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000
FXUS61 KBUF 201452
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
952 AM EST Tue Nov 20 2018

.SYNOPSIS...
A weak clipper will produce some light snow across the region today
with minor accumulations mainly across the higher terrain east of
the lakes. A stronger clipper will move through the region late
tonight and Wednesday, producing more widespread snow showers and a
period of briefly heavy lake effect snow east and northeast of the
lakes. A few lake effect snow showers will continue southeast of the
lakes Wednesday night. Near record cold is expected for Thanksgiving
Day before a warming trend arrives by the weekend.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
As of 950 am...the axis of a mid level shortwave and its associated
weak surface cold front has pushed into far western New York...with
light snow shower activity becoming increasingly widespread across
the region from west to east. This system will push eastward across
the rest of the region through early to mid afternoon...with the
attendant light snow showers lasting through about midday across
western New York...and through about mid afternoon east of Lake
Ontario. The best coverage will be east of the lakes where some very
modest lake enhancement will occur and may allow for 1-2 inches of
accumulation across the higher terrain east of Lakes Erie and
Ontario today, with less than an inch falling elsewhere. The majority
of the snow will taper off and end from west to east this afternoon.
Some very limited lake effect snow may continue into this evening near
the southeast corner of Lake Ontario, but any accumulations with this
will be very light with diminishing moisture and lowering inversion
heights.

Highs today will reach the lower to mid 30s in most areas by late
morning or midday...before temperatures pull back a few degrees during
the afternoon as cold advection begins.

A weak surface ridge will briefly cross the eastern Great Lakes this
evening, with most areas dry. The one exception may be southeast of
Lake Ontario, where some limited/light lake effect snow may continue
from eastern Wayne to Oswego counties.

Late tonight and Wednesday our attention turns to a much stronger
clipper that will pass by just north of the lakes. Stronger large
scale ascent and much stronger low level convergence just ahead of
an arctic front will produce a more robust lake response, with lake
induced equilibrium levels rising to 8-10K feet just ahead of the
arctic boundary. From a synoptic standpoint, the clipper will
produce a few snow showers with a coating to an inch of accumulation
outside of lake effect areas.

Winds and Temperatures...

It will become quite windy on Wednesday with a sharp pressure
gradient, cold advection, and steepening lapse rates promoting
downward momentum transfer. Expect gusts of 30-35 knots in the
typically windier lake plain locations, and 25-30 knots farther
inland. This will produce blowing and drifting snow in areas which
receive accumulating snow.

Highs will be in the low to mid 30s briefly Wednesday morning.
Strong cold advection will then force temperatures to drop through
the 20s in the afternoon, with wind chills dropping into the teens.

Now for the lake effect...

Off Lake Erie...

Expect a band of snow to develop rapidly after 06Z over the lake and
extend northeast into the Buffalo Metro area. This band may briefly
brush southern Niagara and Orleans counties as well before settling
south across the Buffalo Metro area and Genesee County, intensifying
as it moves south. The snow will not last in any one location for
more than a few hours, but may produce 1-2 inch per hour rates for a
brief time. The northeast end of the band may briefly reach Monroe
County as well with minor accumulations in the western suburbs of
Rochester. The band should be just south of Buffalo and Batavia by
12Z Wed, then push bodily onshore and focus heavy snow on the
Chautauqua Ridge for a few hours early Wednesday morning as it
becomes captured by the arctic front. After late morning, expect
transient bands of snow to focus on the western Southern Tier, with
any upstream connection to Lake Huron ending up in NW PA or NE OH by
late in the day.

The fast band motion will limit accumulation potential somewhat, but
if the band becomes strong enough it may drop a quick 2-4 or 3-5
inches from the Buffalo Metro area and western Genesee County
southward across the higher terrain. In addition, rapidly increasing
winds will produce plenty of blowing and drifting snow and poor
visibility.

Off Lake Ontario...

Expect a similar evolution a few hours later. A weak band of lake
effect snow may drift north across the Tug Hill region through the
middle of the night. This will then intensify across central
Jefferson County including Watertown by early Wednesday morning.
This band of snow will then move fairly quickly south across the Tug
Hill region through the late morning hours and cross Oswego County
early afternoon. Snowfall rates may briefly reach 1-2 inches per
hour in this band. During the mid to late afternoon a somewhat
weaker band of lake effect snow will move onshore from
Orleans/Monroe counties to portions of Wayne and Cayuga counties as
boundary layer flow veers quickly to the northwest. Mesoscale model
guidance suggests it may develop an upstream connection to Georgian
Bay during this time frame, although the steadily veering boundary
layer flow should keep the band moving enough to keep accumulations
somewhat in check along the south shore of Lake Ontario.

The fast band motion will limit accumulation potential somewhat, but
if the band becomes strong enough it may drop a quick 2-4 or 3-5
inches from central Jefferson County including Watertown, southward
across the Tug Hill region. Expect 1-2 inches later in the afternoon
from western Oswego County westward along the south shore of the
lake to Orleans County, including the Rochester area. There will be
some additional accumulations in this area Wednesday night. In
addition, rapidly increasing winds will produce plenty of blowing
and drifting snow and poor visibility.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
Wednesday night through Thursday night will likely bring the coldest
temperatures of the season. Wednesday night temperatures will bottom
out around the low to mid teens for areas near the lakes, and in the
single digits to near zero across the higher terrain. Temperatures
on Wednesday night and Thursday will likely be the coldest
temperatures that most areas experience since this past March or
February. As the area of Arctic high pressure moves into the
northern Great Lakes, behind a departing upper level trough, cold
air advection that began on Wednesday will continue through
Wednesday night. The Arctic high will be centered over WNY by
Thursday evening.

850Ts on Wednesday night will bottom out around -20C from WNY to
near -22C over N.C.NY. If these 850Ts come to fruition, it will be
in the top five coldest 850Ts recorded in the month of November for
the Buffalo sounding location. The coldest 850 temperature per NWS
archive was -21C on November 21, 1987, with that number in jeopardy
of getting eclipsed on Thursday morning. Light lake effect snow will
continue from earlier on Wednesday through early Thursday morning.
Lake effect snow that does persist through the night should taper
off through the early morning on Thursday. Moisture levels will drop
overnight Wednesday as the Arctic high approaches the area on
Thursday, with the GFS and NAM showing PWATs of around a tenth of an
inch. The Euro though does show some slightly better moisture
content. With 850Ts this cold, any moisture that will be present
will likely be in the snow growth zone. Likely POPs will continue
very early on this period as the lake effect snow starts to wind
down. With the above in mind, will trend POPs down to chance for
lake effect southeast of the lakes through the early morning before
sunrise. As ridging increases with the approaching high, resulting
in increasing subsidence POPs will continue to lower after sunrise.
Any continued lake effect snow showers will continue to decrease in
coverage through the mid morning on Thursday. Snow accumulations
from the lake effect snow should remain below an inch overnight
Wednesday night, with most of that falling early in the period.

High temperatures on Thursday will be in the teens east of Lake
Ontario, and in the upper teens to low 20s across the rest of the
area. High temperatures on Thursday will be around 25 degrees below
normal. Rochester and Buffalo could experience their top 5 coldest
Thanksgivings on record.

Thursday night into Friday will start out with continued cold
temperatures from the Arctic high over the area, but some warmer
temperatures will build into the area as the high shifts to the east
and a southerly flow establishes starting Friday morning. Lows on
Thursday night and Friday morning will be chilly once again with
temperatures in the single digits to near zero in the higher terrain
and in the low to mid teens closer to the lakes. Those who plan to
venture out shopping Thursday night and Friday morning should dress
appropriately for the cold conditions.

Friday high temperatures will be in the mid to upper 30s near the
lakes, and in the upper 20s to low 30s across the higher terrain.
The area should experience mostly cloud free conditions for most of
the day, with some clouds increasing in the late afternoon and
evening ahead of the next chance for precip starting overnight
Friday night.

&&

.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
The weekend continues to look unsettled with precipitation chances
increasing, but with milder temperatures. Upper level trough will
move slowly across the Great Lakes into the Northeast Conus,
eventually becoming negatively titled over the area. Surface low
over the Carolinas will eventually push toward New York and New
England. Expecting mainly rain for precipitation type, but cannot
rule out pockets of mixed precipitation during the cooler overnight
and early morning periods. Highs should be mainly in the 40s over
the weekend, with overnight lows in the 30s.

A large area of low pressure will approach the area from the Ohio
Valley on Monday, with increasing chances for rain through the day.
Temperatures for Monday will once be in the low to mid 40s across
the area.

&&

.AVIATION /15Z TUESDAY THROUGH SATURDAY/...
A mid level trough and surface cold front will move across the area
this morning and produce areas of snow showers. The best coverage of
the snow showers will be east and northeast of the lakes as some
modest lake enhancement develops. This will produce several hours of
IFR VSBY and MVFR CIGS at most of the TAF sites, with some IFR CIGS
across the higher terrain. Conditions will improve from west to east
this afternoon as the system exits the area, with VSBY returning to
VFR and CIGS a mix of MVFR and VFR. Some very limited lake effect
snow may continue into this evening near the southeast corner of
Lake Ontario with local IFR.

Another, stronger mid level trough and cold front will approach the
area late tonight. This will bring an increasing chance of snow
showers after 06Z Wed, with lake effect snow also developing
initially northeast of the lakes. This heavier lake effect snow may
impact KBUF for a few hours late tonight with conditions near or
below airfield minimums possible. Heavier lake effect snow will
develop near KART shortly before 12Z Wed.

Outlook...

Wednesday...areas of MVFR/IFR in periods of snow showers and lake
effect snow.
Thursday and Friday...VFR.
Saturday...MVFR or IFR as a system moves into or south of the
region with rain.

&&

.MARINE...
A cold front will finish crossing the Lower Great Lakes today,
with west-northwesterly winds increasing from west to east behind
the front through this afternoon. This will produce Small Craft
Advisory-worthy conditions that will last through tonight.

A stronger cold front will then cross the eastern Great Lakes
Wednesday. Latest guidance is a bit stronger, and may result in a
period of Gales on Lake Ontario with high end Small Craft Advisory
conditions on Lake Erie. A Gale Watch remains in effect for Lake
Ontario. The wind will last through Wednesday night before high
pressure builds into the eastern Great Lakes Thursday with
diminishing winds.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Winter Weather Advisory from 4 AM to 4 PM EST Wednesday for
     NYZ007-008-019-020.
     Winter Weather Advisory from 7 AM to 7 PM EST Wednesday for
     NYZ006.
     Winter Weather Advisory from 1 AM to 10 AM EST Wednesday for
     NYZ010-011.
     Winter Weather Advisory from 4 AM to 1 PM EST Wednesday for
     NYZ012-085.
MARINE...Small Craft Advisory from 3 PM this afternoon to 1 AM EST
         Thursday for LEZ040-041.
         Small Craft Advisory from 2 AM to 7 PM EST Wednesday for
         LEZ020.
         Gale Watch from Wednesday morning through Wednesday
         evening for LOZ043>045-063>065.
         Gale Watch from Wednesday morning through Wednesday
         evening for LOZ042-062.
         Small Craft Advisory from 1 PM this afternoon to 10 AM EST
         Wednesday for LOZ043-044.
         Small Craft Advisory until 7 AM EST Wednesday for LOZ042.
         Small Craft Advisory from 6 PM this evening to 10 AM EST
         Wednesday for LOZ045.

&&

$$

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