Area Forecast Discussion
Issued by NWS Buffalo, NY

Home | Current Version | Previous Version | Text Only | 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
FXUS61 KBUF 022040

Area Forecast Discussion
National Weather Service Buffalo NY
340 PM EST Fri Dec 2 2016

Cold air will continue to flow across the Lower Great Lakes through
the end of the week. This will result in lake effect rain and snow
showers persisting east and southeast of Lakes Erie and Ontario
right through Saturday...before falling apart Saturday night and
Sunday as high pressure builds across New York State.


Water Vapor imagery displays an upper level low over Quebec/Northern
Maine, with a shortwave trough extending back across southern Quebec
and southern Ontario. Regional radars display a weak band of lake
effect snow/rain across the Southern Tier, while east of Lake
Ontario a band of greater lake effect precipitation is ongoing. To
the north of the band of precipitation, an area of precipitation is
expanding from Canada and towards the SLV and Lk Ontario, this on
synoptic lift ahead of the upper level shortwave.

Tonight as the upper level shortwave tracks across the Northeast,
expect this area of precipitation to push southward, pushing the
Lake Ontario band of lake effect precipitation, and to a smaller
degree, the Lake Erie lake effect precipitation southward as well.
Thermal profiles continue to be marginal for snow, with just a few
inches of snow accumulating tonight across the Tug Hill, and higher
terrain of SW NYS.

In addition to the lake effect snow, this upper level shortwave will
bring chances for precipitation across the region tonight. Any snow
accumulation outside of the lake effect snows will be very minor.

Tomorrow moisture in the lower levels, and within the favorable snow
growth zone will begin to wane, and we should see a diminishment to
lake effect precipitation, which will now be southeast of the lakes
on a northwest flow. As with this event as a whole, temperatures are
marginal, with a mix of rain and snow expected, and little snow
accumulation, perhaps an inch or so across the western So. Tier
hills tops and the Tug Hill region. As both the upper level low and
surface low exit towards the Atlantic Canada region, northwest winds
tomorrow will not be as strong as Friday.

Temperatures tonight will drop to around freezing across higher
terrain, while across the lake plain lows will remain in the mid
30s. Tomorrow highs will rebound slightly, back into the mid 30s to
lower 40s.


Nuisance lingering lake effect showers will wind down Saturday night
into early Sunday morning. The large surface high will advance to
the east across the Lower Great Lakes Saturday night. This will
further strengthen the lowering subsidence based cap and essentially
squash the remaining lake effect rain and limited snow showers. will be partly to mostly cloudy and uneventful.

On Sunday...the axis of the surface high will cross our forecast
area. We should experience at least some breaks of sunshine...
although temperatures will be similar to those of Saturday with
afternoon mercury readings in the 30s to lower 40s.

Conditions will deteriorate Sunday night as a negatively tilted the process of shearing out...will sweep northeast
across all of the Great Lakes region. While there will be some
lift provided by a diffluent upper level flow...the overall dynamics
with this feature do not look very impressive. Nonetheless, expect
light precipitation to overspread the region, mainly in the form of
snow. A light coating is possible across the lake plains, mainly on
grassy surfaces due to marginal surface temperatures, with up to 1
to 2 inches across the higher terrain where surface temperatures
will remain below freezing.

As the shearing trough pushes away to our northeast on Monday...
drier mid level air will arrive in its wake while ridging will
become re-established over the region. This will encourage the light
snow from the previous night to taper off and end as a mix of rain
and wet snow showers by midday. While not significant...the mixed
showers will linger a bit longer east of both lakes due to a little
lake enhancement. Daytime snow accumulations will be unlikely.

Tuesday will provide a brief break in the weather as high pressure
moves into Quebec, allowing for a mostly dry day. However, the next
approaching shortwave trough in the southwesterly flow will bring
another chance of rain by late in the day Tuesday.


A significant pattern change will take place across North America
during the second half of next week, which will deliver much colder
air into the Great Lakes and New England and possibly set the stage
for a significant lake effect snow event.

A parade of strong synoptic systems moving east through the Pacific
wave train will amplify the pattern across the North Pacific through
the weekend. This will in turn force a ridge to develop over western
North America for the second half of next week, allowing a deep
trough to carve out over the Great Lakes. The developing trough will
capture a large piece of cold Canadian air and circulate it through
the Great Lakes region by late next week.

Looking at the details...

Tuesday night a southern stream trough will move quickly through the
Ohio Valley and Northeast States. Warm advection ahead of the trough
will warm the low and mid levels enough to allow much of this to
fall as rain across lower elevations, although some wet snow may mix
in across higher terrain and the North Country. Most of this will
end by Wednesday morning as a dry slot moves into the area, although
a few widely scattered showers cannot be ruled out as a secondary
cold front crosses the area.

Wednesday night through Friday the mid level trough will become
established across the Great Lakes with cold air flooding into the
region. While the large scale pattern has been consistent in model
guidance over the past few days, the synoptic details and timing are
anything but clear with significant run to run differences. The 12Z
GFS remains faster in bringing the cold air in, with lake effect
developing east of the lakes as early as Wednesday Night. The ECMWF
is slower, bringing a wave of low pressure northward along the east
coast Thursday. This may produce some light wet snow or rain across
our region, and would delay any lake effect until Thursday night, a
full 24 hours later than the GFS. The ECMWF solution would also
result in a more northwest flow regime by the time the air is cold
enough to support lake effect.

The significant model differences on the synoptic scale evolution,
and the fact that this event is still a week away, still bring
plenty of uncertainty with respect to placement and intensity of
lake effect snow. That said, the upper air pattern supports the
potential for a significant event. CIPS extended analogs based on
the GEFS ensembles are returning a number of dates which had
significant lake effect snow downwind of Lakes Erie and Ontario, and
the pattern matches closely to some of our own analogs for
significant events developed through local research at NWS BUF. With
that in mind we have outlined the potential in the HWO. Stay tuned...


For the 18Z TAFs lake effect rain/snow has continued to drop
southward, now impacting the So. Tier of NYS including the KJHW
terminal. Activity here is broken in nature, likely lingering IFR
flight conditions for a few hours before an improvement back to MVFR

East of Lake Ontario the band of precipitation has dropped well
south of the KART airport. Additional precipitation, this ahead of
an upper level shortwave is nearing the SLV, and will continue to
drop southward across not only the KART airfield, but also the
remaining 4 TAF sites this evening and early overnight.

After this activity pushes through, it will leave lake effect snow
in a weakened state, with mainly MVFR/VFR flight conditions across
the region for the last 6 to 12 hours of the TAF cycle.


Saturday afternoon through Sunday...Mainly VFR with
gradually diminishing lake effect rain/snow showers and attendant
areas of MVFR/IFR southeast of the lakes.

Monday...MVFR with a chance of rain and snow showers.

Tuesday and Wednesday...VFR with a chance of mainly rain showers.


A brisk westerly flow will veer to northwesterly tonight as an upper
level shortwave drops across the Northeast. Winds will be at their
strongest this afternoon and evening before diminishing tonight and
tomorrow with the weakening surface low over Atlantic Canada. Small
craft advisories will continue as is for the lakes, and Upper Niagara


MARINE...Small Craft Advisory until 7 PM EST Saturday for LEZ040-041.
         Small Craft Advisory until 10 PM EST this evening for
         Small Craft Advisory until 4 AM EST Sunday for
         Small Craft Advisory until 7 PM EST Saturday for LOZ042.



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