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Area forecast discussion
National Weather Service Buffalo New York
925 am EST Tue Nov 12 2019

Synopsis...
lake effect snow will continue southeast of the lakes today through
early Wednesday with localized light to moderate accumulations. A
weak trough will bring a few snow showers Thursday with minor
accumulations possible. The well below normal temperatures will
continue through the end of the week before warmer weather arrives
next week.

&&

Near term /through tonight/...
regional radars show the synoptic snow has ended as of mid morning.
What remains is lake enhanced upslope flow driven by northwest flow.
This will produce some additional light snow through the rest of the
morning. Additional accumulations today will generally be less than
an inch, with up to 2 inches locally along the Chautauqua ridge and
from Wayne to Oswego counties. All of the winter storm warnings have
now been dropped.

Attention shifts to lake effect potential going forward today
and tonight, acknowledging the favorable over-lake thermodynamic
environment evolving within this unseasonably cold profile. The
mean flow will tend to back with time, seemingly favoring an
eventual northwest flow regime. This process may very well offer
the opportunity for some localized accumulation today and
continuing tonight.

Despite the favorable thermodynamics and thus strong instability,
the arriving airmass is rather dry. The dry airmass and
unfavorable, short northwest fetch will limit the lake response
to some extent. Off Lake Erie, persistent upslope flow off the
lake will contribute to occasional snow showers across the
higher terrain of inland Chautauqua County and western
Cattaraugus County. This may add a few more inches locally
during the day today, then possibly a few more inches tonight.
Lake effect southeast of Lake Ontario will also produce a few
additional inches from Wayne to Oswego counties today, mostly
this morning while some synoptic scale moisture is still in
play. By tonight, hi-res guidance is suggesting more organized
lake effect developing with an upstream connection to Georgian
Bay which will likely focus a band capable of producing several
inches of new snow from northeast Monroe County through
Southwest Oswego County.

&&

Short term /Wednesday through Friday night/...
a very cold airmass will remain across the eastern Great Lakes
Wednesday. Over the course of the day, a mid-level ridge axis will
slowly track across the region and warm air advection will move into
western New York. Temperatures at 850mb will range from -8c across the
western southern tier to -13c across the Tug Hill region by
Wednesday afternoon. Daytime highs will only reach the low 20s east
of Lake Ontario to the mid to upper 20s across western New York. Lake
effect snow showers will be ongoing southeast of Lake Erie and Lake
Ontario Wednesday morning. Surface high pressure will track into the
region through the day and snow showers will taper off while moving
northward into the late afternoon. Snowfall amounts of an inch or
less are expected Wednesday.

High pressure quickly moves off the New England coast while warm air
advection occurs aloft Wednesday night. Even with southerly winds
increasing to 10-15 mph over night, overnight lows will fall to the
low teens east of Lake Ontario to the upper teens to low 20s. Wind
chills will be in the single digits to low teens. Dry conditions
will last through Wednesday night as the next shortwave trough
tracks across the mid-west. This mid-level feature will increase
moisture and cold air advection will move back into the eastern
Great Lakes by Thursday afternoon. A southwest flow ahead of a cold
front will favor lake enhanced snow showers northeast of Lake Erie
Thursday afternoon and northeast of Lake Ontario Thursday evening.
Winds will shift more westerly putting snow showers east of the
lakes Thursday night. The moisture tied with the shortwave trough
will quickly move to the east and therefore snow showers will be
lackluster even with lake induced instability present into Friday.
Snowfall amounts of 1-2 inches are possible Thursday afternoon-
Friday morning. Another cold front will approach the region from the
north Friday. Best forcing and moisture will be north of Lake
Ontario through the day with the chance of rain or snow showers east
of Lake Ontario through the afternoon.

There will be a slow warming trend Thursday and Friday with highs
back in the mid to upper 30s and overnight lows Thursday in the
upper 20s to low 30s.

&&

Long term /Saturday through Monday/...
in the long term portion of the forecast...strong high pressure will
crest across our region on Saturday. Its core will then slide eastward
to northern New England and the Canadian Maritimes on Sunday and remain
in place through Monday...with ridging still extending back across our
region through this period. This will result in mainly dry and uneventful
weather prevailing across our region this weekend and into early next week...
and more importantly one last day of well-below average temperatures on
Saturday giving way to a steady day-to-day warming trend for Sunday and
Monday as a southerly return flow of milder air develops on the backside
of the ridge axis. At this distant Vantage Point it appears that highs
in the mid 20s to lower 30s on Saturday will climb into the upper 30s
to mid 40s on Sunday...then to the mid and upper 40s on Monday...when
some portions of western New York could see readings approach or even
reach 50 degrees. Looking just beyond the end of the current forecast
period...this warming trend appears to be the beginning of a Switch Back
to a milder pattern that may last through most...if not all of next week.

&&

Aviation /15z Tuesday through Saturday/...
radar imagery showing light lake effect and upslope snow primarily
along the south shores of the lakes this morning. This will continue
to produce local IFR this morning.

Visibility will improve to VFR in most locations by late morning as the
snow ends. Some limited lake effect snow will develop southeast of
the lakes. Off Lake Erie, this may impact kjhw at times. Off Lake
Ontario, most of the snow will focus near or just southwest of kfzy.
Ceilings will improve to MVFR in the morning, with VFR outside of lake
effect areas in the afternoon.

Outlook...

Tuesday night and Wednesday...VFR/MVFR. A chance of snow showers.
Localized lake effect snow and IFR southeast of the lakes.
Thursday...MVFR/IFR with a chance of snow showers, especially east
of the lakes.
Friday and Saturday...VFR.

&&

Marine...
on Lake Ontario, moderate northwest winds will continue today into
tonight, supporting Small Craft Advisory conditions through tonight.
On Lake Erie, the northwest winds will diminish temporarily today,
but will increase again by this evening and continue through
tonight, producing additional Small Craft Advisory conditions.

High pressure will build into the eastern Great Lakes by Wednesday,
providing a brief period of lighter winds. Another trough will cross
the eastern Great Lakes Thursday, which may produce the next round
of Small Craft Advisory conditions as southwest winds increase.

&&

Climate...
a frigid airmass (for this time of year) will pass over the
region through midweek. The shot of sub Arctic air will support
near-record to record cold temperatures. Below are the record
low maximum temperature and record low minimum temperature for
our three climate sites of Buffalo, Rochester and Watertown
for November 12th-13th.

City.......record low maximum (year)...record low minimum (year)

Tuesday November 12

Buffalo..........31f (1983)............22f (1921)
Rochester........32f (1983)............21f (1983)
Watertown........32f (2013)............15f (1997)

Wednesday November 13

Buffalo..........24f (1911)............16f (1986)
Rochester........23f (1911)............17f (2013)
Watertown........24f (1983)............11f (1997)

&&

Buf watches/warnings/advisories...
New York...none.
Marine...Small Craft Advisory until 10 am EST Wednesday for lez040-041.
Small Craft Advisory until 10 am EST Wednesday for
loz043-044.
Small Craft Advisory until 1 am EST Wednesday for loz042.
Small Craft Advisory until 7 am EST Wednesday for loz045.

&&

$$

Synopsis...Hitchcock/tma
near term...Hitchcock/tma/zaff
short term...hsk

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