NWS Area Forecast Discussion

FXUS61 KBUF 020011

Area Forecast Discussion
National Weather Service Buffalo NY
711 PM EST Tue Dec 1 2020

Low pressure will remain across southern Quebec through
Wednesday morning before moving away from the region. Snow will
continue across Western NY through Wednesday morning, with
minor accumulations at lower elevations and locally significant
accumulations across the higher terrain east of Lake Erie. East
of Lake Ontario rain will change to snow by late this evening
and continue through Wednesday with greater accumulations
limited to the Tug Hill. High pressure will bring a return to
dry weather later Wednesday through Thursday.


At 7 p.m. a nearly vertically stacked low was centered across
far southern Quebec with a 994 mb surface low. Precipitation
has changed over to snow west of Rochester, with snow mixing in
east of there. Precipitation will continue to change over to
all snow this evening as colder air aloft pours in behind the

IR satellite imagery shows a dry slot pivoting around the low
and moving across the Niagara Frontier early this evening.
However, it also shows deeper moisture just behind a well
defined spoke of vorticity and associated surface trough across
southern Ontario. As a result, precipitation across Western New
York may taper off a bit through around 9 p.m. but should pick
up again as the deeper moisture moves back in. It also will be
colder aloft (about -9c) when this arrives so snow should stick
better. BUFKIT soundings also show this deeper moisture extends
into the dendritic snow growth zone so the snow will be fluffier
with higher liquid to snow ratios.

The heaviest accumulations are still expected to focus across
the higher terrain east of Lake Erie, with the majority of that
accumulation coming from late this afternoon through the pre-
dawn hours Wednesday. Boundary layer flow will become better
aligned from the WNW by this evening after the closed low moves
farther away and shear decreases. This will allow for lake
enhanced upslope flow to increase in efficiency this evening
east of Lake Erie. The strongest upstream connection to Lake
Huron will be found in NE Ohio and NW PA, but mesoscale model
guidance suggests some weaker secondary banding will tie into
the western Southern Tier tonight. Deeper moisture, synoptic
support, and colder air aloft pulls away rapidly Wednesday
morning, so expect the snow to taper off and end during the

Also expect decent snows across the Niagara Frontier tonight,
especially in Niagara and Orleans counties. The main concern
here is that mesoscale guidance suggests Georgian Bay in
addition to enhancement from the trough which should provide
burst of accumulating snows tonight.

East of Lake Ontario, boundary layer flow through most of tonight
remains SW or even SSW, preventing lake enhancement from reaching
the Tug Hill Plateau. Upslope flow will produce some modest
accumulations on the southwest flank of the Tug Hill, with lake
enhancement also producing some minor, slushy accumulations across
Jefferson County. Boundary layer flow veers more westerly on
Wednesday as the low pulls away, with a relatively brief window for
favorable westerly lake enhancement and upslope flow for the Tug
Hill Plateau. Snow totals on the Tug Hill may reach 4-8 inches
tonight through Wednesday, with 1-3 inches for the surrounding lower
elevations of the eastern Lake Ontario region.


Heading into Wednesday night, the closed low from the days prior
will be stacked over southern Quebec, where it will continue to
weaken and advance northward. Meanwhile, upper level ridging over
the northwestern Ohio Valley and its corresponding area of surface
high pressure will advance eastward toward the Atlantic. As these
systems progress along their designated tracks, dry air will filter
in across the region from west to east, acting to diminish the
activity east of Lake Ontario Wednesday night.

With the surface high to the south and the region being on its
northern periphery, dry weather associated with the high will
influence the weather Thursday. Thus, expect a dry day on Thursday.

Setting the scene for Friday`s weather, a shortwave trough will ride
through the northern-stream longwave trough Thursday, producing a
surface low over southern Canada Thursday night. As this surface low
pushes east, it will pivot its associated weak cold front across the
region Friday producing chances for rain/snow showers. Precipitation
type will be dependent on elevation. Additionally with the passage
of the front, temperatures aloft at 850mb will have cooled off
enough to promote some lake enhanced snow showers Friday night for
the area east of Lake Ontario. Outside of an inch or two of snowfall
in the North Country, no notable snow accumulations should occur.


A large scale northern trough over the northeast will remain in
place for most of the long term period. Some better guidance
agreement this afternoon with an east coast storm that will miss
most of the area with just chance POPs for the eastern portion of
the area for Saturday and Saturday night. This storm system will
develop as the southern stream and northern stream phase over the
Tennessee Valley.

A cold front associated with the northern trough will cross the area
on Saturday, but as of now looks mostly dry, will keep slight
chance POPs. With cold air advection behind the frontal passage,
a lake response should begin to set up southeast of the lakes
with a cool northwest flow. Some model spread still with just
how cold 850H temps get, but most guidance gets cold enough to
support a lake response, and combined with lingering synoptic
moisture, and the large trough over the region and shortwave
troughs crossing the region, lake response off of both lakes
should be expected.

Daytime highs mostly in the low 30s over the higher terrain to the
mid and upper 30s for the lower elevations.


Snow and lake enhanced snow will be the main concern for TAFS.
Intensity may wane for a bit through 02Z this evening due to a
mid-level dry slot pivoting around the low. However snowfall
rates will pick up when deeper moisture moves back in later
tonight with widespread IFR or lower at all TAF sites. Expect a
gradual improvement after 09Z or so across W NY TAF sites, with
IFR continuing at KART a few hours longer.

Snow will taper to snow showers during the day Wednesday, with
conditions gradually improving to VFR from W-E Wednesday
afternoon. It will be windy, with gusts to 30 kts.


Thursday...Mainly VFR.
Friday...VFR to MVFR with scattered rain and snow showers.
Saturday and Sunday...MVFR with chance of rain and snow showers.


Low pressure will remain across Southern Quebec through
Wednesday morning before moving away from the region Wednesday
afternoon and night. West winds will increase to around 30 knots
on Lake Erie tonight through Wednesday, and Wednesday through
Wednesday evening on Lake Ontario. There will be gale force
gusts through this period, but sustained winds are generally
expected to peak just below gale force. The winds will produce
high end Small Craft Advisory conditions on both lakes through
Wednesday night, with lower end Small Craft Advisory conditions
then lasting into Friday as the pressure gradient only slowly


NY...Winter Weather Advisory until 7 PM EST Wednesday for
     Winter Weather Advisory until 6 AM EST Wednesday for NYZ001-
     Winter Storm Warning until 1 PM EST Wednesday for NYZ019-020-
     Winter Weather Advisory until 1 PM EST Wednesday for NYZ012.
MARINE...Small Craft Advisory from 7 AM to 10 PM EST Wednesday for
         Small Craft Advisory until 6 PM EST Thursday for LEZ040-
         Small Craft Advisory from 7 AM to 10 PM EST Wednesday
         for LOZ030.
         Small Craft Advisory until 6 PM EST Thursday for



NEAR TERM...Apffel/Hitchcock

NWS BUF Office Area Forecast Discussion