Area Forecast Discussion
Issued by NWS Buffalo, NY

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000
FXUS61 KBUF 010612
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
112 AM EST Thu Dec 1 2016

.SYNOPSIS...
A cold front will finish crossing the region overnight...with
showers tapering off. In its wake...a colder airmass will overspread
the region for the remainder of the week...with lake effect rain
showers east-northeast of the lakes Thursday shifting southward
and becoming mixed with snow for Thursday night and Friday.

&&

.NEAR TERM /THROUGH TODAY/...
As of 06z...the surface cold front itself is now in the process of
crossing the North Country...and should be clear of our area by
07z or so. A narrow band of moderate to heavy showers marks the
boundary...with lighter to moderate showers behind the front
extending back to about the Genesee Valley. All of this activity
will continue to translate eastward with the front and wind down
from west to east overnight. Late tonight...a progressively cooler
260 degree flow will begin to generate some lake effect rain
showers downwind of Lake Erie...with these initially focusing on
areas south of Buffalo.

Temperatures at 850 hPa will lower to around -4C on Thursday which
should bring ample instability over a +8 to +10C lake waters to
produce a band of lake effect precipitation. The lower levels of
the atmosphere, and surface temperatures will remain too warm for
snow, such that just plain rain will fall from these lake plumes
later tonight and Thursday. An initial 240 to 250 wind flow will
bring these plumes to around Buffalo (Lake Erie)/Watertown (Lake
Ontario) before settling ever so slightly southward later Thursday.
The only exception is across higher terrain in the Western Southern
Tier where a few wet snowflakes may mix in on Thursday.

Temperature will remain mild this evening ahead of the cold front
with falling temperatures the second half of the night dropping down
into the lower to mid 40s. Under cold air advection aloft highs
Thursday will not be much warmer than their morning values, with
highs only rebounding a few degrees. This cold air advection will
also create brisk winds Thursday. Southwest winds will howl near the
lake shores, and especially the northeaster lake shores, with gusts
up to 40 mph. Inland southwest wind gusts will be lower, generally
25 to 35 mph.

&&

.SHORT TERM /TONIGHT THROUGH SUNDAY/...
Mid level closed low will cross Quebec and morph into an open wave
as it crosses into New England by Friday, eventually re-developing
over the Canadian Maritimes as energy transfers to the coast by
the weekend. There will be a series of minor shortwaves and their
associated surface troughs wrapping into western New York into the
first part of the weekend, resulting in periods of deeper
moisture and lake driven precipitation. Temperatures aloft will
gradually turn colder over this time with 850 mb temperatures
starting the period from -4/-5c, down to -7/-8c by Saturday. Low
level flow starts out westerly, slowly veering to northwest by
Saturday. This seasonably cool and moist cyclonic flow will
providing a favorable background for lake enhanced/effect
precipitation. Outside of the lake driven areas, occasional weak
ascent from passing subtle shortwaves will produce scattered light
showers, with the better coverage of these synoptic showers across
the North Country in closer proximity to better forcing and deeper
moisture.

Off Lake Erie...

The cooling boundary layer will allow for some wet snow to mix in
across higher terrain Thursday night into Friday, with a probable
change to all wet snow at times for the higher terrain. Expect a
slushy 1-2 inches of accumulation later Thursday night into Friday
morning across the high terrain of the Boston Hills and western
Wyoming County, and the hills of central and northern Chautauqua and
Cattaraugus counties.

Friday night and Saturday, the boundary layer will continue to cool
as boundary layer turn more northwest. This will push the lake
effect precipitation farther south into the Southern Tier. There
may be some additional minor accumulations across higher elevations.
Lake effect precipitation will then slowly diminish during the day
Saturday as a mid level ridge and somewhat drier air begin to build
into the Lower Great Lakes.

Off Lake Ontario...

The boundary layer will undergo modest cooling Thursday night which
will allow wet snow to mix in across the higher terrain of the Tug
Hill and western Adirondacks, with a probable change to all wet snow
late Thursday night through Friday across the highest elevations
where a 1-3 inch slushy accumulation is possible.

Friday night, the boundary layer will continue to cool as boundary
layer turn more northwest. This will push the lake effect
precipitation south and onshore from the Rochester area eastward
into the Finger Lakes. There may be some additional minor
accumulations across higher elevations.

On Saturday northwest flow will continue, with a spray of weak lake
effect showers southeast of the lake from near Rochester to Oswego
County.

Saturday night and Sunday, cool west northwest flow will remain in
place, supporting a few scattered rain and wet snow showers, and
some limited lake effect southeast of the Lakes. Temperatures will
be seasonable, with highs in the lower 40s at lower elevations and
mid to upper 30s across higher terrain.

&&

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
Model guidance begins to diverge by early next week, with
significant run to run differences noted in both the GFS and ECMWF
over the past few days. A weak trough is forecast to move northeast
across the area Sunday night and early Monday with a few wet snow
and rain showers possible from a combination of weak ascent from the
trough and a broad warm advection regime.

Monday night and Tuesday both the GFS and ECMWF show high pressure
back into the Ohio Valley and Lower Great Lakes. The mid continental
trough ejects a wave into the upper ridge, with strong southerly
warm advection, the ECMWF much more potent than GFS, but went with
withering PoPs for Tuesday and Wednesday and just chance PoPs, at
that. Note that the models have seemingly stretched the arrival
times of the next strong cold front and pattern change to wintry
conditions into the mid/end of the week.

Regardless of the synoptic details, the overall pattern suggests
a return to slightly above normal temperatures for Tuesday and
Wednesday, but an eventual arrival of wintry weather by the end
of the week.

&&

.AVIATION /06Z THURSDAY THROUGH MONDAY/...
As of 06z...the surface cold front is now in the process of
crossing the North Country...and should be clear of our area by
07z or so. A narrow band of moderate to heavy showers marks the
boundary...with lighter to moderate showers behind the front
extending back to about the Genesee Valley. All of this activity
will continue to translate eastward with the front and wind down
from west to east overnight. Late tonight...a progressively cooler
260 degree flow will begin to generate some lake effect rain
showers downwind of Lake Erie...with these initially focusing on
areas south of Buffalo. In general...general MVFR conditions
within the showers will tend to improve to the high MVFR/low VFR
ranges once the showers end overnight.

Thursday will be mostly cloudy, with lower (MVFR) cigs mainly
isolated to higher terrain or in lake effect rain showers. The
west-southwesterly flow will make these most likely at BUF and ART.

Thursday night...expect lake effect rain showers to shift southward
as the low level flow veers more westerly...while also becoming
mixed with snow showers. Expect MVFR/IFR within the lake effect
precipitation...with MVFR/VFR conditions prevailing elsewhere.

Outlook...
Friday through Sunday...Mainly VFR with areas of MVFR/IFR and
rain/snow showers east of the lakes.
Monday...MVFR with a chance of rain and snow.

&&

.MARINE...
In the wake of a cold front westerly winds will increase, nearing 30
knots on the lakes late tonight and through the day Thursday. These
winds will gradually diminish Friday and Friday night, but based
on the lastest forecast we have extended the small craft headlines
on the lakes as outlined below.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...Small Craft Advisory until 6 AM EST Saturday for LEZ040-041.
         Small Craft Advisory until 4 AM EST Friday for LEZ020.
         Small Craft Advisory until 1 AM EST Friday for LOZ030.
         Small Craft Advisory until 6 AM EST Saturday for
         LOZ043>045.
         Small Craft Advisory until 6 PM EST Friday for LOZ042.
         Small Craft Advisory until 1 AM EST Friday for SLZ022-
         024.

&&

$$

SYNOPSIS...JJR
NEAR TERM...APFFEL/JJR/THOMAS
SHORT TERM...TMA
LONG TERM...HITCHCOCK/WCH
AVIATION...JJR
MARINE...APFFEL/JJR/THOMAS



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