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Major Lake Effect Snowstorm: Nov 29-Dec 4th


BuffaloWeather
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Looks to be a long lasting major lake effect snow event with multiple feet of snow expected. Hardest hit areas will be south of Buffalo. The top analogs are really impressive.

...LAKE EFFECT SNOW WARNING IN EFFECT FROM 7 AM FRIDAY TO 7 PM EST MONDAY... * WHAT...Heavy lake effect snow expected. Multiple feet of snow will be possible through the weekend in the most persistent lake snows. Snowfall rates will average one to two inches an hour, but higher rates will be possible.

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.SHORT TERM /FRIDAY THROUGH SUNDAY NIGHT/...
...Long-Duration, High-Impact Lake Snows Expected Friday Through the
Rest of the Weekend...

During this period the axis of deep upper level troughing will
slowly pivot from James Bay and the central Great Lakes to New
England and the Canadian Maritimes...while circulating a deep
cyclonic flow of progressively colder air that will result in 850 mb
temperatures lowering from around -8C/-9C Friday to the -10C/12C
range Saturday and Sunday. Coupled with sufficient background
moisture and the approach/passage of some shortwaves/surface troughs
embedded within the deeper larger-scale circulation (the most
notable of which looks to come between Sunday and Sunday evening)...
this will result in an environment rather favorable for long-
duration heavy lake effect snows downwind of the lakes. A
predominantly westerly flow will direct the heaviest overall snows
across areas east of the lakes...where multiple feet of snow are
expected and where Winter Storm Watches have therefore been upgraded
to Lake Effect Snow Warnings. This being said...the aforementioned
shortwave/surface trough passages may also induce some periods of
west-southwesterly flow at times...most notably east of Lake Ontario
on Friday...and again downwind of both lakes Saturday into Sunday.


Digging a bit further into the forecast details...during the day
Friday a better aligned flow and marginally colder airmass will
support the best lake effect snows east of Lake Erie...with these
gradually becoming better organized and slowly drifting north across
Chautauqua/Cattaraugus and Southern Erie/Wyoming counties as
synoptic moisture increases a bit and the flow backs a little across
the lake...with northern portions of the band possibly making it as
far north as some of the more distant Buffalo Southtowns during the
afternoon. Inland from the lakeshore and where snow is most
persistent...this band could produce as much as 5 to 10 inches by
the end of the day. Meanwhile off of Lake Ontario...a bit more of a
backed/sheared west-southwesterly flow and slightly warmer airmass
out ahead of a weak surface trough passing across southern Quebec
will result in more disorganized lake effect snows east-northeast of
that lake...where 2 to 4 inches will be possible inland from the
lakeshore.

As we move into Friday night...winds will veer a bit to more of a
due westerly orientation following the departure of the above
mentioned surface trough...resulting in the lake snows settling back
southward across the traditional snow belts east of both lakes...
including the Tug Hill region east of Lake Ontario. Further gradual
cooling of our airmass and an increase in orographically-driven lift
coupled with an increase in fetch will allow the Lake Ontario lake
snows to really get going as these drift toward the Tug Hill
region...likely resulting in fresh accumulations of over a foot from
areas just south of Watertown to the northern portions of the Tug
Hill. Meanwhile off of Lake Erie...another general 5 to 10 inches of
accumulations will be likely within the most persistent snows from
the southern third of Erie county southward into Chautauqua and
Cattaraugus counties.

As we move through Saturday and Saturday night...the low level flow
will again back at least somewhat out ahead of a more significant
shortwave impulse/surface trough approaching from the Upper Great
Lakes. This being said...there remains a great deal of uncertainty
at this time with respect to exactly how much winds will back...with
the 12z guidance exhibiting a range of scenarios between just a
little north of due west (the NAM) to more southwesterly (the
GEM)...with the GFS lying roughly in between the middle of these two
extremes.

Off Lake Erie...this stark difference is rather significant in that
it implies a number of possible scenarios ranging from the lake
snows remaining entirely within the current Lake Effect Snow Warning
area (and south of the Buffalo area)...to making a northward
migration all the way to the city and central/northern suburbs.
Additionally...there are also notable differences in the timing of
this wind shift...as well as other factors such as a possible
increase in shear that further complicate the forecast for this time
period. While definitely not a high confidence forecast...given the
holiday weekend and the increased potential for at least some of the
heavier lake snows to make it far enough north to potentially impact
portions of the Buffalo area (most likely South Buffalo and the more
immediate Buffalo Southtowns) for at least a portion of this time
frame...out of an abundance of caution we have hoisted an additional
Winter Storm Watch for Northern Erie county from Saturday through
Sunday (more on Sunday in a moment). At this point...between
Saturday and Saturday night roughly from 6 to 12 inches of snow
appear possible where the Lake Erie snows are most persistent...
though it must be emphasized that actual amounts will be highly
dependent upon both band movement/residence time and the amount of
available shear...factors that could result in higher or lower
amounts than currently forecast.

Meanwhile off Lake Ontario...a stronger/more organized band of lake
effect snow should be poised to dump an additional foot or more of
snow roughly every 12 hours or so as it wobbles back northward to
the Watertown area between Saturday and Saturday night...with exact
amounts that will be received again a direct function of band
movement/residence time and the amount of shear. At this point would
expect somewhat heavier snows during Saturday when the flow is more
westerly and less sheared...with a shorter west-southwesterly to
southwesterly fetch and increased shear likely inducing at least
some weakening in the snow band Saturday night.

Sunday and Sunday night...the aforementioned more significant
shortwave impulse/surface trough will slide southeastward and across
our area. The increase in lift and moisture attendant to this
feature should help to at least temporarily reinvigorate the lake
snows while also driving these back southward...first to areas east
of the lakes...and then eventually southeast of the lakes as the
flow veers to west-northwesterly to northwesterly. Additional
significant accumulations are likely through this time...with these
again highly dependent upon band residence time and strength...
factors that will in turn be heavily dependent upon the timing and
speed of the trough passage. Given the potential for additional
significant accums and the forecast uncertainty due to the above
factors...the new Winter Storm Watch for lake effect snow for
Northern Erie county extends out through Sunday and the first half
of Sunday night.

Outside of the main lake effect bands...it will be mainly dry with
just some much more scattered snow (and during Friday, rain) showers
for much of this period...save for during Sunday/Sunday night when
the aforementioned trough passage may also bring some more general
scattered to numerous show showers/minor accumulations. Otherwise
temperatures will average below normal...with highs pulling
back to the upper 20s to mid 30s for both Saturday and Sunday.

&&

.LONG TERM /MONDAY THROUGH WEDNESDAY/...
An upper level low will remain over eastern Canada and the Great
Lakes region this period, with cold air (850 hPa temperatures -9 to -
12C) flowing over the still warm lake waters generating lake snows
downwind of Lakes Erie and Ontario. A shortwave passing through the
flow may lift the snowbands northward towards Buffalo and Watertown
Tuesday-Tuesday night; otherwise west to west-northwest flow will
continue.
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The plume of increasingly focused lake snow should be fairly stationary between Watertown and the northern slopes of the Tug and the Watertown metro area Friday night. The quality of boundary layer moisture and instability strongly suggest this band will become quite intense at times with 3+ inch/hour snowfall rates possible. In addition...the first 36 to 48 hours of this event (off both lakes) will feature a nearly PERFECT environment for lake effect thundersnow. A fairly deep mixed phase layer (in this case -10c level arnd 4kft) will be in place with an equilibrium level near or greater than 15kft. Given the strong convergence in the low levels... we can fully anticipate thunder/lightning to be found within the heart of each band...particularly within 20-25 miles of the source of the instability...the lakes.

Tug/Watertown area is going to get some crazy stuff with this one. Excerpt from BUF AFD.

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1 hour ago, andyhb said:

Tug/Watertown area is going to get some crazy stuff with this one. Excerpt from BUF AFD.

The entire thing is drool worthy, especially off Ontario

.NEAR TERM /THROUGH FRIDAY NIGHT/...
While there will be a lull in the weather early this evening...
deepening cold air (H85 temps arnd -10c) in the wake of the exited
storm system will combine with a fresh lobe of deep synoptic
moisture to set the stage for the start of the much advertised lake
effect snow event. A westerly flow of the cold air will encourage
disorganized lake effect rain and snow to start over Chautauqua
county during the evening hours. This lake induced convection will
try to become better organized during the wee hours of Friday
morning when there could even be a little thunder and lightning with
the consolidating band. As is typically the case...the same will
take place east of Lake Ontario some 3-6 hours later. Fresh snowfall
amounts by daybreak will generally range from 1 to 3 inches across
southern Chautauqua county and also over the Tug Hill plateau.

As we push through Friday and Friday night...a highly amplified
longwave pattern over North America will deliver the coldest airmass
of the season so far...and this will support the start of what
should turn out to be a classic and highly impactful lake effect
snow event. Lake temperatures are near record warm after the warm
fall season and will support extreme instability over the lakes
through the event with lake induced equilibrium levels in the 15-20K
foot range. The strong instability will very likely support
thundersnow in the stronger bands.

Expect peak snowfall rates of 2-3" per hour at times when the bands
are at their strongest. West to WSW winds will gust to 25-35 mph at
times. This will produce some typical blowing and drifting in open
areas.

Off Lake Erie...

Lake effect snow will already be in place across Chautauqua county
early Friday morning on westerly flow with bands of moderate to
heavy snow that will become better organized as it will lift north
during the course of the day. For the midday and afternoon...a
resulting plume of moderate to heavy snow will extend from
northern Chautauqua and southern Erie counties across Wyoming county.
Daytime snow accumulations will range from 5 to 10 inches within
this lake effect plume with the higher amounts being found on the
Chautauqua ridge.

The band will continue to become better organized Friday night while
remaining in place from the Chautauqua county lakeshore across
southern Erie county to Wyoming county. Snowfall rates of 1 to 3
inches an hour will be likely within the heart of this band with
overnight snowfall forecast to range form a few inches across
western Wyoming county to 8 to 14 inches from near Silver Creek
across southern Erie county.

Off Lake Ontario...

Lake effect snow will be in the process of organizing and
intensifying east of the lake early Friday morning. Westerly flow
early will back to the WSW during the day, carrying a band of snow
from the central and northern Tug Hill northward towards Watertown
during the afternoon.

The plume of increasingly focused lake snow should be fairly
stationary between Watertown and the northern slopes of the Tug and
the Watertown metro area Friday night. The quality of boundary layer
moisture and instability strongly suggest this band will become
quite intense at times with 3+ inch/hour snowfall rates possible.

In addition...the first 36 to 48 hours of this event (off both
lakes) will feature a nearly PERFECT environment for lake effect
thundersnow. A fairly deep mixed phase layer (in this case -10c
level arnd 4kft) will be in place with an equilibrium level near or
greater than 15kft. Given the strong convergence in the low
levels... we can fully anticipate thunder/lightning to be found
within the heart of each band...particularly within 20-25 miles of
the source of the instability...the lakes.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
...LONG DURATION, HIGH IMPACT LAKE EFFECT SNOW TO CONTINUE THROUGH
THE WEEKEND...

The longwave pattern across North America will amplify over the
weekend, with a ridge building along the US/Canadian Pacific Coast,
forcing a longwave trough to deepen over central and eastern North
America. This will deliver the coldest airmass of the season so far,
with the synoptic setting prime for a long duration, significant
lake effect snow event downwind of Lake Erie and Lake Ontario. Lake
temperatures are near record warm levels after the warm fall season,
and will support extreme instability over the lakes with lake
induced equilibrium levels generally in the 15-20K foot range much
of the time...and even a bit higher than that at times east of Lake
Ontario. Coupled with a fairly deep mixed phase layer (in this case
-10c level around 4kft) and strong low level convergence...this
degree of instability may also support some thundersnow in the
stronger bands...particularly east of Lake Ontario where the most
intense lake snows are expected.

A mid level closed low will continue to wobble about near James Bay
through the first part of Saturday, in the classic position for a
significant west to west-southwest flow event...with local pattern
and CIPS analogs both suggesting a major, high impact lake effect
snow event east of the lakes. After that time...the mid level closed
low will elongate and break into two parts...with the larger and
more dominant eastern portion breaking off towards Labrador...and
the western portion and its embedded shortwave pivoting southeast
across the central/eastern Great Lakes Saturday night and Sunday.
This will induce changes in the low/mid level flow pattern such that
winds will turn more northwesterly by Sunday night and Monday...
thereby directing the lake snows to areas southeast of the lakes.

When the bands are at their strongest...peak snowfall rates may
reach 1-3" per hour at times east of Lake Erie...and to as high as
4+" per hour east of Lake Ontario. Westerly to west-southwesterly
winds will also gust to 25-30 mph at times (most likely on
Saturday)...leading to the typical blowing and drifting in open
areas. With all that said...let`s dig a little deeper into the
forecast details.

Off Lake Erie...

On Saturday, flow adjustments out ahead of the slowly approaching
synoptic-scale trough axis and the effects of lake aggregate
troughing will likely allow boundary layer flow to back to the west-
southwest...carrying the band of lake effect snow northward through
Erie County into the more immediate Buffalo Southtowns. There still
remains some uncertainty with how far north the band will get, with
the Canadian GEM still the farthest north amongst the guidance.
Early season lake effect snow events with strong instability often
end up farther north than much of the guidance, and with this in
mind have nudged the band position yet a little further northward...
with the latest forecast lying north of the ensemble mean and
closest to the Canadian GEM position.

Expect the band to reach its northernmost position sometime between
Saturday afternoon and Saturday evening. There will be a very sharp
cutoff to accumulating snow on the northern edge, as is often the
case in this type of setup. Expect further adjustments to band
position and intensity in the coming days as the details become more
clear.

On Sunday, boundary layer flow may still be west-southwesterly for
the first half of the day, with a band possibly still over or near
the Buffalo Southtowns. The aforementioned shortwave and attendant
surface trough will then cross the eastern Great Lakes during the
afternoon and early evening hours. Model soundings suggest that
shear may increase over Lake Erie ahead of the shortwave/surface
trough, which may allow for some weakening and broadening of the
band. Later Sunday afternoon and Sunday night, boundary layer flow
will rapidly veer to the northwest behind the trough, carrying the
lake effect snow quickly southward into the western Southern
Tier...where it will then remain through the rest of the period.

Taking expected snowfall totals in the near term period also into
account...expect storm totals through the end of the Short Term
period to reach multiple feet in the most persistent bands. More
precise storm totals will ultimately depend on how long the band can
remain over one particular area, with more clarity in the coming
days as the fine details of the forecast become more certain. This
being said...at this point expect the highest totals across western
Chautauqua, far northwest Cattaraugus, and southern/central Erie
County.

Off Lake Ontario...

Saturday through Sunday expect the band to oscillate between
Watertown and the northern Tug Hill region numerous times owing to
subtle changes in the boundary layer flow direction. The quality of
boundary layer moisture and instability suggest this band will
likely become quite intense at times, with 4+ inch/hour snowfall
rates and thundersnow possible at times.

The band will remain in the same general area of the northern Tug
Hill or near Watertown through most of Sunday. The mid-level
shortwave will then cross the eastern end of Lake Ontario Sunday
evening, with its associated surface trough crossing the lake and
merging with the lake effect band...resulting in the latter getting
carried quickly southward across the Tug Hill and into the Wayne-
Northern Cayuga-Oswego County corridor overnight.

Taking expected snowfall totals in the near term period also into
account...expect storm totals east of Lake Ontario to also reach
multiple feet in the most persistent bands...and to be higher than
those east of Lake Erie. More precise storm totals will ultimately
depend on how long the band can remain over one particular area,
with more clarity in the coming days as the fine details of the
forecast become more certain. This being said...as of now expect the
highest totals across the northern Tug Hill region to near, or just
southeast of Watertown.
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Hey folks, I mostly post in the tennessee valley thread, been a member here for years.  Car load of guys loading up to head to bills game from Tennessee, we are trying to swing east and enter buffalo from geneova-batavia angle.  We have an all wheel drive vehicle.  Do we have a prayer ha?  I am guessing the 3.4 inches falling in Batavia over 3 days is nothing to you guys, and the roads will be solid.  Buffalo city center seems mildly hit with things rapidily getting worse to the south.  Thanks for any thoughts you may have.

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4 minutes ago, Bigbald said:

Hey folks, I mostly post in the tennessee valley thread, been a member here for years.  Car load of guys loading up to head to bills game from Tennessee, we are trying to swing east and enter buffalo from geneova-batavia angle.  We have an all wheel drive vehicle.  Do we have a prayer ha?  I am guessing the 3.4 inches falling in Batavia over 3 days is nothing to you guys, and the roads will be solid.  Buffalo city center seems mildly hit with things rapidily getting worse to the south.  Thanks for any thoughts you may have.

Youll be fine if you go around the band. You'll likely be fine if you drive up the I90 thruway as they usually plow that first but conditions will be rough. Good call to go around the band. I'll be at the game too!

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6 minutes ago, BuffaloWeather said:

Youll be fine if you go around the band. You'll likely be fine if you drive up the I90 thruway as they usually plow that first but conditions will be rough. Good call to go around the band. I'll be at the game too!

Thanks, we are heading up to Pittsburg tomorrow, swinging east from there.  Hope to backdoor into buffalo midday Saturday.  No way in heck we are driving to the game as we will Uber or whatever the best method is to get to the stadium (staying in downtown).  Seeing a bills game in lake effect snow is a bucket lister!

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