Area Forecast Discussion
Issued by NWS Buffalo, NY

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000
FXUS61 KBUF 160050
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
750 PM EST Wed Feb 15 2017

.SYNOPSIS...
Lake effect snows will continue tonight southeast of the lakes as
cold air spills across the region behind a low pressure system
rapidly deepening off the New England coast. The lake snows will
persist Thursday morning before tapering off Thursday afternoon and
night as high pressure builds into the region. This high will bring
fair weather and much warmer temperatures for the weekend into early
next week.

&&

.NEAR TERM /THROUGH THURSDAY/...
Upgraded Southern Erie and Wyoming counties to a lake effect snow
warning based on estimated new snowfall of 4-6 inches so far today
in that area and more to come overnight. Upslope flow and the
upstream connection to Lake Huron has become more broad and robust,
extending farther north into Southern Erie and Wyoming counties.

A strong upper-level low can be seen on WV imagery spinning near the
Saint Lawrence valley. The parent low over the Saint Lawrence valley
is giving way to a coastal low which will rapidly deepen just east
of the New England coast tonight. The area of synoptically driven
snow crossing the area is already evolving into lake enhanced and
lake effect snow as colder air rushes into the Lower Great Lakes and
850 hPa temperatures fall to about -14C.

Through mid evening, the most concentrated snow will fall across the
higher terrain of the Chautauqua Ridge and also the higher terrain
of Southern Erie and Wyoming counties due to a combination of
upslope flow and lake enhancement. Snowfall rates of 1 to 1.5 inches
per hour are likely in these areas through mid evening. A Georgian
Bay band is now also evident, cutting through eastern Niagara,
southwest Orleans, and Genesee counties. Snowfall rates may briefly
reach 1 inch per hour in this as well, although it should remain
transient and not focus on any one location for long. Farther east,
not much is going on yet from Rochester to western Oswego County,
but this should fill in by mid evening as moisture and cold air
deepens.

A lake effect snow advisory continues for the southern shoreline of
Lake Ontario. Greatest lake effect snow totals within the advisory
will likely be from Niagara County to around Hilton in Monroe County
(on a Georgian Bay connection), and then from NE Monroe County to
western Oswego County. The northwesterly flow will bring a Lake
Huron connection into the western Southern Tier along with upslope
lake enhancement along the Chautauqua Ridge and Southern Erie,
western Wyoming counties. Lake effect snow equilibrium levels will
be similar off Lake Erie, around 6-8k feet, with deep moisture
through a fairly deep dentritic snow growth zone. With an upstream
connection likely to focus a narrow band of snow across the
Chautauqua Ridge, up to a foot of fresh snow is possible tonight. A
lake effect snow warning continues for Chautauqua, Cattaraugus,
Southern Erie and Wyoming counties. For the Tug Hill region, snow
will be primarily synoptic, upslope enhanced from the wrap around
moisture behind the upper level low. Highest amounts will
concentrate on the NW upslope side of the Tug Hill, and thus a
winter weather advisory is in effect for Jefferson and Lewis
counties, since there will be no real lake enhancement there.

Snow will taper off across the region from midday to afternoon on
Thursday as the upper level low move into the Canadian maritimes,
and high pressure builds in from the west.

Temperatures will fall into this evening with cold air advection
across the region. Temperatures will bottom out in the low 20s and
teens tonight, with wind chill values in the single digits
overnight. Temperatures will recover very little on Thursday, with
highs topping out in the mid 20s.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/...
Moving into the weekend...Western and North-Central New York will
enter a quiet period, as a deep upper level trough departs the
region and is replaced by upper level ridging. Any lingering lake
effect showers will end from west to east Thursday night as mid-
level ridging encroaches on the area and 850mb temps rise above
critical thresholds. Dry conditions will then persist through the
weekend as broad upper-level ridging expands across the region. Lake-
induced cloud cover Thursday night into Friday morning should give
way to passing high clouds Friday into Saturday as a warm front
crosses the region and then a passing shortwave skirts by to our
north Saturday night. While the GFS/NAM try to generate some light
shower activity along the warm front Saturday, this seems highly
improbable, given rising heights and a lack of moisture but have
left a slight chance east of Lake Ontario Saturday night closer to
the shortwave.

Regarding temperatures, the aforementioned upper level ridging will
introduce a significant warmup to the region this weekend. While
highs on Friday will run near seasonal normals, in the upper 20s to
lower 30s, it will feel positively spring-like Saturday into Sunday
as heights rise substantially and surface temperatures climb into
the mid to upper 40s in Western NY, with cooler readings in the
upper 30s across the North Country. Lows in the 20s Friday night
will give way to low to mid 30s Saturday night.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
Above normal temperatures continue to be expected Sunday into next
week as Pacific-sourced air shifts across the northern tier of the
CONUS sealing off any significant arctic air intrusions. While there
is high confidence for temperatures running above seasonal
averages...there is lower confidence in exactly how warm we will get
due to variance in model forecasts. The spread in the 12z GEFS
plumes for 2-meter temperatures at KBUF becomes quite large from
Monday night into next week. Another example of this model variance
is with how the GFS and EC are handling a mid level disturbance
passing over southern Quebec and Maine Sunday into Monday. The GFS
shows this disturbance only bringing a quick moving shortwave while
the EC shows the shortwave will dig out a deeper closed low passing
over New England which would send a colder shot of air south across
New England toward New York.

This variance in recent guidance has lead to using a blend of
guidance for temperatures during this period which still averages
out to a several day stretch where temperatures will feel more like
late March/Early April than mid-February. Forecast highs are in the
mid 40s to low 50s Sun-Wed for western NY with highs in the upper
30s to low 40s for the North Country. Overnight lows will range from
the low to mid 30s for western NY and mid/upper 20s to low 30s for
the North Country.

A moisture starved front on Sunday will likely pass by dry but have
left slight change POPS east of Lake Ontario closer to the upper
shortwave. Otherwise conditions will remain dry through Monday.
Low/slight chance POPs return back into the forecast for Monday
night-Wednesday as models show another front crossing our region
sometime during the first half of next week. The GFS is faster and
stronger with the fropa while the EC is slower and actually shows
the front washing out across western NY on Wednesday.

&&

.AVIATION /01Z THURSDAY THROUGH MONDAY/...
Widespread lake effect and lake enhanced snow will continue
southeast of the lakes tonight with IFR conditions. The worst
conditions are expected to focus along the Chautauqua Ridge with
lake enhancement and upslope flow, with the steadier snow also
reaching KJHW. Another area of steadier snow showers will focus
along the south shore of Lake Ontario. This will bring IFR
conditions at times to KROC from mid evening through Thursday
morning, although the most persistent snow will likely focus both
east and west of Rochester. East of Lake Ontario wrap around snow
from a rapidly strengthening coastal low will bring periods of snow
with IFR, including KART. KBUF and KIAG stand to be least impacted
by this, with most of the snow remaining just south, east, and north
of those airfields.

The snow southeast of the lakes will gradually diminish from late
morning through mid afternoon Thursday, with IFR becoming more
spotty and improving to MVFR. The snow will end in most locations by
late in the day with VSBY returning to VFR, although low
stratocumulus will likely continue MVFR CIGS.

Outlook...

Friday...A chance of snow showers/MVFR southeast of Lake Ontario...
otherwise mainly VFR.
Saturday through Monday...VFR.

&&

.MARINE...
Moderate to strong northwesterlies will continue tonight and
Thursday on the Lower Great Lakes. Winds will be strongest on Lake
Ontario overnight in conjunction with a rapidly deepening surface
low off the New England coastline. Winds here will likely peak
around 30 knots, while farther to the west winds will not be as
strong.

Winds and waves will diminish Thursday night and into Friday as a
surface ridge axis nears the lakes from the west.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Winter Weather Advisory until 4 PM EST Thursday for NYZ007-008.
     Lake Effect Snow Advisory until 7 PM EST Thursday for
     NYZ001>006.
     Lake Effect Snow Warning until 4 PM EST Thursday for NYZ012-
     019-020-085.
MARINE...Small Craft Advisory until 7 PM EST Thursday for LEZ040-041.
         Small Craft Advisory until 7 AM EST Friday for
         LOZ042>045.

&&

$$

SYNOPSIS...CHURCH/HITCHCOCK
NEAR TERM...CHURCH/HITCHCOCK
SHORT TERM...WOOD
LONG TERM...SMITH
AVIATION...HITCHCOCK
MARINE...CHURCH/HITCHCOCK



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