Area Forecast Discussion
Issued by NWS Buffalo, NY

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000
FXUS61 KBUF 050126
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
826 PM EST Sun Dec 4 2016

.SYNOPSIS...
A mid-level trough will pass over the area overnight, producing a
several hour period of widespread light to moderate snow. A few
inches of snow accumulation can be expected with the highest amounts
over the higher elevations. Another surface high will bring a short
break from the unsettled conditions Monday afternoon and night
before our weather will become quite active for the remainder of the
week. This will include a trend towards wintry weather after
Wednesday when significant lake snows will impact areas east of both
lakes.

&&

.NEAR TERM /THROUGH MONDAY/...
...Winter Weather Advisory for the Eastern Lake Ontario Region...

An upstream trough is becoming negatively tilted while racing across
the Central Great Lakes this evening. Attendant strong surge of
isentropic lift collocated nicely with plume of deeper moisture,
both of which are set to slide through our area overnight bringing
widespread light to moderate snowfall.

East of Lake Ontario...
Have updated the forecast this evening to add a Winter Weather
Advisory for the eastern Lake Ontario region late overnight into
Monday morning. Have blended in some of the latest mesoscale QPF
guidance which seems to pick up on some enhanced lift focused east
of Lake Ontario overnight. This area aligns with the nose of an
850mb low level jet, low level frontogenesis and isentropic lift
leading to some higher snowfall amounts. There is also likely an
orographically component with southerly flow rising up over the
southern end of the Tug Hill. Expecting a general 2-4 inches of
general snow across Oswego, Jefferson and Lewis counties with 3-6
centered on the southern end of the Tug Hill from about Redfield
and Worth across Montague and Osceola to about Turin. BUFKIT
profiles for RME show a nice crosshair signature of moisture, lift
and snow growth from about 06z- 18z. Surface temperatures in the
low 20s should allow snow to stick and accumulate despite soil
temps in the mid 30s. Timing of the worst conditons including snow
covered and slippery roads and reduced visibilities for this event
will also come during the morning commute complicating morning
travel to work and school.

Western New York and the Finger Lakes...
Thermal profiles are marginal to start with the 00z KBUF RAOB
showing dry and unstable environment through 850mb with a warm
advection associated inversion above 850mb. Surface temperatures
across western NY are still above freezing. First radar returns
over western NY should be just virga with dry low levels but
expect onset of precip to occur near 9-10pm in the western
counties. Initially expecting a rain/snow mix as precipitation
arrives into the west this evening. Magnitude of lift and cooling
through the melting process should transition all areas over to
snow rather quickly although lake modification may keep areas
right along the Lake Erie and Lake Ontario shorelines in a mixed
precipitation regime a but longer.

Mesoscale models similar in showing a rather quick moving system,
but given forcing and available moisture, hard to argue with
guidance blend QPF totals of around a quarter or so. Cooling thermal
profiles and strong support for periods of enhanced lift in the
dendritic growth layer suggests snow-to-liquid ratios pushing 12:1
values, especially for interior section. All in all, continuity
amounts of 1-3" snow totals still look reasonable for interior
western NY and the Finger Lakes. Probably no more than a coating to
an inch for the lower elevations along the lakeshore. The worst
conditons should be waning across western NY by the time the morning
commute is in full swing.

As we get in to Monday morning, the snow winds down from west to
east as forcing races off to the northeast. We may even see a brief
period of drizzle/freezing drizzle as mid level moisture departs.
Post-system airmass turns cold enough for some possible lake
contribution as winds turn northwest. Lake equilibrium levels remain
awfully shallow, suggesting any lingering lake effect snow showers
will remain light at best.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/...
Any lingering light snow/drizzle east of Lake Ontario Monday night
will end through the evening hours as lake inversion heights fall,
and moisture falls beneath the good snow dentritic growth zones.
Otherwise the night will be dry with some breaks in the clouds.

Tuesday will begin dry as a ridge of high pressure crosses the
region. A closed low seen over western Mexico Sunday afternoon will
open up as it races northeastward across the United States Monday
and Monday night. This feature will bring the next period of
unsettled weather through the midday hours Tuesday, and then into
Tuesday night. Given the source region of this shortwave within the
Southern Branch of the jet stream there will be more rain than snow
falling Tuesday, though through the night a few lower elevations
could see a mix of wet snow/rain in addition to the snow falling
over the higher terrain. Snow accumulations will be minor, with
again a general inch or two across higher terrain.

There may be lingering precipitation early Wednesday across the
region, and likely east of Lake Ontario where a moist, upslope flow
will maintain precipitation through the morning hours. A ridge of
high pressure extending across the Plains, will briefly extend
eastward towards the Eastern Great Lakes region, a spell a brief
period of dry weather before cold air advection under cyclonic flow
aloft, and moist westerly flow increases chances for light snow east
of the lakes later Wednesday night.

High temperatures will run a few degrees above normal, with
afternoon temperatures reaching the upper 30s to lower 40s Monday
and Tuesday. There will be no bitter cold this period with
overnight lows in the mid 20s to mid 30s.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
The period will feature cold temperatures with frequent opportunities
for snow. 12Z model guidance has trended away a potential
synoptic system, with a consensus now suggesting most of the snow
will be lake effect or at least lake enhanced. There is still
uncertainty in the wind direction and thus the location of lake
effect snow. There is the potential for significant snowfall,
especially considering the prolonged nature of the event which
runs Thursday through Saturday. Now for the details...

On Thursday a trough will dig across the Great Lakes region,
which will advect much colder air into Western New York. 850mb
temperatures will plummet and will average -12C to -14C across
the region Thursday night through Saturday. This will be cold
enough to support lake effect snow, with precipitation changing to
all snow by Thursday afternoon. The cyclonic flow aloft will
provide ample moisture, with embedded shortwaves likely to provide
periodic enhancement. For Thursday and Thursday night, it appears
that a WNW flow will be predominant. This may support banding east
or southeast of Lake Ontario, with less organized but persistent
bands off Lake Erie due to upsloping and moisture from Lake Huron.

On Friday and Friday night, predominantly a NW flow is expected,
which would continue lake effect snows but push the steadiest
snows a bit southward. By Saturday the upper trough axis will
shift east of the New England coast, with a weak surface high
building behind it across the Great Lakes region. This should
bring in slightly drier air and lower equilibrium levels, but
conditions still support localized lake effect snows to continue.
Winds are forecast to veer to the southwest and eventually the
south by Sunday. This would lift what is left of lake effect snow
bands northeast of the lakes.

Although consensus agrees on the cold pattern, there is still a
considerable spread among model guidance in terms of specifics.
Even a subtle shift in winds would significantly impact the
location of the heaviest snows. This said, the pattern generally
favors the greatest amounts southeast of Lake Ontario (probably focused
near Oswego county) and the Western Southern Tier. It is still too
early for specific snowfall amounts and even these areas of focus
may change as new model guidance becomes available.

Otherwise, temperatures will be considerably colder than they have
been with highs on Friday and Saturday ranging from the mid 20s to
around freezing. The forecast favors a blend of raw model
guidance due to the wind and cloud cover which will limit daytime
heating and radiational cooling.

&&

.AVIATION /02Z MONDAY THROUGH FRIDAY/...
VFR cigs at 00z will deteriorate to MVFR with isolated IFR later
this evening with the arrival of a rain/snow mix changing over to
all light to moderate snow. This is associated with a disturbance
that will push northeast across the Lower Great Lakes. The snow will
likely reduce vsbys to IFR levels at all sites for a period of
several hours after 02-03z in western NY and 06-07z for Central NY.

The disturbance will shift east of the area on Monday with snow and
associated worst conditons ending by 12z for western NY but holding
through the morning for central NY. MVFR level cigs will the linger
through the rest of Monday in the wake of the disturbance.

Outlook...

Monday night...MVFR cigs improving to VFR. Tuesday...Mainly VFR.
Tuesday night and Wednesday...VFR deteriorating to MVFR with some
rain becoming likely.
Thursday and Friday...MVFR/IFR with snow likely.

&&

.MARINE...
A disturbance with widespread light to moderate snow will push
across the region overnight, winds are not expected to notably
freshen until Monday when the gradient will temporarily tighten
between the exiting system and the next surface high. A period of
small craft advisories has been issued for the nearshore waters on
Lakes Erie and Ontario.

Winds and waves will subside with the arrival of another surface
high overnight Monday night.

While winds will freshen from the east on Tuesday, but they will
remain below small craft advisory levels as the higher waves will be
confined to Canadian waters.

Looking further ahead, a deep storm forecast to track across
James Bay late in the week may generate gale force winds over the
Lower Great Lakes Thursday night and Friday.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Winter Weather Advisory from 1 AM to 1 PM EST Monday for
     NYZ006>008.
MARINE...Small Craft Advisory from 4 AM to 7 PM EST Monday for LEZ040-
         041.
         Small Craft Advisory from 10 AM to 10 PM EST Monday
         for LOZ043-044.
         Small Craft Advisory from 7 AM to 7 PM EST Monday for
         LOZ042.
         Small Craft Advisory from 1 PM to 10 PM EST Monday for
         LOZ045.

&&

$$

SYNOPSIS...SMITH/TMA
NEAR TERM...SMITH/TMA
SHORT TERM...THOMAS
LONG TERM...APFFEL
AVIATION...SMITH/TMA
MARINE...SMITH/TMA


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