Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 240027
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
727 PM EST Sat Feb 23 2019

.SYNOPSIS...
A strong storm system will track across the central Great Lakes and
southern Canada tonight and Sunday. This system will spread rain
showers across our area tonight, with its powerful trailing cold
front then crossing the area on Sunday and ushering in an extended
period of widespread damaging winds that will last through Sunday
night. Meanwhile, colder air behind the front will result in lake
effect snow and significant blowing snow east of the lakes late
Sunday through early Monday, with blizzard conditions likely across
the Tug Hill region.

&&

.NEAR TERM /THROUGH SUNDAY NIGHT/...
Deepening low pressure over Missouri will track northeastward to
near the SOO Sunday morning...before continuing on to western Quebec
by Sunday evening...where its pressure will bottom out around 970mb.
Its trailing powerful cold front will enter Western NY around late
Sunday morning, then will reach the eastern Lake Ontario region by
mid to late afternoon. A very strong and deepening surface low
taking such a track to the north and west of our area is the perfect
recipe for high impact weather across our region, including damaging
winds, lakeshore flooding, and eventually lake effect snow.

WINDS...

Ahead of the main wind event, a strong southerly low level jet of
60+ knots will cross the region late tonight and Sunday morning. A
steep low level inversion based near the ridge tops will allow for
ducting of some of these strong winds down the lee slopes of the
Chautauqua Ridge, producing downslope wind gusts of around 50 mph
along the Lake Erie shore of Chautauqua and Southern Erie counties.
A wind advisory is in effect to cover this potential.

The main wind event will begin with the passage of a strong cold
front, which reaches Western NY by late morning or midday Sunday,
and then reaches the eastern Lake Ontario region by mid to late
afternoon. Strong southwest winds will begin rapidly with the
passage of the surface cold front. Winds aloft in the 2-5K foot
layer peak in the 70-80 knot range, depending on model of choice,
with the higher resolution NAM based guidance the strongest on winds
aloft. Strong cold advection behind the cold front will support a
period of strong post-frontal subsidence, and also steepen lapse
rates in the boundary layer sufficiently for efficient mixing of
higher momentum from aloft. The 1.5 PVU surface is forecast to
descend to below 500mb along the leading edge of the trough,
suggesting a tropopause fold and intrusion of stratospheric air into
the troposphere, a classic signature for steepening lapse rates
during high wind events.

Model guidance has been incredibly consistent on this event over the
past 4-5 days, and continues to result in a high confidence forecast
for high impact wind gusts. Peak wind gusts are likely to reach 75
mph on the lake plains northeast of the lakes. This includes the
Lake Erie shore extending northeast across the Niagara Frontier to
Rochester, and also in Jefferson County northeast of Lake Ontario.
Winds will not be quite as strong farther inland away from the lake
plains, but still easily warning criteria with peak gusts of up to
65 mph across the higher terrain of the interior Southern Tier,
western Finger Lakes, and points southeast of Lake Ontario to Lewis
County. The strongest winds on the lake plains will be Sunday
afternoon when wind direction is WSW. The strongest winds from the
interior Southern Tier to the western Finger Lakes and southeast of
Lake Ontario will be Sunday night when winds become due westerly.

Winds of this magnitude will produce widespread power outages that
may last for days, along with extensive tree and powerline damage.
Property damage to shingles and siding is likely, and buildings
under construction and older buildings that are starting to
deteriorate may experience significant damage.

RAIN...

The initial shot of warm air advection attendant to the approaching
storm system has resulted in the development of some spotty light
showers and sprinkles across areas south of Lake Ontario early this
evening...with the bulk of this in the form of the latter and also
likely not making it to the ground.

With respect to temperatures...most of the area is already above
freezing. Exceptions to this are some isolated pockets of around-
freezing readings across far interior portions of the Southern
Tier...with somewhat larger areas of freezing or sub-freezing
temps across portions of the North Country - where some temporary
clearing allowed for corresponding brief cooling following sunset.
At this point...still expect readings across the North Country to
slowly rise and be above freezing by the time any light showers
arrive later on this evening...though these will need to be watched
closely to make sure that this happens. If not...a short-fused
winter weather advisory might need to be issued.

Another stronger push of warm advection and isentropic upglide,
along with DPVA ahead of the strong trough, will spread across the
eastern Great Lakes late tonight and continue through early Sunday
morning. This will produce more widespread rain showers across the
region, with rainfall amounts of a tenth to a quarter of an inch
common.

The warm advection rain will quickly end from southwest to northeast
Sunday morning. There will likely be another narrow band of rain
showers right along the surface cold front later in the day.

TEMPERATURES...

The temperature trend over the next 36 hours will be decidedly non-
diurnal. Temperatures tonight will rise steadily in a strong warm
advection regime ahead of the system. Temperatures will start this
evening in the 30s, then rise well into the 40s by late tonight.
Highs will occur Sunday morning just ahead of the cold front,
reaching at least the mid to upper 50s in most areas. A few 60
degree readings cannot be ruled out in downslope areas on the lake
plains. Behind the cold front, temperatures will nose dive in the
afternoon, reaching the lower 30s by early evening across Western NY
and upper 30s across central NY and east of Lake Ontario. Lows
Sunday night will be in the low to mid 20s in most areas.

LAKE EFFECT SNOW...

Strong cold advection behind the system will allow lake induced
equilibrium levels to rise to around 8K feet over Lake Erie and 10K
feet over Lake Ontario Sunday night. Ample synoptic scale moisture
will be found in the wrap around regime of the system as the main
mid level trough crosses the region.

Off Lake Ontario...

Temperatures aloft will get cold enough to support a lake response
by early Sunday evening. Initial WSW boundary layer flow will focus
the early part of the event across Jefferson County and the northern
Tug Hill. Boundary layer flow will veer westerly overnight into
early Monday morning, focusing the majority of the intensifying lake
response on the Tug Hill. Upslope flow will play an important role
in enhancing snowfall amounts, with true warning criteria snow
likely confined to the higher terrain of the Tug Hill Plateau.

The very strong winds will be a much bigger concern than actual
snowfall amounts. Winds gusting to over 60 mph Sunday night will
likely produce blizzard conditions in and near lake effect snow
bands and in the upslope zone of the Tug Hill Plateau. The only
question is whether the lake effect bands can be persistent enough
in any one area to produce blizzard conditions for 3 or more
continuous hours, which is part of the criteria. The upslope flow into
the Tug Hill should keep the snow fairly persistent across the
higher terrain even if the pure lake effect snow bands are being
fractured by the strong winds. With this in mind, the Winter Storm
Watch east of Lake Ontario has been upgraded to a Blizzard Warning.
The worst conditions will focus on the Tug Hill region, including
southern Jefferson, northern Oswego, and western Lewis counties.

Off Lake Erie...

The lake currently has extensive ice cover, but the very strong
winds will likely result in the fracturing of the ice field with
plenty of openings developing. In addition, conditions are favorable
for an upstream connection to Lake Michigan banding, along with some
enhancement from synoptic scale convergence near the base of the mid
level trough. The snow amounts will be contingent on the idea that
breaks will develop in the ice field, but that seems like a
reasonable assumption given the strength of the wind event.

The airmass will become cold enough to support a lake response by
mid to late afternoon Sunday. Boundary layer flow is initially WSW,
which will bring some snow to most of Erie, Genesee, and Wyoming
counties. When there is ice on the lake, lake effect snow often
develops farther north than one would expect for a given wind
direction, because an opening in the ice will often develop ENE of
Long Point. Overnight Sunday night boundary layer flow will veer
more westerly, carrying the lake effect snow showers into Southern
Erie, Wyoming counties and the western Southern Tier.

Snowfall amounts may reach 1-3 inches in parts of Northern Erie and
Genesee counties, with 3-5 inches across the higher terrain well
south of Buffalo and Batavia into the Chautauqua Ridge. The snow
amounts are not the issue however, significant blowing and drifting
snow will be the main concern. With this in mind, a Winter Weather
Advisory has been issued for late Sunday through early Monday for
the blowing snow. Conditions may approach blizzard at times, but the
weaker lake response will likely not allow these conditions to last
for very long at any given location.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
Behind the intense surface low that will quickly be moving northeast
into the Gulf of St Lawrence, cold air advection will continue to
spread across the region.  The coldest airmass aloft (using 500mb as
a proxy) will be over Western NY during the morning and heading
toward the Eastern Lake Ontario region.  The well mixed and
saturated airmass, together with steep lapse rates supporting lake
effect snow will result in continued blizzard conditions east and
southeast of Lake Ontario.  Expect winds to continue to gust up to
65 mph in the morning together with blowing snow.  This will make
any travel north of Syracuse to south of Watertown extremely
hazardous (ex I-81).  Snow amounts, what can be measured, will be on
the order of 2-4", but impacts will mostly be from near zero
visibility and drifting rather than from accumulation.

Once the upper level cold pool moves past Monday night, expect lake
snows to slowly wind down while the band drifts a little further
west along the Southern Lake Ontario shoreline.  Blizzard conditions
should no longer be an issue by this time and winds continue to drop
off in the afternoon.

Further west, forecast soundings are far less impressive.  While
winds east of Lake Ontario are forecast to be near 65 kts under a
6000` cap, the low level jet is about 10-15kts lower underneath
4000` cap east of Lake Erie early, with both fields dropping
throughout the day.  The result east of Lake Erie should be notably
less overall snowfall.  Blowing snow may be an issue where snow
accumulates in upslope regions south of the Buffalo Metro area. The
Monday morning commute may be more hindered by power outages and
road closures than reduced visibilities, mainly during Monday
morning.

Later Monday night through Tuesday night, lake effect snow SE of
Lake Ontario will GRADUALLY end as flurries as surface high pressure
will approach the region.  Temperatures will still be about 15F
below normal, generally in the lower 20s, but at least winds will be
no longer an issue. Otherwise expect variable clouds from a thinning
upslope low level cloud deck.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
While there will not be much weather to deal with for the bulk of
this period...we will likely experience the effects of another
`cutter` storm for the weekend. Otherwise...we can anticipate a
general day to day warming trend with the mercury ending up above
normal by the time we deal with another possible wind event. Its a
little unusual that there is less run to run and model to model
consistency for the start of this period than the ending...so that
being said...confidence will generally increase with the forecast as
we head into the weekend. The day to day details...

High pressure will extend east to our area from the northern plains
on Wednesday. While this is the most consistent solution...there are
packages that depict a weak inverted trough splitting the feature.
This would result in a little snow across our region later Wednesday
and Wednesday night...but given the inconsistency with this solution
and the fact that it is somewhat of an outlier...will back off on
pops and only use slight chc 20s. Again...this is a low confidence
solution for Wednesday afternoon and night...so be sure to check
back for a more concrete forecast.

For Thursday...there is much better agreement that a surface based
ridge over the Upper Mississippi Valley will build east across the
Lower Great lakes. This will promote fair dry weather with little
wind and temps that will peak between 25 and 30.

The area of high pressure will push off the coast of New England
Thursday night and Friday. While this should maintain fair weather
over our region...it will gradually set up a return flow of
moisture that will precede the next storm system.

A disturbance in the southern stream of the split flow will move out
of the southern Rockies late Friday with cyclogenesis over the
southern plains and Lower Mississippi Valley Friday night. While
guidance is not suggesting a strong `cutter` storm like the one that
will seriously impact our region in the near term...it does depict a
deepening sub 1000mb system that will pass by to our west. This
should lead to some mixed precipitation along with some gusty winds
late Friday night and Saturday.

&&

.AVIATION /01Z SUNDAY THROUGH THURSDAY/...
As of early evening a swath of stratus and attendant MVFR to lower-
end VFR ceilings (with some IFR across the Southern Tier) continues
to push its way northeastward across the area...with the leading edge
of this now lying across the eastern Finger Lakes. This will continue
to spread northeastward across the rest of the area through mid to
late evening...with the lowest ceilings found across the higher
terrain. Otherwise a few spotty light showers will also work across
the area through this evening...though these will have little if any
impact on flight conditions.

As we progress deeper into the night...more widespread showers will
move into the area late tonight and early Sunday. Expect CIGS/VSBY
to deteriorate to MVFR overnight, with some IFR possible across higher
terrain. Low level wind shear will develop late tonight and Sunday
morning as a strong low level jet crosses the region.

A few more rain showers will occur along the cold front during the
day Sunday. Strong winds will develop just behind the cold frontal
passage, with peak gusts of up to 65 knots likely Sunday afternoon
and evening northeast of Lakes Erie and Ontario including KBUF,
KIAG, KROC, and KART. CIGS will run mainly MVFR behind the cold
front.

Outlook...

Sunday night...Continued strong winds, otherwise MVFR/IFR
with lake effect snow and blowing snow east of the lakes.
Monday...VFR/MVFR in scattered snow showers. Local IFR in heavier
lake effect snow and blowing snow east of Lake Ontario.
Tuesday...VFR with local IFR in scattered lake effect snow showers.
Wednesday...A chance of IFR in snow.
Thursday...VFR, with local IFR in scattered lake effect snow showers.

&&

.MARINE...
A powerful storm system will track through the Central Great Lakes
and into western Quebec late tonight through Sunday night. Model
consensus continues to show 925mb winds of 60-70 knots in a post-
frontal cold air advection regime. This will produce powerful
winds on Lakes Erie and Ontario, with peak sustained winds at 50
knot storms with gusts of 65 knots likely at times. This will
generate significant wave heights of 25 feet on Lake Ontario, with
an occasional wave over 30 feet. Storm Warning are in effect for
both Lakes Erie and Ontario.

&&

.HYDROLOGY...
A period of rain will develop tonight into Sunday. Rainfall
amounts look to be relatively minor with about a quarter to
perhaps a third of an inch expected. Temperatures will rise
tonight into Sunday with Thawing Degree Hours reaching a
threshold where ice begins to move by tonight. Ice thickness is
only around 2-3 inches on the Buffalo creeks. Ice of this
thickness typically breaks up rather quickly, resulting in ice
flows and minor jams. Typically, this is not enough ice to cause
major ice jams, but there is some risk that there are larger
chunks along the shores or locked in place. The most susceptible
areas to ice jams are the Buffalo Creeks and Cattaraugus Creek,
although they can happen anywhere.

&&

.TIDES/COASTAL FLOODING...
Powerful winds gusting up to 75 mph will result in significant water
rises in the eastern basins of Lake Erie and Lake Ontario
Sunday and Sunday night.

Lake Erie...Lakeshore flooding is expected, and this is likely
to be a high end event. Guidance suggests the water level at
Buffalo may exceed 11 feet above low water datum. The wildcard
is how much the lake ice will restrict the seiche. During a
modest wind event a few days ago, satellite imagery showed the
ice on Lake Erie moving, suggesting it is not fast ice and the
wind will be able to move the water and ice significantly.

As a result, this may impact some locations which are not
typically impacted. For reference, warning criteria is 8 ft. If
the water level at Buffalo exceeds 10 feet above low water
datum, flooding may occur at Canalside and in the Old First Ward
section of Buffalo.

In addition, rises will break up ice in place on the lake, and
this will get pushed onto shoreline areas likely causing
damage to the immediate lakeshore, including the Buffalo Harbor
and Buffalo waterfront. Ice chunks may damage structures, and
even get pushed into rivers and creeks flowing into Lake Erie. Ice
will also get pushed across the Niagara River Ice Boom into the
Upper Niagara River likely causing damage along shoreline areas
of the Upper Niagara River.

The highest water levels will be Sunday afternoon and early
Sunday evening.

Lake Ontario...Significant water rises and high waves are
expected to impact shoreline areas from Oswego county to the
Saint Lawrence River. Ice in place, especially at the northeast
end extending to the Saint Lawrence River will get pushed onto
shoreline areas likely causing damaging. Areas which may be
particularly vulnerable to flooding and ice damage are Sandy
Pond, Black River Bay, Chaumont Bay, and the Thousand Islands
Region of the Saint Lawrence River. Ice blocks will get pushed
onshore, and possibly into rivers and creeks flowing into Lake
Ontario. While Lake Ontario does not respond as dramatically to
a lake seiche, guidance suggests a 1-2 foot rise across the
eastern end of the Lake. This combined with waves which may
reach 25 feet is likely to have a major impact on the immediate
lakeshore.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...High Wind Warning from 7 AM Sunday to 10 AM EST Monday for
     NYZ001>003-010-011-019-085.
     Lakeshore Flood Warning from 7 AM Sunday to 4 AM EST Monday
     for NYZ001-010-019-085.
     Winter Weather Advisory from 3 PM Sunday to 1 PM EST Monday
     for NYZ012-019-020-085.
     High Wind Warning from 10 AM Sunday to 10 AM EST Monday for
     NYZ004>008-012>014-020-021.
     Lakeshore Flood Warning from 4 PM Sunday to 1 PM EST Monday
     for NYZ006-007.
     Blizzard Warning from 6 PM Sunday to 4 PM EST Monday for
     NYZ006>008.
     Wind Advisory from 1 AM to 7 AM EST Sunday for NYZ019.
     Winter Weather Advisory from 3 PM Sunday to 4 AM EST Monday
     for NYZ010-011.
MARINE...Gale Warning from 10 AM Sunday to 4 AM EST Monday for LEZ020.
         Storm Warning from 10 AM Sunday to 4 AM EST Monday for
         LEZ040-041.
         Gale Warning from 10 AM Sunday to 4 AM EST Monday for
         LOZ030.
         Storm Warning from 10 AM Sunday to 7 AM EST Monday for
         LOZ042>044-062>064.
         Storm Warning from 1 PM Sunday to 7 AM EST Monday for
         LOZ045-065.

&&

$$

SYNOPSIS...Hitchcock/JJR
NEAR TERM...Hitchcock/JJR
SHORT TERM...RSH/Zaff
LONG TERM...RSH
AVIATION...Hitchcock/JJR
MARINE...Hitchcock/JJR
HYDROLOGY...TMA/Apffel
TIDES/COASTAL FLOODING...TMA/Apffel/Hitchcock


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