Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 180243

Area Forecast Discussion
National Weather Service Buffalo NY
943 PM EST Wed Jan 17 2018

Periods of light to moderate lake effect snow will continue through
Thursday east and northeast of the lakes before high pressure and
milder air allows the lake effect snow to end by Friday. Another
January thaw will arrive this weekend with above normal temperatures
for several days. A cold front will cross the area late Monday and
Monday night with rain showers. Colder temperatures will return by
Tuesday following this cold front.


The main concern through the near term period will continue to be
lake effect snow.

Off Lake Erie...

The extensive ice cover did little this past afternoon to limit the
lake effect process. Satellite imagery showed multiple streamers of
light to moderate lake snow coming right off the icepack in the
central basin of the lake. The ice appears fairly thin in this area.
There can still be sensible heat flux through thin ice, but not
latent heat flux or moisture flux. There is a small patch of open
water between Chautauqua County and Long Point over the deepest part
of the lake, which is adding some moisture.

The limiting inversion height was in the vicinity of 6k ft
late this past afternoon...but tonight that will lower to under
5k feet...and this will effectively eliminate the snow crystal
growth area. While this temporarily brought an end to the lake
snows...subtle changes to the thermal profile will encourage the
snows to become re-established by daybreak.

By Thursday morning, forecast BUFKIT soundings show the inversion
growing a little higher again to about 5K feet. More importantly,
the layer beneath this moistens again with a favorable dendritic
growth zone developing again. This may allow some lake effect snow
to re-develop, focused on the Buffalo Metro Area. Mesoscale models
are for the most part showing little or nothing, but then again,
that was the case today as well. The model guidance is likely not
handling the impacts of thin ice cover appropriately. Given the
return of marginal conditions, increased POPS to likely with 1-2
inches of accumulation for Thursday near Buffalo.

Off Lake Ontario...

Radar imagery shows a broad area of lake enhanced snow across much
of the region east of the lake, with more pure lake effect snow
developing over the lake. Periods of snow will continue overnight
from the Tug Hill northward across much of Jefferson County, with
another 2-4 inches likely in persistent snows. The high shear
environment is forcing a wider area of snow than normal. Overnight
the inversion will lower here as well with less favorable dendritic
crystal growth. This should allow the lake effect snow to weaken for
a time, with boundary layer flow becoming southwest and carrying
what remains into mainly Jefferson County and the northern Tug Hill.
Expect any additional accumulations from late evening on to be very

By early Thursday morning conditions become slightly more favorable
again as lake induced equilibrium levels rise to around 6K feet, and
the layer of dentritic crystal growth grows deeper and more
saturated beneath this inversion. This should allow for an uptick in
lake effect snow intensity again Thursday. Boundary layer flow also
veers more westerly, centering the band on the Tug Hill region.
Mesoscale model guidance is making a little better attempt at
picking up on this, but still may be underdone. Expect additional
accumulations of 3-5 inches on Thursday across the Tug Hill, and 2-3
inches across the surrounding lower elevations.


Southwest winds will increase through Thursday as a 40-45 knot
southwesterly low level jet crosses the region. The strongest winds
will be from the Lake Erie shore northeast across the Niagara
Frontier, where gusts to 40 mph are likely. This will produce areas
of blowing and drifting snow, even in areas where it is not snowing.
Outside of this area, expect gusts of 20-30 mph with some limited
drifting snow in open areas.


Expect temperatures to be fairly steady tonight given the wind and
mechanical mixing. Expect mid to upper teens on the lake plains and
lower teens for the interior. Highs on Thursday will be in the mid
20s in most areas.


Thursday night, a compact but robust 500 mb shortwave in the
northwesterly flow aloft will track across Lake Ontario. This will
both spread some generic widespread snow showers across the region
with light accumulations of a tenth to a half inch, as well as
enhance the the marginal lake effect snow east of Lake Ontario, with
up to an additional 3 inches possible over the northern Tug Hill.
This lake enhancement will linger into Friday morning, before
diminishing through the day Friday as drier and warmer air builds in
aloft with rising heights behind the departing wave. Outside of this
limited lake effect, expect mainly dry weather Friday. Temperatures
will begin to moderate on Friday as broad zonal flow stretches
across the eastern CONUS, with most locations seeing a high with in
a few degrees either side of the freezing mark.

On Saturday, we will get caught in the middle between low pressure
moving through the Hudson Bay area to our north and high pressure
moving off the Southeast coast to our south. The result will be
breezy but dry conditions with gusts up to 45 mph possible,
especially northeast of the lakes, as the pressure gradient tightens.
This will also continue the moderating temperature trend with highs
pushing into the low 40s for many locations.


Fairly zonal, pacific influenced flow will be in place across the
CONUS on Sunday, as a trough exits from the Four Corners region. The
increasing southwesterly flow and rising heights aloft across the
forecast area ahead of the approaching trough will usher in warmer
temperatures from Sunday into Monday. High temperatures will run in
the 40s, both days, with perhaps a few locations near the 50 degree
mark by Monday. The only exception will be some 30s possibly
lingering in the North Country from a backdoor cold front as a
Canadian high pressure builds to our north. Expect to see a few
scattered showers develop in the vicinity of the warm front across
the region on Sunday into Sunday night along with ample cloud cover,
although it will not likely be a washout with plenty of dry time.
South of Lake Ontario, this would mainly be rain, with a mix of
either rain, freezing rain or snow for eastern Lake Ontario. An
approaching cold front Monday night, tied to the ejecting trough
moving from the central plains to the eastern Great Lakes, will
usher in widespread, soaking rain showers. There will be ample
moisture to work with as the trough taps into a rich subtropical
moisture source from the Gulf of Mexico. Cooler air will rush back
into the region with blustery southwest to west winds behind the
cold front passage, bringing a return to more seasonable
temperatures for mid-week along the potential for more lake effect


The nose of a large surface high will push across our forecast area
tonight...and while this will provide most areas with fair VFR
conditions...IFR to MVFR conditions in lake snow will be found east
of Lake Ontario. This will impact the KART and KGTB sites.
Intermittent MVFR cigs will also be present at KIAG.

Similar conditions will be found across our region on
Thursday...although renewed lake snows northeast of Lake Erie will
support MVFR to IFR conditions at KBUF. will become windy tonight and Thursday, with gusts of
35 knots northeast of Lake Erie, and 20-30 knots elsewhere. This
will result in some blowing snow.


Thursday night through Friday...localized MVFR to IFR possible in
scattered to occasionally more numerous lake effect snow showers
east of the lakes...with mainly VFR conditions elsewhere.
Saturday and Sunday...Mainly VFR.
Monday...Mainly VFR with a chance of rain late.


Moderate to strong westerlies will continue through Thursday on
Lakes Erie and Ontario with a strong pressure gradient between low
pressure over northern Quebec, and high pressure over the southeast
states. This will bring high end Small Craft Advisory conditions to
both lakes through Thursday. The windy conditions are likely to last
into Saturday before finally diminishing on Sunday.


NY...Winter Weather Advisory until 7 AM EST Friday for NYZ006>008.
MARINE...Small Craft Advisory until 10 PM EST Saturday for LEZ040-041.
         Small Craft Advisory until 4 AM EST Sunday for



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