Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 220027
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
727 PM EST Tue Feb 21 2017

.SYNOPSIS...
A weak frontal boundary will push across our region this evening
with some shower activity...then fair weather will return for
Wednesday and Thursday. Temperatures will remain well above normal
through the end of the work week...particularly on Friday when parts
of the region will flirt with 70 degrees. A strong cold front will
cross the area late Friday night with notably colder weather
returning for much of the weekend.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
At 7pm, an elevated frontal boundary extended from the North
Country to the Southern Tier of NYS. While this was a solid line
just a couple hours ago, it has weakened considerably,
especially along the southern portions of the line. Model
consensus generally captures this boundary, but most guidance
was just a tad slow with showers now expected to end across most
of Western New York in the next hour or two with just spotty
shower activity after this. Otherwise, patchy fog may develop
tonight with the residual low moisture and potential mixing with
the cooler lake waters or snow pack. Cloud cover should remain
fairly solid, but any clearing would also result in fog.
Temperatures tonight will remain well above freezing...with mins
ranging from the mid- upper 30s to the mid 40s over the west.

While a fair amount of the mid level moisture will move out of the
area on Wednesday...there will still be near saturated conditions
below 6k ft. This will retard the speed of the clearing...with local
lift from orographics possibly leading to some morning sprinkles.
Otherwise...it will be a very mild day with the mercury climbing to
the lower 60s across the bulk of western New York and into the lower
50s across the North Country.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
Well above normal temperatures will continue through the second half
of the week ahead of a storm system which will arrive by Saturday.
Southerly flow wrapping around a Bermuda High and ahead of a
developing storm system over the central portion of the county will
boost temperatures about 20 degrees above normal on Thursday and 30
or more degrees above normal on Friday. Readings on Friday will run
very close if not break record High Temperatures.

Outside of the warm temperatures chances for showers and eventually
maybe even a thunderstorm will mainly reside along passing frontal
boundaries. On Wednesday night, a southwesterly low level flow will
develop ahead of a weak low pressure system passing north of the
Great Lakes. Very weak warm advection and synoptic lift aloft will
introduce a chance of a shower ahead of a weak cold front trailing
the surface low. The front will approach western NY Wednesday night
then cross the forecast area on Thursday with mainly a chance for
some scattered showers. Temperatures as mentioned above will run
above normal with lows only slipping back into the 40s Wednesday
night then rising into the 50s on Thursday ahead of this front with
the best chance for some low 60s across the Finger Lakes.

High pressure will the ridge south across much of the forecast area
on Thursday night behind the cold front with only a chance of a
shower toward the PA border where the cold front may stall. On
Friday and Friday night the Central Plains storm system will lift
toward the western Great Lakes. A warm front ahead of this system
will cross western and central NY during the day with likely POPs for
rain showers. 850mb temps then rise to near +10C in the wake of the
warm front where surface highs will make a run toward the 60s and
even 70 in a few spots. A few of the SREF members even show a high
warmer than 70 for Buffalo on Friday. Have gone just shy of 70 for
Buffalo and Rochester and just shy of 60 in Watertown. These
forecast highs would break a record in Buffalo and Watertown and run
just short of a record high in Rochester if verified. Southerly
winds will be a bit breezy but any stronger winds aloft will hold
off until behind the cold front on Saturday. There could also be a
slight chance of a thunderstorm on Friday afternoon/evening as the
12z GFS shows some weak surface CAPE and negative LIs working over
western NY in the warm sector ahead of the cold front. Temps Friday
night will run very mild ahead of the cold front only dipping down
into the upper 40s if not low 50s.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
On Saturday...a strengthening cutter-type low initially over the
Michigan Straits will continue to deepen to below 990mb as it tracks
northeastward into Quebec province...while swinging its trailing
cold front eastward across New York State. The 12z guidance suite
has trended a bit slower with the movement of the low and the passage
of its trailing cold front...with a general model consensus roughly
supporting a morning to early afternoon frontal passage south of
Lake Ontario...and an early to mid afternoon fropa across the North
Country. Nonetheless...the combination of deep/plentiful moisture
and strong large-scale forcing along and just ahead of the front
will remain plenty sufficient to support a band of moderate to heavy
showers crossing the region from west to east in conjunction with
the frontal passage...with some embedded thunder also remaining
possible given the presence of weak instability and the strong lift
along the boundary. Given 925-850 mb winds of anywhere from 40-60
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.

With the now-slower timing of the front...warmer temperatures will
also linger at least into Saturday morning areawide...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 (where the front will arrive
last)...it is possible that daytime highs could even reach into
the 60s depending upon the exact timing of the front and its
showers.

In the wake of the front...expect that rain showers should largely
break off for at least a time Saturday afternoon/evening as strong
subsidence and associated dry slotting works across the region in
its wake...before the combination of increasing wraparound moisture/
upsloping/continued cooling of our airmass leads to the development
of at least some lake effect snow showers east of the lakes during
the course of Saturday night. With a secondary swath 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. Temperature-wise...expect
readings to tumble back into the mid and upper 20s areawide 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.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
Showers resulting from a mid-level wave should generally remain
in the VFR category, with lower cigs behind the wave later this
evening. Expect these initially fall just above the MVFR/VFR
threshold this evening, but then lower later tonight as low
level moisture increases. Patchy IFR conditions will develop
late tonight and into Wednesday morning, with these most likely
at BUF/JHW, but hard to completely rule out at any TAF
location.


On Wednesday there will be some drying with diurnal heating
helping to lift cigs and dissipate any fog. Cloud cover will
still linger, with a mix of VFR/MVFR conditions by Wednesday
afternoon.

Outlook...

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.

&&

.MARINE...
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 tonight through
Wednesday night.

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.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...None.

&&

$$

SYNOPSIS...RSH
NEAR TERM...APFFEL/RSH
SHORT TERM...SMITH
LONG TERM...JJR
AVIATION...APFFEL/RSH
MARINE...RSH



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