Area Forecast Discussion
Issued by NWS Buffalo, NY

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS61 KBUF 180111
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
811 PM EST Sun Dec 17 2017

.SYNOPSIS...
High pressure will move east of the region tonight. Temperatures
will warm above freezing Monday as a warm front lifts across the
region, bringing a chance for rain and snow showers into Tuesday.
A cold front will sweeps across the lower Great Lakes Tuesday night,
bringing a return to more wintry conditions by Wednesday.

&&

.NEAR TERM /THROUGH MONDAY/...
Surface high pressure will move off to our east tonight, while the
warm frontal boundary across the Ohio Valley continues to slowly
advance northeast into the forecast area. A weak mid level wave will
approach the forecast area from the upper Great Lakes late tonight
and interact with this boundary. Initially lift will be weak enough
to support some flurries. There will eventually be enough lift late
tonight/early Monday morning to bring some light snow late tonight
across the northern half of the forecast area, particularly across
the North Country. The combination of cloud cover and weak warm air
advection will bring a non-diurnal temperature trend overnight, with
readings climbing into the lower to mid 30s across western New York,
and into the lower to mid 20s in the North Country.

The warm front will get hung up across the forecast area on Monday.
This will bring the best chances for accumulating snowfall across
the North Country, where temperatures will remain cool enough for
all snowfall. 2 to 3 inches of light steady snowfall is possible
there, particularly over the higher terrain of the Tug Hill.
Meanwhile, much of the forecast area south of Lake Ontario will see
very little precipitation until the afternoon when a weak shortwave
riding along the boundary pushes it back southward. This The added
ascent along the boundary, plus the shortwave and low-level moisture
/upslope east of the lakes will help generate some
rain showers across the lake plains, while there may still be enough
cold air over the higher terrain of the western Southern Tier to
support some light snow accumulations on the hill tops. Highs will
be near 40 degrees across western New York to the mid 30s across the
North Country.

&&

.SHORT TERM /MONDAY NIGHT THROUGH THURSDAY NIGHT/...
Monday night a warm frontal boundary draped from Lake Ontario to
the North Country at the start of the night will continue to slowly
push northeastward and out of our area...though our region will
still remain under the influence of broad warm air advection out
ahead of a modest mid level trough/attendant surface low pushing
into the Upper Great Lakes. This will keep plenty of cloud cover in
place along with a continued potential for some light precip...
though with available forcing looking to be rather weak and diffuse
this should be rather spotty...with the best precip chances confined
to the North Country which will lie closest to the departing warm
front. As has been the case for the past two days...simple pattern
recognition...statistical guidance....and model thermal profiles all
suggest that the bulk of whatever precip there is will be in the
form of plain rain...thanks to relatively mild temps in both the
boundary layer and in the main cloud bearing layer...which will
remain too warm to support the formation of ice crystals. About the
only real chance for snow will lie across the North Country...where
temps may be initially cold enough to support more of a rain/snow mix
before slow but steady warm advection forces a changeover to all rain
overnight. Given the steady warm air advection regime...low temps will
occur fairly early in the evening and will range from the lower to mid
30s east of Lake Ontario to the mid and upper 30s elsewhere...before
yielding to steady or slowly rising temperatures overnight.

On Tuesday the aforementioned mid level trough/surface low will make
their way further eastward...and will eventually push their attendant
cold front across our area during the afternoon hours. With only limited
to modest forcing available...expect any precip out ahead of and along
the front to remain largely scattered. The antecedent mild airmass in
place out ahead of the front will result in milder temperatures and a
ptype of all rain...with highs reaching into the lower to mid 40s
areawide...and much of the Genesee Valley/Finger Lakes region even
making a run into the upper 40s. Otherwise the tightening pressure
gradient out ahead of the front will result in an increasingly breezy
to windy day...with the short term guidance packages having trended
stronger with the low level wind field compared to yesterday. As of
this point it now appears that most areas should see wind gusts to
30-35 mph...with the strongest overall winds found downwind of Lake
Erie...where the combination of funnelling effects and a stronger flow
aloft should result in gusts to the 40-45 mph range. The 12Z NAM (which
has a notably stronger low-level wind field and brings the stronger
winds closest to the surface) would even suggest the potential for
some lower-end advisory-range gusts within this latter area...though
with a general warm air advection regime in place and other guidance
remaining notably weaker with the low-level wind field...confidence
in this is not yet high enough for inclusion in the HWO. Nonetheless...
this possibility will be something for us to keep a close eye on over
the next day or so.

Following the frontal passage...a westerly to west-northwesterly flow
of colder air will overspread our region Tuesday night and Wednesday.
Given current lake surface temperatures of around +4C...this airmass
will eventually become cold enough to support a lake response by late
Tuesday evening off Lake Erie...and during the second half of Tuesday
night off Lake Ontario.

Digging a bit further into the forecast details...off Lake Erie the
overall lake response continues to appear rather muted by a general
lack of deep background moisture through midweek...as well as rather
low inversion heights ranging between only 3 and 5 thousand feet. This
should keep any activity fairly scattered and light in nature...with
any lake snows likely to end altogether Wednesday evening as high
pressure and drier air build into the region.

Meanwhile off Lake Ontario...conditions still seem to be at least
somewhat more favorable with somewhat deeper moisture and higher
inversion heights becoming available for a time between later Tuesday
night and early Wednesday...though compared to yesterday this period
of more favorable conditions also appears to be shorter and accompanied
by lower inversion heights than what had been previously projected.
Given this...conditions still appear to be less than ideal for an
overly significant lake response...and thus unworthy of anything higher
than some likely PoPs and modest snowfall accumulations at this vantage
point...with the bulk of these confined to between later Tuesday night
and Wednesday morning. After that time...the lake snows should steadily
wind down Wednesday afternoon and night thanks to the arrival of the
aforementioned ridging and drier air.

Outside of the lake effect areas...the Tuesday night-Wednesday night
time frame should be largely dry...with all areas seeing a return to
colder temperatures for midweek. Speaking more specifically...lows on
Tuesday night will settle back to between the mid 20s and lower 30s
in the wake of the cold front. Highs on Wednesday will then struggle
to get much above the lower to mid 30s...with readings south of Lake
Ontario then largely falling back to the teens and lower 20s Wednesday
night...while the North Country sees readings settle back to around
10 above.

Moving on into the last 24 hours of this period...on Thursday the
surface ridge will slide eastward across our region...and will bring
our region a dry and quiet day...along with high temps ranging from
the lower to mid 20s across the North Country to the lower to mid
30s south of Lake Ontario. The high will then slide eastward into
New England Thursday night...while a strengthening low pressure
system develops into the central Mississippi Valley. Developing
warm air advection out ahead of this system and its advancing warm
front will spread increasing amounts of cloud cover back across our
region...with perhaps a little spotty light wintry precipitation
developing overnight...though a consensus of the medium range
guidance would keep this largely confined to areas from Lake Ontario
and the North Country northward...where the airmass would more
than likely remain cold enough for primarily snow. Otherwise...
low temps will range from the teens east of Lake Ontario to the
20s elsewhere...with readings likely tending to rise in the warm
advection regime overnight.

&&

.LONG TERM /FRIDAY THROUGH SUNDAY/...
A split flow over the country leading into this period will lead to
a fairly tight baroclinic zone that will stretch from the southern
plains to the Upper Great Lakes on Friday. This will be right where
a cutter storm will track into the Great Lakes region. Like previous
runs...mainstream guidance does not have a good handle on the timing
and exact track of the surface low...and in fact...the various
models have traded their positions. The point here...there is low
confidence in the timing of the associated precipitation. There will
be high confidence though that we can anticipate a mixed
precipitation event Thursday night through Friday night.

Any residual mixed precipitation Saturday morning in the wake of the
passing system will end as scattered snow showers during the
afternoon.

High pressure centered over the high plains late Saturday night will
nose to the east across our region for Sunday/Christmas Eve. While
this would promote dry...uneventful weather for the bulk of the
region...there are some ensemble members that suggest that the
surface ridge will stay north of our region. This current outlier
solution would keep the potential for light snow over the region for
Christmas Eve.

Looking ahead to the period between Christmas and New Years...the
long range guidance continues to suggest that the coldest airmass of
the season to this point will dive south into the heart of the
country. Energy ejecting out of a closed storm system over Siberia
is forecast to break down in the coming days with a chunk of its
energy being ejected out across the Kamchatka Peninsula and northern
reaches of the Pacific ocean. Eventually...this very robust bundle
of mid level energy is forecast to help carve out a full latitude
trough over the heart of North America. While highly anomalous
ridging off the West coast would extend from 20N all the way to the
Pole...a large portion 0f the polar vortex would settle south to
northern Ontario. This newly phased pattern would not only include a
cross polar flow...but more importantly would allow H85 temperatures
of <-30c within the vortex to make their way across the northern
plains.

While this long range forecast would place the coldest air of this
outbreak over the plains states...the air would eventually make its
way to the Ohio Valley. Climatologically...this is exactly where it
should be to support significant southwest flow lake effect for our
region. This would also come at a time (between Christmas and New
Years) when impactful southwest flow lake storms seem to be most
common. In a nutshell...the week or so from Christmas to New Years
should feature colder than normal weather with the hint for
substantial lake snows. Stay tuned.

&&

.AVIATION /01Z MONDAY THROUGH FRIDAY/...
A warm front will move north across the region overnight and Monday
bringing spotty snow showers overnight, with more persistent light
snow across the North Country on Monday. Meanwhile precipitation
will change over to rain across western NY on Monday. Currently VFR
cigs across the lake plains and MVFR cigs across the higher terrain
will deteriorate overnight to MVFR in the lake plains and IFR in the
higher terrain as ceilings lower along the frontal boundary.
Eventually most TAF sites (except KROC, which will see some
downslope winds) may go IFR by Monday afternoon as shower coverage
increases with a wave moving along the stalled frontal boundary.

Outlook...

Tuesday...IFR/MVFR with rain likely.
Wednesday...IFR in lake effect snow likely SE of the Lakes, MVFR/VFR
with a chance of snow elsewhere. Thursday...Mainly VFR.
Friday...VFR/MVFR with a chance for rain or snow showers.

&&

.MARINE...
Generally light northeasterly winds will give way to freshening
southwest winds on Lake Erie tonight as a warm front slowly moves
northeast into the lower Great Lakes and a weak clipper approaches
the region. Winds will flirt with small craft advisory criteria for
a brief time tonight as the disturbance passes by, but should remain
just below advisory levels.

Southwesterlies will strengthen further Monday night however, as a
deep area of low pressure centered well to our north crosses Hudson
Bay. THe resulting tightening of the pressure gradient across our
region sending winds into small craft advisory territory across many
zones Monday night into Tuesday, with winds staying brisk as they
veer to the northwest with a passing cold front Tuesday night.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...None.

&&

$$

SYNOPSIS...TMA
NEAR TERM...CHURCH/TMA
SHORT TERM...JJR
LONG TERM...RSH
AVIATION...CHURCH
MARINE...TMA



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.