Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 252034
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
334 PM EST Sat Feb 25 2017

.SYNOPSIS...
A strong cold front will exit to the east of the region this
evening, with falling temperatures and gusty winds behind the front.
Lake effect snow will bring minor accumulations east of Lakes Erie
and Ontario tonight into early Sunday before tapering off later in
the day. Temperatures will warm to well above normal again by the
middle of next week before winter cold returns by the end of the
week.

&&

.NEAR TERM /THROUGH SUNDAY/...
At 2 pm, a strong cold frontal boundary was along the eastern border
of the cwa exiting east of Lewis county. The heaviest rain and
widespread thunderstorms are along this boundary and also exiting to
the east. There is still steady rain with a few embedded
thunderstorms behind the front from Rochester to the east while it
is mainly dry west of Rochester. This will continue to move east,
following the progression of a sharp upper level trough.

Conditions will be much different behind this front with much cooler
temperatures and gusty winds. Late afternoon temperatures will
gradually fall from the lower 40s into the mid to upper 30s by this
evening. A wind advisory remains in effect for the lake plains of
Western New York. Consensus 12Z guidance has trended lower with
forecast 925mb winds with the GFS lower and now in line with the
NAM. This still supports low-end wind advisory gusts, with no
changes made to the headlines.

Tonight, the central pressure of the deepening surface low will
continue to fall below 980mb while shifting north across Quebec.
Strong cold air advection and wrap-around moisture will advect in
behind the systems cold front. The incoming cold air will change
post-frontal scattered rain showers over to snow showers along with
development of some modest lake effect snows east of Lakes Erie and
Ontario. 850mb temps will drop to around -14C supporting lake
induced equilibrium heights rising to around 8kft feet tonight into
Sunday afternoon. East of both lakes, the lake effect snow showers
will peak from late this evening into Sunday morning then taper off
Sunday afternoon first off Lake Erie as surface ridging builds
across the forecast area. Lake Ontario lake effect snow showers
could weakly persist into Sunday evening. Expect total amounts
through Sunday east of Lake Erie to run of 1-3 inches from the
Chautauqua Ridge east across the higher terrain. Totals east of Lake
Ontario will run 2-4 inches from tonight through Sunday mainly
across the Tug Hill and portions of Oswego County. In addition to
the lake snows, winds will remain quite gusty through Sunday as the
tail end of an 850mb jet lingers over the eastern Great Lakes. Gusts
in the 20s and 30s mph will be common. Low temperatures tonight will
dip down into the low to mid 20s tonight then rebound only into the
low to mid 30s Sunday.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/...
Sunday night a weak surface trough will move through southern
Ontario and Quebec, with a 50kt 850mb low-level jet crossing western
and central NY. While winds will run in the 10-20 knot range, point
soundings indicate a shallow inversion should keep any high gusts
from reaching the surface. A few snow showers cannot be ruled out
overnight east of Lake Ontario as the surface wave may force some
limited moisture up into the Tug and western Adirondacks.
Temperatures will likely not fluctuate too much with early overnight
temps in the upper 20s to low 30s warming to the low to mid 30s by
Monday morning.

Monday through Monday night, a general zonal mid level flow with
surface ridging and weak warm air advection will support mainly
cloudy skies with low to slight chances for some isolated showers or
sprinkles. Southwest flow will help temps rise into the 40s for most
on Monday then will dip down to the mid to upper 30s Monday night.

On Tuesday, low pressure will be developing over the Central Plains
with models showing an associated warm front and possible surface
wave shifting across our region. This will keep a chance for rain
showers Tuesday increasing to likely POPs across western NY Tuesday
night with warm air advection ahead of a strengthening low level jet
shifting into the Ohio Valley. Warm air ahead of this low will bring
back a midweek stretch of very mild temperatures with highs on
Tuesday running in the upper 40s to low 50s then only slipping back
into the low 40s across western NY and upper 30s east of Lake
Ontario Tuesday night.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
Very mild temperatures will remain for Wednesday ahead of the next
low pressure system and associated cold front. Abundant
moisture will continue to be drawn northward into the region
with precipitable water values nearing an inch, some 2 to 3
standard deviations above normal. This will bring a period of
widespread showers during the day Wednesday as the cold front
interacts with the mild and moisture laden airmass. Expect
temperatures once again to push into the upper 50s, and even the
60s for some on Wednesday.

Wednesday night into Thursday, a strong upper level disturbance will
push east over the area and pushing the surface cold front through
the area. This will bring a return to normal winter conditions by
end the week.

Upper trough digging into the Great Lakes will send 850 mb
temperatures down into the negative teens celsius later Thursday
through Friday. This will bring a threat for accumulating lake
effect snows, especially Thursday night through Friday night for
favored west-northwest flow areas. High pressure begins to
build into the area Saturday.

&&

.AVIATION /21Z SATURDAY THROUGH THURSDAY/...
The cold front has exited to the east of the area, with an
increasing W-SW flow expected through early evening. Expect mainly
VFR conditions this afternoon with the exception of ART where rain
showers will linger through mid to late afternoon with IFR/MVFR
conditions.

This evening lake effect snow showers will develop east of the
lakes. These may have a minor impact on BUF/ART...with a more
significant impact on JHW when the flow becomes more westerly.
Outside of lake effect, expect VFR conditions tonight.

Expect mainly VFR conditions on Sunday, with the exception of
lingering MVFR conditions due to lake effect snow showers at JHW.

Outlook...

Sunday night...VFR.
Monday...VFR, possible MVFR with chance of -SHRA/-SHSN.
Tuesday...VFR/MVFR with a chance of showers.
Wednesday...MVFR/IFR with showers likely.
Thursday...Mainly VFR. A chance of snow showers.

&&

.MARINE...
A strong cold front will sweep from west to east across the Lower
Great Lakes this morning and early afternoon. West winds will
increase in the wake of the cold front and peak during the late
afternoon on Lake Erie, and this evening on Lake Ontario. Both lakes
appear to peak just below gale force, with sustained winds reaching
30 knots for a few hours. This will bring high end Small Craft
Advisory conditions to both lakes. Stronger winds will continue
through Sunday night before the pressure gradient relaxes on Monday.

&&

.HYDROLOGY...
Multiple flood warnings remain in effect for the Eastern Lake
Ontario region. Thunderstorms moved across the area around noon,
with variable rainfall amounts, followed by a steady half inch
of moderate rain. Meanwhile, temperatures rose into the lower
60s as advertised resulting in rapid snow melt. NYS Mesonet
site webcams show this rapid snow melt.

The initial issue will be areal flooding, which is expected to
develop this afternoon and evening. The most vulnerable streams
and creeks will be those with source regions across the Tug Hill
and Adirondacks. There also may be flooding in many low-lying
areas.

It will take a bit longer for rivers to respond, but flooding is
expected at all 3 forecast points in the Black River basin.
Crests will occur first at McKeever and Boonville, with a much
later crest at Watertown. Expect an extended period of high
flows on the Black River from Lowville to Watertown. The
forecast only goes out through Tuesday, but Watertown may be
above flood stage for several days, with a crest expected on
Tuesday. Minor flooding is forecast for all 3 points, but it is
possible that Watertown and Boonville will approach moderate
flood stage. Flooding is also possible on non-forecast point
waterways such as the Beaver River and the Salmon River.

High flows will occur elsewhere, with some of the Buffalo Creeks
reaching action stage. With little if any snow pack left in
place, no river flooding is expected in any other basin besides
the Black River.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Flood Watch through Sunday evening for NYZ006>008.
     Wind Advisory until 10 PM EST this evening for NYZ001>003-
     010>012-019-085.
MARINE...Small Craft Advisory until 1 AM EST Sunday for LEZ020.
         Small Craft Advisory until 7 AM EST Monday for LEZ040-041.
         Small Craft Advisory until 1 AM EST Sunday for LOZ030.
         Small Craft Advisory until 1 PM EST Monday for LOZ043>045.
         Small Craft Advisory until 10 AM EST Monday for LOZ042.

&&

$$

SYNOPSIS...APFFEL/HITCHCOCK
NEAR TERM...APFFEL/SMITH
SHORT TERM...SMITH
LONG TERM...TMA
AVIATION...APFFEL
MARINE...APFFEL
HYDROLOGY...APFFEL



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