Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 221152

Area Forecast Discussion
National Weather Service Buffalo NY
652 AM EST Wed Feb 22 2017

The forecast area will be caught between a high pressure system off
the Mid-Atlantic and a low pressure system moving into the upper
Great Lakes today, and southern Quebec on Thursday. This will result
in continued above normal warmth with mainly fair weather.
Temperatures will soar to near all-time February records Friday,
some locations possibly eclipsing 70 degrees. A strong cold front
will cross the region late Friday night with notably colder weather
returning for the weekend.


Early this morning there is an expansive area of dense fog extending
from northern Arkansas to Michigan and across portions of southern
Ontario. This fog has developed on the western periphery of mid and
high level cloud cover associated with a low pressure system moving
into the southeast and a front boundary draped across southeast New
York. For much of the forecast area, mid and high level cloud cover
lingers in the wake of the frontal boundary, preventing much fog
formation. The main exception is Niagara Falls, were some patchy fog
has developed with some breaks in the cloud cover and light winds.
The lingering patchy fog near Buffalo and Niagara Falls should break
up with diurnal heating/mixing after sunrise.

Today, south to southwesterly winds will develop as high pressure
remains off the mid-Atlantic, and surface pressures fall across the
upper Great Lakes, and Ontario Province ahead of the developing low
pressure system. This will advect the moisture rich (50+ dewpoint)
pool of air in place across the Ohio valley up Lake Erie and across
western NY this afternoon and evening. Expect advection fog to
develop over Lake Erie today, which will likely impact portions of
the city this afternoon and evening some locally dense fog possible.
Otherwise, the southwesterly flow will promote some light warm
advection and downsloping. This will allow daytime highs to run
warmer than yesterday in most all locations. Highs in the Genesee
Valley (which may also see more sunshine) will top out in the mid
60s, with even some low to mid 50s possible all the way into the
North Country. The only exception may be near Buffalo, where the
developing southwesterly flow off the cool lake and potential fog
may keep temperatures on par with yesterday, which still in the mid
to upper 50s.

Tonight will be extremely mild, with overnight lows held up by cloud
cover and a moist airmass. Southwesterly winds will also increase as
the developing surface low and associated pressure falls track into
Ontario Province, keeping the steady warm advection and mixing in
place overnight. Temperatures across western NY will likely not fall
below 50 overnight, which is quite remarkable, as a low of 50
degrees would be 30 degrees warmer than the normal low temperature
and 15 degrees warmer than the normal HIGH temperature for this time
of year at Buffalo and Rochester! Even Watertown may not fall below
45, which is 33 degrees warmer than the normal low! With such a mild
and moist airmass in place, advection across both Lakes Erie and
Ontario may bring more widespread fog to the region overnight.


A weak cool front will cross the forecast area on Thursday, as a
shortwave embedded in the southwest flow aloft and associated weak
surface reflection passes just to the north of the Great Lakes.
Cannot rule out a few stray showers in the weak warm air advection
pattern, but forcing and moisture profiles do not look favorable for
any widespread shower activity. Temperatures again will run above
normal with highs Thursday warming into the 50s ahead of the front,
with the best potential for some lower 60s across the Finger Lakes

High pressure will briefly ridge south across much of the forecast
area Thursday night behind the cold front, with only a chance of a
lingering shower toward the Pennsylvania border where the frontal
boundary may stall.

Friday and Friday night, the west coast trough releases eastward and
cyclogenesis over the plains will result in a strong low that will
push through the Great Lakes. The lead warm frontal boundary will
lift through western and central New York during the day Friday with
a period of widespread showers. Model soundings continuing to
suggest the possibility of thunder as elevated instability and
steepening lapse rates develop between about 700-500 mb. This period
also looks to feature well above normal and potentially record
breaking temperatures for portions of the area. Latest guidance
still on par with western New York emerging into the warm sector as
the center of the low tracks well west of the region. Some areas
could potentially see temperatures break into the lower 70s.

Current model runs have the deepening surface low eventually
tracking northeastward into Quebec province by Saturday, while
driving its trailing cold front eastward across New York State. The
combination of deep moisture and strong large-scale forcing along
and just ahead of the front will support a band of moderate to heavy
showers crossing the region from west to east with the frontal
passage, with some embedded thunder also possible given the presence
of sufficient instability and the strong lift along the boundary.
Given 925-850 mb winds around 50 knots, it remains possible that
this line of showers could mix at least some of these stronger winds
down to the surface as it passes through our region.

Warm temperatures will linger at least into Saturday morning, when
most areas should see highs ranging through the 50s before beginning
a steady downward trend following the frontal passage. Across
portions of the Finger Lakes and North Country, it is possible that
daytime highs could even reach into the 60s depending upon the exact
timing of the front and its showers.

Behind the front, the showers should largely break off for at least
a time Saturday afternoon/evening as strong subsidence and
associated dry slotting works across the region, before the
combination of increasing wraparound moisture/upsloping and
continued cooling of our airmass leads to the development of some
lake effect snow showers east of the lakes during the course of
Saturday night.

With a secondary surge of stronger southwesterly flow aloft
developing across Lakes Erie and Ontario for a time Saturday
afternoon and evening, the strong subsidence and cold air advection
regime should also help to mix at least some of this down to the
surface. This will result in the potential for a period of advisory-
worthy winds from Chautauqua county northeastward across the Niagara
Frontier to the Greater Rochester area, and also across Jefferson
county east of Lake Ontario. Expect temperatures to fall back into
the mid and upper 20s Saturday night.


Following all of this...a general westerly flow of notably colder
air will continue across our region Sunday into Monday...with 850 mb
temps bottoming out somewhere between -11C and -15C Sunday and
Sunday night. After a week of unseasonable warmth...this will result
in temperatures running much closer to seasonal averages for the
second half of the weekend and the first day of the new work week...
when daytime highs will generally be in the 30s and nighttime lows
will range through the 20s. While the much colder airmass will also
continue to support the potential for some lake effect snow showers
east of the lakes...significant questions remain as to the exact
degree of background synoptic-scale moisture that will be available...
with potentially limited moisture and strong late season diurnal
effects both possibly acting to prevent a noteworthy lake response
for large chunks of this period. In any event...whatever lake effect
snow showers there are should tend to wind down by later Monday/
Monday evening as the axis of surface high pressure slides across
our region...and warm air advection commences aloft.

Looking further out into the last 24 hours of this period...mostly
dry weather Monday night should then give way to our next chance of
precipitation later Monday night and Tuesday as the next cutter system
works into the western and central Great Lakes...with temps also likely
climbing back to well above average levels on Tuesday as this system
advects warmer air back into our region.


IFR fog will linger at IAG through 13/14Z and break up with daytime
heating and mixing. Otherwise MVFR cigs at ART will linger through
this afternoon, before seeing some improvement to VFR as southerly
winds develop and downslope the terminal.

Outside of these areas, expect VFR conditions this morning. Then
this afternoon more moisture rich and mild air will move into the
region on developing southwesterly flow. This will bring some
advection fog off Lake Erie close to IAG/BUF late this afternoon and
evening, then KART off Lake Ontario overnight. Tonight, this
abnormally warm and moist airmass will support some patchy IFR fog.


Thursday...Mainly VFR.
Friday and Saturday...Periods of rain showers with MVFR and
local IFR. Windy on Saturday.
Sunday...Mainly VFR but IFR to MVFR in lake effect snow
southeast of both lakes.


A relatively weak pressure gradient with a neutral to warm temp
advective pattern will keep relatively light winds and manageable
waves in place across the Lower Great Lakes today.

The next real time of concern will be late Friday night and Saturday
when a powerful cold front will cross the Lower Great Lakes.
Strong...possibly gale force winds...will be found in the
wake of the front Saturday and Saturday night.





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