Area Forecast Discussion
Issued by NWS Buffalo, NY

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000
FXUS61 KBUF 221900
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
200 PM EST Wed Feb 22 2017

.SYNOPSIS...
Unseasonable warmth will continue through Saturday morning along
with a few passing showers.  Locally dense fog will also be a
possibility through Thursday, particularly near Lake Erie and Lake
Ontario. A strong cold front will move through Saturday.  This may
be preceded by some thunderstorms.  Following the front, expect
breezy to windy conditions, along with a return to some lake effect
snow east of the lakes by Sunday.

&&

.NEAR TERM /THROUGH THURSDAY/...
The jet that was responsible for the weekend pummeling over Southern
CA continues to stream eastward and will be responsible for the
development of two surface lows over the next two days.  The first
will be rather weak, and is already approaching the northern Great
Lakes region.  The 2nd low will mark then end of the warm spell when
it moves NE of WNY later Sat AM.  For the near term, we will follow
the first low as it continues east into Southern Ontario by Thursday
morning. The warm SW flow to the S of the low is not directly
tapping the Gulf or Atlantic due to an upper level low over the
Gulf, and therefore deep synoptic moisture is lacking. However,
there is abundant low level moisture. With dewpoints surging into
the low 50s over the 30F degree lakes, expect some advection fog to
develop overnight.  This is not a guarantee, but with the history of
the large scale fog formation upstream earlier together with Lake
Ontario fog this morning, would expect more widespread fog formation
tonight with the added moisture and warmth overhead.  Will issue a
dense fog advisory for the lake plains in anticipation of fog
development late today and/or tonight.  Otherwise, expect
temperatures to be w-a-y above normal, with lows barely dropping to
50F over WNY and into the 40s to the east.

In terms of precipitation...aside from the scattered showers moving
through the Southern Tier this afternoon, expect mostly dry weather
to last through tonight.  There may be some passing showers on
Thursday AM, but rainfall amounts should be negligible due to the
lacking moisture aloft.  Later Thursday afternoon, some semblance of
a lake breeze front may form toward the Southern Tier as the surface
low moves east across Southern Ontario.  The weak boundary together
with a weak trough south of the low may provide enough of a focus
for the development of a weak line of showers, but again, have a low
QPF in place.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/...
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.

&&

.LONG TERM /SUNDAY THROUGH TUESDAY/...
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 /19Z WEDNESDAY THROUGH MONDAY/...
The main concern for aviation will be the increasing potential for
IFR visibilities as a surge of warm and moist air spreads across the
region from the SW. Low ceilings will be more common inland. This
scenario will will be most apparent toward the end of the day with
some LIFR fog possible, and could last well beyond 12Z Thursday. The
relatively cold lakes will promote continued formation overnight.

Outlook...

Friday...morning Rain, but otherwise VFR. Saturday...Periods SHRA
with MVFR and local IFR, then windy.
Sunday...VFR but IFR to MVFR in lake effect snow SE of both lakes.
Monday...VFR, possible MVFR...depending on low location.

&&

.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 through Thursday.  A
weak front will move through Thursday evening.

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...Dense Fog Advisory from 7 PM this evening to 9 AM EST Thursday
     for NYZ001>005-010-011.
MARINE...None.

&&

$$

SYNOPSIS...ZAFF
NEAR TERM...ZAFF
SHORT TERM...TMA
LONG TERM...JJR
AVIATION...CHURCH/ZAFF
MARINE...CHURCH/ZAFF



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