WX in text

611
FXUS61 KBUF 111142
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
642 AM EST Wed Dec 11 2024

.SYNOPSIS...
Rain will increase across the region today. The rain will change
over to wet snow from west to east with some minor accumulations
across the higher terrain possible by this evening. Locally heavy
lake effect snow will then develop east of Lake Erie and Lake
Ontario tonight and continue through early Friday, before another
warming trend arrives over the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
Low pressure wave over central Lake Ontario early this morning
with another wave moving through the Southern Tier of New York
with a cold front extending southward. Within the warm sector
ahead of the two surface waves, increasing area of rain working
northward across central and eastern New York. Plentiful low-
level moisture within the cold sector across western New York
with some very light rain, drizzle and areas of fog, some of
which is locally dense across the western Southern Tier and
along the Lake Erie shoreline.

Main mid level trough axis across the Mississippi Valley will move
across the Great Lakes today, eventually taking on a negative
tilt. This will result in a tightening of a baroclinic zone on
the eastern flank of the trough. A frontal wave will northward
from the Carolinas into eastern Pennsylvania by this afternoon
allowing the coverage of rain to expand back westward across the
region through the day today. Strengthening cold advection on
the western flank of this frontal zone will begin the process of
changing rain over to wet snow, first across the higher terrain
east of Lake Erie and Lake Ontario and then everywhere before
lake effect snows fire up east of both lakes. Where precipitation
changes over to snow first some slushy accumulations (1-2
inches) will be possible by this evening. Winds will also pick
up by late in the day and early tonight, with gusts up to 45 mph
possible, with the strongest winds downwind of the lakes. It
will also turn much colder with temperatures falling off during
the course of the day. Expect temperatures to fall into the 30s
to upper 20s in spots by evening.

Colder air will continue to deepen across the region tonight
starting a significant lake effect snow event east of both
lakes. Lake induced equilibrium levels will increase to around
15K feet late tonight as the core of the coldest mid level air
starts to make it way into region.

Off Lake Erie...

The expectation is that a single band of lake effect snow will
quickly develop toward this evening as the synoptic precipitation
makes its way out of the region. The initial lake band will
develop well south of Buffalo across the western Southern Tier
and southern Erie county. The band will begin to strengthen in
this area, then start to move northward through Erie county
overnight. Backing steering flow ahead of an approaching
shortwave will lift the band as far north as the city of Buffalo
and the Buffalo Airport over to Batavia between midnight
tonight and daybreak Thursday morning. Snowfall rates likely
increasing to 2 to 3 inches per hour within the heart of the
band. Snowfall amounts through tonight likely reaching a foot or
more centered on southern Erie county. Strong winds will result
in blowing and drifting snow along with near whiteout conditions
at times within and along the fringes of the lake band.

Off Lake Ontario...

The lake effect snow will develop later this evening as the synoptic
precipitation exits. Initial lake enhanced upslope regime across the
Tug Hill Plateau will evolve into a more pure lake effect band later
tonight, with the band of lake snow setting up from near
Watertown/Fort Drum to Lowville. The band will likely remain
disorganized to some degree as some low level shear will be present.
This will limit accumulations tonight to just a few inches.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
...HEAVY LAKE EFFECT SNOW THROUGH FRIDAY...

The pattern will briefly amplify across North America, with a strong
ridge building over the Rockies and a strong, deep trough digging
into the east. This trough will deliver a very cold airmass to the
region, supporting strong instability over the lakes and another
heavy lake effect snow event. Lake induced equilibrium levels will
peak at around 15K feet through early Thursday as the coldest mid
level air crosses the region, then steadily lower later Thursday
through Friday as the cold airmass becomes more shallow with time.

Off Lake Erie...

A well developed lake band will stretch from the Dunkirk/Fredonia
area to the Buffalo Southtowns, and into northern Wyoming and
southern Genesee counties around daybreak Thursday morning. Guidance
continues to suggest that backing low level flow ahead of a
shortwave moving through the base of the mid level trough will carry
the northern edge of the band all the way north to near or over
Buffalo and Batavia briefly early Thursday morning before settling
back south a little towards central Erie County and the
Wyoming/Genesee County border by mid morning Thursday.

Latest guidance suggests the band may creep back north towards the
immediate Buffalo Southtowns and possibly South Buffalo and some of
the eastern suburbs for a time later Thursday through Thursday
evening, before moving back south again Thursday night. The band
will generally remain across Southern Erie County and the western
Southern Tier from later Thursday night through Friday, where it
will steadily weaken as inversion heights lower.

The Lake Erie band should reach peak intensity for much of Thursday,
when snowfall rates may reach 2-3" per hour. Expect a weakening
trend Thursday night and especially Friday.

As far as storm totals go, expect 2-3 feet in the most persistent
bands. The bullseye is most likely to be in southern Erie County,
with 1-2 feet over western Chautauqua, far northwest Cattaraugus,
and western Wyoming counties. The more immediate Buffalo Southtowns
(that are located in the northern Erie zone) and southern Genesee
County may see 10-20 inches if the band persists long enough that far
north. This is another extremely close call for the City of Buffalo,
with South Buffalo possibly accumulating 1 foot or more while North
Buffalo has very little.

Conditions seem supportive of strong inland penetration with this
band, with moderate accumulations possibly extending into the
western Finger Lakes. Also included an Advisory for Livingston
County, with 4-7" possible in a narrow band across central or
northern Livingston County. This could potentially extend into
portions of Ontario County as well, but confidence is lower that far
from the lake. Snow showers will occasionally peel off the eastern
end of the band and make it all the way into Oswego County and the
southern Tug Hill.

Off Lake Ontario...

A band of lake snow will move north towards Watertown and Fort Drum
by Thursday morning. The band may not be particularly strong at
first, with some shear still located in the boundary layer. The band
should strengthen Thursday morning as boundary layer flow becomes
better aligned. The band should spend most of Thursday over or near
Watertown and central Jefferson County.

Boundary layer flow will then veer more westerly Thursday evening,
carrying the band a little south to center more on the northern and
central Tug Hill region. The highest snowfall rates are likely to
occur Thursday night, when the most favorable convergence is
forecast over the lake, and when lake effect snow will begin to
intersect terrain. Friday, lake effect snow should remain near the
Oswego/Jefferson County border and extending inland across the Tug
Hill Plateau. Inversion heights will steadily lower and the airmass
will dry out, resulting in a weakening of the band later in the day,
and will also force it to shrink back towards the lakeshore.

The Lake Ontario band will likely reach peak intensity later
Thursday through Thursday night or early Friday, when snowfall rates
may reach 2-3" per hour. Expect a weakening trend later Friday as
inversion heights lower.

As far a storm totals go, expect 2-3 feet in the most persistent
bands. The bullseye will most likely be found across the northern
Tug Hill to just south and east of Watertown. This will be
surrounded by a larger footprint of 1-2 feet of snow including
Watertown and central Jefferson County, central and northern Lewis
County, and far northern Oswego County.

Finally, it will turn very windy through Thursday evening. Winds may
gust up to 40 mph at times, resulting in considerable blowing and
drifting snow where lake effect snow occurs.

Outside of lake effect areas, expect mainly dry weather and even
some sunshine Thursday through Friday. It will be quite cold, with
highs in the mid 20s for lower elevations and around 20 for higher
terrain Thursday and Friday. Lows Thursday night will be in the
teens, with wind chills in the single digits.

Guidance is split on the potential for lingering lake snow east of
Lake Ontario through Friday night. The potential for lake snow in
this scenario is based on light westerly wind potential, where a
convergence band may linger over the eastern third of the lake,
extending into Oswego and Jefferson county some. Guidance that does
not continue the light lake response has slightly strong southerly
winds that wash out any lake response. This will need to be watched
as we get closer to the end of the week. Current guidance that
favors the continued lake snow, results in generally light snowfall
amounts of 1 to 3 inches, and mainly closer to the lake shore.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
Surface high pressure over NY/PA and New England Saturday morning
will move east and off the New England coast later in the day. This
will provide mainly dry weather, and after a chilly start, a notable
warming trend will develop. Highs will reach the upper 30s to near
40 in Western NY, and upper 20s to lower 30s for the North Country.

The warming trend will continue into Sunday, with highs well into
the 40s for most lower elevation areas. A weakening mid level
shortwave will cross the eastern Great Lakes later Saturday night
through Sunday night. This system will produce some light rain
across the region, which may mix with wet snow at the start and
across higher terrain.

Another trough and surface cold front will approach Tuesday, with
increasing chances of showers. Temperatures will continue to run
above average early next week, with much of the precipitation
falling as just rain.

&&

.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
Abundant low-level moisture will keep patchy light rain, drizzle and
areas of fog across far western New York this morning, including
KJHW, KBUF, KIAG, and KROC. This will produce a mix of IFR to
LIFR conditions.

An area of rain spreading into central and eastern New York
this morning will expand westward through the day. Colder air
moving in from the west will change the rain to wet snow over
higher terrain by midday or early afternoon, with wet snow
likely elsewhere by early this evening. Conditions will remain
MVFR/IFR with VLIFR possible across higher terrain including
KJHW.

Outlook...

Tonight...MVFR/IFR with wet snow tapering off, then heavier lake
effect snow east of the lakes with local LIFR.
Thursday through Friday...Local lake effect snow with LIFR east of
Lake Erie and Lake Ontario. Close call for KBUF, heavier snow may
remain just south of the airfield. VFR/MVFR elsewhere.
Saturday...Mainly VFR with a chance of rain or snow showers.
Sunday...MVFR to IFR with rain showers.

&&

.MARINE...
Quiet marine conditions expected through most of today as a weak
pressure gradient across the lower Great Lakes maintains
relatively light winds.

Westerly winds will sharply increase late today and this evening
behind the passage of a strong cold front. Sustained speeds of
25 to 30 knots are likely from tonight through Thursday
afternoon with a period of gale force winds, especially behind
the cold front tonight into the first half of Thursday over the
eastern basin of Lake Erie and all of Lake Ontario. Gale Warning
have been issued on both lakes during this time frame.

Conditions will improve on Lake Erie and Lake Ontario Friday as
high pressure nears the region and winds lighten considerably
and turn more southerly.

&&

.HYDROLOGY...
Another round of rain is expected through today. Overall,
rainfall amounts will be on the order of a tenth to a quarter
inch from the Genesee Valley west across the Niagara Frontier
and the Southern Tier. East of the Genesee Valley, amounts will
range from a third to three quarters of an inch. These rainfall
amounts, combined with ongoing snowmelt, will bring within-bank
rises on area rivers and creeks through midweek. Official
forecasts from the RFC along with ensemble forecasts continue to
suggest a low chance of flooding. The Black River basin, with
more snow to melt and higher rainfall amounts, will see the most
significant rises later this week, and a low chance of reaching
minor flood stage.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Lake Effect Snow Warning from 7 PM this evening to 7 PM EST
     Friday for NYZ006>008.
     Lake Effect Snow Warning from 10 PM this evening to 1 PM EST
     Friday for NYZ010-011.
     Lake Effect Snow Warning from 4 PM this afternoon to 1 PM EST
     Friday for NYZ012-019-020-085.
     Winter Weather Advisory from 7 PM this evening to 4 AM EST
     Friday for NYZ013.
MARINE...Small Craft Advisory from 6 PM this evening to 10 PM EST
         Thursday for LEZ020.
         Gale Warning from 7 PM this evening to 4 PM EST Thursday
         for LEZ040-041.
         Small Craft Advisory from 6 PM this evening to 10 PM
         EST Thursday for LOZ030.
         Gale Warning from 10 PM this evening to 4 PM EST Thursday
         for LOZ042>045-062>065.

&&

$$

SYNOPSIS...AR/TMA
NEAR TERM...TMA
SHORT TERM...Hitchcock/SW
LONG TERM...Hitchcock
AVIATION...AR/TMA
MARINE...AR/TMA
HYDROLOGY...AR/Hitchcock/TMA

NWS BUF Office Area Forecast Discussion