Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 150012

Area Forecast Discussion
National Weather Service Buffalo NY
712 PM EST Sat Jan 14 2017

High pressure will remain in control of the Lower Great Lakes region
through Monday with dry weather most of the time with the exception
of a few scattered light snow showers southeast of Lake Ontario late
tonight and Sunday morning. Low pressure will then move through the
Great Lakes Tuesday and spread more rain into the region. The rain
may begin as a brief period of freezing rain prior to the arrival of
much warmer air.


A frontal wave will continue to move east through the Mid Atlantic
States through this evening. Extensive mid level clouds over the
bulk of the region early this evening will clear from west to east
the frontal wave moves off the east coast.

After midnight a weak cold front will drop southeast across New
England, with the western tail end dropping south across Lake
Ontario and into Western and Central NY late tonight and early
Sunday morning. A shallow but fairly extensive field of low level
moisture will move south out of Ontario and into our region late
tonight and early Sunday morning, producing a period of widespread
low stratus with an assist from lake effect clouds and upslope flow.
This will bring a good deal of cloud cover from late tonight through
at least the first half of Sunday.

In addition to the clouds, a slightly cooler airmass behind the cold
front and better moisture will support some very limited lake
response southeast of Lake Ontario. Lake induced equilibrium levels
only rise to 4-5K feet, and temperatures beneath the inversion will
not support much dendritic crystal growth. With that in mind, expect
just a few scattered light snow showers southeast of Lake Ontario
late tonight and Sunday morning. This will produce a dusting in a
few spots from Monroe to Oswego counties. Some weak upslope may also
produce a light dusting in the western foothills of the Adirondacks.

The weak lake effect will end by early afternoon Sunday as the
inversion lowers further. The extensive stratus should begin to
erode from the edges, with at least partial clearing developing
later in the day.

Temperatures will remain very close to seasonal normals for mid
winter. Expect lows in the lower to mid 20s on the lake plains
tonight and teens across the interior Southern Tier and North
Country. Highs on Sunday will be in the upper 20s to lower 30s on
the lake plains and mid 20s higher terrain and North Country.


Sunday night, high pressure will move nearly directly overhead
before settling off the Mid-Atlantic coast during the day Monday.
This will produce a cool and dry night Sunday night, as radiational
cooling is optimized in interior valleys with light winds and clear
skies. Light southerly winds will pick across the lake plains later
Sunday night as the high pressure moves eastward, thus limiting
ideal radiational cooling there. The result with be lows in the
teens in interior locations, with low 20s in the lake plains. On
Monday, temperatures will start to recover with return flow
developing and rising heights aloft under the upper level ridging.
Most locations will be above freezing on Monday, with highs in the
upper 30s. Mid and high level cloud cover will begin to increase
across southwestern portions of the forecast area by late Monday
ahead of an approaching warm front and our next storm system.

A southern stream shortwave, currently near the Baja California,
will track toward the Great Lakes by Monday night into Tuesday,
while a northern stream shortwave dives in from the northwest. This
complex low pressure system will track a surface low just northwest
of the forecast area, before a secondary surface develops near the
New England coast by Wednesday. Looking more closely at the details,
weak high pressure to our east will keep shallow cold air locked in
near the surface on an easterly wind Monday night while warm
advection aloft pushes the temperature profile above freezing off
the surface. The result will be a chance for freezing rain as the
initial precipitation overspreads the region from southwest to
northeast late Monday night into Tuesday morning. Confidence in
freezing rain remains poor at this point as the surface high is
fairly weak and displaced well northeast of the area into Quebec.
However, the typical interior valleys of the Southern Tier and the
Saint Lawrence / Black River valley may be slow the warm, and thus
will remain most prone to seeing any freezing rain for a brief
period at the onset of precipitation. Also, as is typically the
case, this initial precipitation will have to overcome fairly dry
air near the surface to even make it to the ground. Thus, if
freezing rain were to develop, any accumulations would likely be
only a trace to a few hundredths of an inch. Will continue to
mention the potential in the HWO.

Much warmer air surges into the region on Tuesday as the main
surface low tracks to our west and we get into the warm sector.
Temperatures will make it into the 40s most locations, with perhaps a
few interior valleys and locations along the Saint Lawrence not
making it out of the 30s. Downslope winds off the Chautauqua ridge
on southeasterly flow may even push temperatures at Dunkirk to near
50 if there is enough break in the precipitation. Speaking of
downslope winds off the Chautauqua ridge, expect it to get quite
windy with gusts to 40 mph Tuesday morning, before the flow turns
southwesterly. The bulk of the rainfall will move through during the
day Tuesday and into Tuesday night, with most locations picking up a
quarter to half an inch of rainfall. Enough cold air behind the
front may change the rain showers over to some wet snow across the
Tug Hill Region late Tuesday night...though much of the region will
likely still be in the mid to upper 30s at dawn Wednesday.

Wednesday itself will feature cooler (but still notably above
normal) temperatures...with daytime highs generally averaging out
within a few degrees either side of 40. Otherwise fairly extensive
wraparound moisture in the wake of the surface low will keep
widespread cloud cover across our region along with some spotty
lingering rain and wet snow...with the latter largely confined to
the higher terrain.


The main story during this period will be continued above normal an initially quasi-zonal flow in the wake of the
midweek system will give way to building large-scale ridging across
our region by the end of the week. Expect daytime highs mostly in
the lower to mid 40s Thursday to steadily warm to the 45-50 range
by the end of the period...while nighttime lows will fail to drop
below the 30s.

With respect to precipitation chances...leftover scattered rain
and snow showers across our region at the start of the period will
gradually wind down Wednesday night and Thursday morning as the
supporting area of wraparound moisture gets stripped away and modest
surface-based ridging builds in from the Ohio Valley. After that...
mainly dry weather is expected for the balance of the period with
our region largely under the influence of building ridging both at
the surface and aloft.


Fairly extensive alto-cu south of Lake Ontario at 00z will at least
partially clear from the northwest by 03-04z. The widespread VFR
conditions will then persist until about 08z when a stratus deck
will build in behind a weak backdoor front.

This will result in widespread MVFR CIGS late tonight and the first
half of Sunday, with some IFR possible across higher terrain. The
low stratus will gradually scatter out Sunday afternoon with a
return to mainly VFR.

A few light scattered lake effect snow showers will develop late
tonight and Sunday morning southeast of Lake Ontario as the airmass
grows marginally supportive of lake effect. This should remain very
light, with mainly VFR and spotty MVFR VSBY between KROC and KFZY.


Monday...Mainly VFR.
Tuesday...MVFR/IFR with rain likely. Rain may begin as a brief
period of freezing rain.
Wednesday...VFR/MVFR with a chance of rain and snow showers.
Thursday...Mainly VFR.


High pressure will drift east off the east coast tonight. A weak
cold front will drop southeast across New England tonight, with the
western tail end crossing Lake Ontario. West to northwest flow will
increase along and behind the cold front, and produce a round of
Small Craft Advisory conditions on the east half of Lake Ontario
late tonight and Sunday morning. Winds will then diminish Sunday
afternoon through Monday as high pressure builds back into the Lower
Great Lakes.


Flooding remains along the Allegheny River. Salamanca dropped below
flood stage early this morning, but Olean remains above flood
stage after cresting late Friday. Olean will continue to slowly
fall today, dropping below flood stage on Sunday.


The main story for next week and beyond will be the extended
period of above normal temperatures not only in our region, but
for much of the eastern 2/3 of the nation. Over the next two
weeks, a strong closed low will remain parked over the Bering
Straits, forcing a strong Pacific East Asian jet to extend farther
east than normal. This will continue to bring a parade of Pacific
systems into the western United States, while also supporting
zonal flow and a flat ridge downstream across the central and
eastern part of the country. The westerly flow across the
continent will support strong Chinook warming off the Rockies,
with warmth spreading to the east coast and even well north into
southern and central Canada.

The warmth will last for another 12 days or so, but there is a
significant pattern change brewing beyond that. A Sudden
Stratospheric Warming event has just occurred in the northern
hemisphere. These events occur when planetary waves propagate
vertically into the stratosphere, with wave breaking and dampening
processes acting to rapidly warm the stratosphere over the high
latitudes and greatly distort the Stratospheric Polar Vortex.

This warming and disruption in the stratosphere has been shown in
numerous studies to slowly feed back into the troposphere, with a
strong tendency for high latitude blocking to increase about 2
weeks after the warming takes place. High latitude blocking
increases the ability of polar air to spread southward into the
mid latitudes, and increases the chances of cold and wintry
weather locking in for a longer period of time.

It appears the long range guidance is beginning to capture this
idea, with the GEFS and NAEFS ensembles suggesting a more highly
amplified flow starting late this month, with a ridge developing
over Alaska and the West Coast while a deep longwave trough
begins to establish across central and eastern North America. The
developing ridge in Alaska may also promote a period of cross
polar flow, draining frigid Siberian air into northern Canada.
GEFS ensembles also support a more negative NAO and AO pattern
towards the end of the month. Putting all this together, it
appears the pattern should become much colder and more wintry
around January 25-27. Past stratospheric warming events suggest
this cold pattern may last for quite some time, and may support
the potential for periods of well below normal temperatures by the
end of the month and first half of February. Stay tuned.


MARINE...Small Craft Advisory from 1 AM to 1 PM EST Sunday for



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