Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 200829
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
329 AM EST Fri Jan 20 2017

.SYNOPSIS...
A weakening trough will move from southwest to northeast across the
region today and produce a period of rain across Western and Central
NY this afternoon and evening, before weakening to scattered showers
across the North Country tonight. Plenty of low clouds, drizzle, and
patchy fog will persist behind this trough tonight through at least
the first half of the weekend. An area of low pressure is then
forecast to move northward along the east coast early next week.
This system may tap into just enough cold air to allow rain to
change to wet snow later Monday through Tuesday.

&&

.NEAR TERM /THROUGH TONIGHT/...
The drizzle has finally tapered off across most of the region early
this morning as the low level moisture field becomes more shallow
with time. Plenty of low clouds remain however, with areas of fog
mainly across the higher terrain as the stratus deck intersects the
hills. Short term mesoscale model guidance such as the HRRR have a
good handle on the current coverage of low stratus, and suggest it
will scatter out steadily from south to north this morning as
southerly flow increases just off the deck, both advecting out the
moisture and also increasing downslope flow into the lake plains,
further scouring out the low level moisture. This should bring an
end to the fog across higher terrain by mid morning across Western
NY, and midday for the Tug Hill.

Our attention then turns to a sharp mid level trough and weak
surface reflection across the Ohio Valley. This trough will move
steadily northeastward today and enter Western NY this afternoon,
before moving off to the North Country tonight. The trough will de-
amplify with time, allowing the associated DPVA to weaken with time,
and the low level jet also weakens with time. There will still be
enough forcing to support widespread rain as the trough moves into
the western Southern Tier by late morning or midday, but coverage
and intensity of rain will steadily diminish as the trough moves
northeast across the Finger Lakes and Central NY by late afternoon
and evening. By the time the trough reaches the North Country late
this evening and overnight, expect just a few scattered light
showers to be left.

Tonight plenty of low level moisture will be left behind in the wake
of the departing mid level trough. Relatively light and convergent
southwesterly flow will develop across Western NY, and combine with
frictional convergence off Lake Erie and upslope flow to produce
another round of drizzle, low clouds, and fog overnight. This is
likely to last through at least the first half of the weekend, more
on that in the short term section below.

Temperatures will run well above average, with highs in the low to
mid 40s in most locations today. Temperatures will remain in the
lower 40s tonight in most areas, with mid to upper 30s across the
North Country.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
Broad troughing will gradually expand across the western two-thirds
of the country through the coming weekend, forcing upstream riding
downstream across the lower Great Lakes. This will produce a
generally benign forecast across our forecast area through the
period.

While it will certainly be an unseasonably mild weekend across
Western and North-Central New York in the wake of the warm front,
with highs in the 40s, with portions of Western New York even
creeping into the low 50s Saturday...it will be a rather dismal
weekend overall, as low-level moisture currently in place across the
area combined with additional shallow GOMEX moisture being supplied
from the Ohio valley is expected to remain trapped underneath the
ridging overhead. This will keep low clouds trapped across much of
the forecast area, with patchy fog and drizzle likely hanging around
through much of the weekend. The lingering cloud cover will limit
diurnal temperature swings, with lows Saturday night ranging from
the mid 30s in the North Country to the lower 40s in Western New
York. Increasingly northeasterly flow Sunday into Sunday night
will cool things into the 30s across the forecast area.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
While concerns remain over the impending coastal storm expected to
impact the northeastern U.S. Monday into Tuesday...there is far less
certainty with regards to the impact on Western and North-Central
New York at this time. The 12Z GFS run has shifted the deformation
zone on the western periphery of the coastal low sharply to the
east, and now keeps the bulk of the forecast area largely dry, with
the exception the eastern edges of the area. The 12Z ECMWF/GEM
models still attempt to bring a trowal across the heart of the
forecast area late Monday into Monday night, but shunt this feature
northwards into Canada by Tuesday morning. Model profiles do
continue to suggest a changeover to snow, so if the ECMWF/GEM
solutions verify, we could see a widespread accumulation of several
inches of snow from the Genesee valley east, however confidence in
this remains low at this time - particularly given that the
precipitation associated with these strong coastal lows tends to be
focused more to the east of our forecast area.

Upper level ridging is progged to cross the area Tuesday night
before the next system, a classic Colorado low, kicks out of the
plains and across the Great Lakes. This can be expected to bring
another round of precipitation, likely in the form of snow changing
over to rain, to the forecast area on Wednesday, with precipitation
changing over to snow behind the low as colder air finally moves
back into the region Thursday. Current guidance continues to
indicate a pattern change, with longwave upper level troughing
shifting to the east, signaling a return to winter by the end of
next week going into next weekend.

&&

.AVIATION /09Z FRIDAY THROUGH TUESDAY/...
Low stratus will persist through early to mid morning across much of
the area, with IFR favored across higher terrain and MVFR at lower
elevations. The stratus will also intersect some of the higher hills
with fog across higher terrain.

The fog and low stratus will steadily erode later this morning from
south to north as southerly flow just off the deck increases, with
downslope winds helping to scour out the low level moisture. Rain
will arrive across the western Southern Tier by late morning or
midday as a mid level trough arrives. This area of rain will then
move northeast across the rest of Western and Central NY during the
afternoon and evening, weakening with time.

Expect a return to IFR during the afternoon across the higher
terrain of the western Southern Tier. MVFR/IFR conditions will then
become more widespread again tonight behind the departing mid level
trough, with abundant low level moisture supporting low stratus, fog,
and drizzle.

Outlook...

Saturday and Sunday...Areas of IFR/MVFR in low stratus, fog, and
drizzle.
Monday and Monday night...Areas of MVFR/IFR with rain changing to
wet snow.
Tuesday...Areas of MVFR/IFR with wet snow.

&&

.MARINE...
Winds and waves will remain relatively light at 15 knots or less
today through Saturday. A weak trough will cross the Lower Great
Lakes this afternoon and evening, followed by weak high pressure
late tonight and Saturday.

Northeast winds will begin to increase Sunday, and increase further
on Monday as low pressure deepens along the east coast and high
pressure builds east across Quebec.

&&

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

&&

$$

SYNOPSIS...HITCHCOCK
NEAR TERM...HITCHCOCK
SHORT TERM...WOOD
LONG TERM...WOOD
AVIATION...HITCHCOCK
MARINE...HITCHCOCK


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