day today as
colder air filters in from the north with most areas in the teens
by the end of the day...but only single digits across the North
County. Wind chills will be below zero for most areas by the end
of the day.

The real action will be tonight through Monday as the main system
approaches. Strong warm advection and isentropic upglide will
overspread the region from southwest to northeast during the
evening. Specific humidity near the 700mb layer increases to around
3.5g/kg across the western southern tier and around 2.5g/kg from the
Niagara Frontier east to the southern Tug Hill region during the
period of isentropic upglide. The Garcia method would thus suggest
5-8 inches of warm advection snow across the southern tier...and 4-6
inches from the thruway northward. Keep in mind this is just with
the first phase of warm advection forcing with this system.

Following the initial push of warm advection snow...a zone of
stretching deformation and frontogenesis will mature across our
region late tonight through the first half of Monday on the northern
periphery of the 850mb circulation. An examination of time/height
cross sections shows some layers of -epv as well...suggesting some
potential for embedded mesoscale-banding and enhanced snowfall rates
during the warm advection phase and early deformation zone phase.
Expect at least several more inches of accumulation from the
deformation zone through the day.

The final factor will be lake enhancement...which may be significant
along the South Shore of Lake Ontario from Niagara to Wayne counties
including the Rochester area. The lake enhancement will add some
moisture...but more importantly will alter the cloud microphysics
along the South Shore of the lake and result in larger...more fluffy
snowflakes which have a higher snow-water ratio than the rest of the
synoptic environment. This will likely boost accumulations
especially on Monday as the flow becomes better aligned from the
northeast and eventually north.

Putting all of this together...expect a general 8-12 inch
accumulation in most areas with local amounts of 12-15 inches along
the South Shore of Lake Ontario from Niagara to Wayne counties.
There may also be some local amounts exceeding a foot elsewhere if
mesoscale banding does indeed form. The lowest accumulations will be
across Jefferson County...which is just a little far north given the
current storm track...and will also fight dry air in the low levels
which will be supplied by northeast winds out of Quebec. Expect
totals there to range from 4-8 inches.

Northeast winds will produce some blowing and drifting snow in many
areas...but the winds will be strongest by far along the South Shore
of Lake Ontario where gusts of 40-45 miles per hour are possible. This will
produce local whiteouts at times especially within 10-15 miles of
the lake. Temperatures will be very cold through this event...only
in the lower teens or high single numbers in many areas tonight
through Monday. The combination of cold temperatures and winds will
produce wind chills of around 10 below in many areas...and 20-25
below across the Saint Lawrence valley.

&&

Short term /Monday night through Wednesday night/...
the winter storm will shift across the Gulf of Maine to the Gulf of
Saint Lawrence Monday night taking the wrap around synoptic lift and
moisture with it. Expecting synoptic snow showers to quickly taper
off across western New York then central New York overnight leaving
only some weak multi-banded lake effect streamers south of Lake
Ontario. Lake induced equilibrium levels will only run about 5kft
but BUFKIT profiles show just enough moisture and lift beneath the
cap to allow for Shallow Lake snows probably not accumulating more
than an additional inch. Temperatures will fall toward zero or below
overnight with the "warmer" spots remaining under the lake clouds.
Any clearing would allow temperatures to really plummet. Wind speeds of
5-10 miles per hour will push wind chill readings into the negative teens which
may necessitate advisories.

On Tuesday the weak lake effect snow showers south of Lake Ontario look
to lift north toward Watertown and the Saint Lawrence River as the
low level flow backs ahead of a surface trough crossing the central
Great Lakes. This trough will bring a chance of snow area wide by
late in the day Tuesday into Tuesday night. Temperatures Tuesday
will still remain below normal in the teens but will be a rebound
from mondays readings. Southwest flow may actually keep temperatures from
falling much Tuesday night with warm advection ahead of a developing
clipper across the Midwest.

00z models continue to show a clipper low passing across the lower
Great Lakes on Wednesday so have held onto likely probability of precipitation. The clipper
will likely bring a few quick inches of snow as it quickly passes
overhead then east to New England Wednesday night. Wednesday will be
the warmest day of the week as temperatures ahead of the clippers
cold front look to push toward 30 but an Arctic airmass will then
flood across New York in the wake of the cold front pushing
temperatures back into the single digits.

&&

Long term /Thursday through Saturday/...
lake effect snows may briefly return Thursday behind the departing
clipper with cold northwest flow across the lakes. BUFKIT profiles
from the 00z GFS show very limited synoptic moisture and lift
beneath a 8-10kft cap. This would again only allow for limited lake
snow southeast of the lakes. Otherwise cold and dry weather is
expected Thursday and Friday as Arctic high pressure builds over the
Great Lakes. Temperatures will run 10-20 degrees below normal.
Looking out to next weekend 00z European model (ecmwf) shows an Arctic front pushing
south across the Great Lakes while the GFS keeps Saturday dry but
shows a clipper Sunday. Have maintained a low chance for snow on
Saturday.

&&

Aviation /18z Sunday through Friday/...
light snow ahead of a significant system will continue to
overspread the region this afternoon. Once the snow arrives visibility
will drop to IFR...and remain there through the night and much of
Monday. The snow and IFR will be delayed until after about 06z
across the north country including kart. There will be embedded
bands of moderate to occasionally heavy snow with visibility possibly
dropping below airfield minimums at times from middle evening through
Monday morning. Expect ceilings to run MVFR at lower elevations and
IFR across higher terrain during the snow event.

The snow will begin to taper off from west to east during Monday
afternoon with visibility improving but likely remaining IFR much of the
time through late afternoon. Heavier snow may persist longer at kroc
due to lake enhancement off Lake Ontario.

Outlook...
Tuesday...VFR/MVFR with a chance of snow showers and local IFR east
of Lake Ontario.
Wednesday...MVFR/IFR with snow likely.
Thursday...MVFR with a chance of snow showers.

&&

Marine...
northeast winds will increase today as low pressure organizes and
moves into the lower Ohio Valley...with high pressure remaining in
place over Quebec. The pressure gradient between the approaching low
and strong high pressure over southeast Canada will force northeast
winds to increase further later tonight into the first half of
Monday. This will produce low end gales on Lake Ontario. Winds will
begin to diminish and become more northerly Monday afternoon as the
low pulls off the southern New England coast and the pressure
gradient relaxes.

Heavy freezing spray will be likely on Lake Ontario tonight through
Monday morning.

&&

Buf watches/warnings/advisories...
New York...Winter Storm Warning until 4 PM EST Monday for nyz010>014-
019>021-085.
Winter Weather Advisory from 1 am to 7 PM EST Monday for
nyz007.
Winter Storm Warning from 10 PM this evening to 7 PM EST
Monday for nyz005-006-008.
Winter Storm Warning from 4 PM this afternoon to 7 PM EST
Monday for nyz001>004.
Marine...heavy freezing spray warning from 8 PM this evening to 7 PM
EST Monday for loz042>045-062>065.
Gale Warning from 11 PM this evening to 1 PM EST Monday
for loz042>044-062>065.
Small Craft Advisory from 11 PM this evening to 4 PM EST
Monday for loz045.

&&

$$

Synopsis...Hitchcock/tma
near term...Hitchcock/tma
short term...Smith
long term...Smith
aviation...Hitchcock/tma
marine...Hitchcock/tma

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