Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 180545
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
1245 AM EST Wed Jan 18 2017

.SYNOPSIS...
Low pressure will track across Lake Ontario and into the Saint
Lawrence Valley overnight through Wednesday. This will result in
some rain showers in most areas, with some mixed precipitation
across the North Country. It will remain mild through the
remainder of the week, with even warmer air reaching the region
this weekend.

&&

.NEAR TERM /THROUGH TODAY/...
Low pressure across Western Lake Ontario this evening will track
toward the Saint Lawrence Valley overnight. Steady precipitation
across the North Country will exit the region late this evening,
however there will still be showers and some drizzle lingering
behind the system overnight.

Based on the low track, winds should remain northeast in areas
located north of Watertown which should keep surface temperatures
near freezing for much of Lewis and northern portions of Jefferson
county. This will result in a mixed bag of precipitation
overnight, with a continued risk for freezing rain lasting much of
the night. Thermal profiles aloft will cool late tonight, with
precipitation trending toward rain or snow showers late.

Elsewhere surface temperatures will be warm enough for
precipitation to fall as all rain. The surface low will generate
some lift, followed by a shortwave later in the night. Mesoscale
guidance keys more on upslope precipitation, with areas of
drizzle possible between the showers. Winds have shifted to the
southwest across western portions of the cwa, advecting moist
boundary layer air which is interacting with the relatively cool
lake waters and then is getting trapped beneath an inversion. This
is resulting in areas of fog, which is best captured by HRRR
guidance. This fog will likely persist through much of the night,
then spread into the Eastern Lake Ontario region late tonight
before gradually diminishing Wednesday morning.

A passing upper level wave will interact with the low level moisture
to create a chance of rain in the morning, but conditions will
improve by the afternoon, even though skies will remain cloudy. High
temperatures on Wednesday will be in the middle to upper 30s.

&&

.SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/...
Where has winter gone? The blame can be placed on the shoulders of a
closed low anchored over Alaska and an anomalously strong tropical
ridge over the Hawaiian Islands whose combined efforts will direct a
very strong east Asian jet into the west coast of the country. This
pattern will continue to flood the majority of the continent with
Pacific modified air during this period...with temperatures over the
Lower Great Lakes region averaging some 15 deg F above normal mid
January standards. It is basically an extended version of a January
thaw.

Several robust shortwaves within the powerful zonal flow over the
Pacific will slam into the west coast during this period...and this
will lead to broad troughiness over the western half of the country
while downstream ridging will amplify over the Great Lakes and
eastern Canada. The warmth from such a pattern will be welcomed by
many...but the inevitable downside to this is will be a significant
rain event in the long term period. In the meantime...

General ridging will be found over the Lower Great Lakes Wednesday
night. While this will provide fair dry weather for the bulk of the
forecast area...the passage of a shortwave across the North Country
will be enough to warrant the maintaining low chc pops for that
region. In terms of p-type...H85 temps in the vcnty of -2 to -4c
will offer the chance for either rain or wet snow showers.

Fair dry weather can be expected Thursday and Thursday night...as
ridging will amplify over the Lower Great Lakes. This will be
accompanied by some weak warm advection with temperatures Thursday
afternoon climbing to within a few degrees of 40 over the western
counties. A little more cloudiness over the eastern Lake Ontario
region will likely keep that area in the 30s.

On Friday...the axis of a sharp negatively tilted ridge will extend
directly across our forecast area while a companion negatively
tilted trough will approach from the Upper Ohio Valley. Clouds will
advance across the far southwestern counties ahead of the weakening
trough...otherwise partly sunny skies will prevail with afternoon
temperatures climbing well into the 40s.

The anemic trough will continue to weaken as it will push northeast
across our forecast area Friday night and Saturday. Weak convergence
along this mid level boundary will be accompanied by a relatively
narrow band of moisture...so while there will be the low chc for a
bit of light rain (or ZR for parts of Finger Lakes/North Country)...
the vast majority of the time should be pcpn free. Temperatures will
fall back into the low to mid 30s Friday night before climbing back
into the mid 40s on Saturday.

&&

.LONG TERM /SUNDAY THROUGH TUESDAY/...
A progressive...yet highly amplified upper level pattern will be
found across the country during this period...with the Great Lakes
region being dominated by mild Pacific modified air. While this will
mean that temperatures will remain well above normal...the period
will be highlighted by what could be a soaking to problematic rain
on Monday into early Tuesday. More on this in a moment.

A ridge axis over eastern New York will support one more fairly nice
day across our forecast area on Sunday...although clouds will likely
prevail across the western counties. Temperatures will be some 15
deg F above normal values...with highs ranging from the upper 40s
across the far western counties to the lower 40s on the Tug Hill
plateau.

The fair weather will deteriorate Sunday night as a deep stacked low
over the Deep South will start to work its way up the western slopes
of the Appalachians. Ahead of this very dynamic system...a plume of
sub tropical moisture will stream northward from the Caribbean and
Gulf stream of the western Atlantic to Virginia and Pennsylvania. As
the leading edge of this moisture will make its way across our
western counties late Sunday night...it will be lifted by a strongly
divergent upper level flow. This will start the process whereby our
region could pick up a soaking rain.

On Monday...the vertically stacked storm system will slowly drift
north across the Upper Ohio Valley while the plume of sub tropical
moisture off the Atlantic will edge over our region. This will lead
to some widespread rain for our forecast area Monday and Monday
night. The highest risk for significant rains will be east of the
Finger Lakes.

Guidance continues to suggest that this storm system will also
support strong...potentially damaging...downslope winds between Lake
Erie and the Chautauqua Ridge. A southeast low level jet of 50-55
knots just above a staunch inversion is very similar to events that
local research has shown to be problematic. Stay tuned.

The slow moving storm system is forecast to cross Pennsylvania on
Tuesday while its plume of moisture will push across far eastern New
York into New England. Meanwhile..drier air in the mid levels will
advect across the western counties on Tuesday with dynamics
weakening considerably in the process. This will lead to a tapering
off of the rain from east to east.

&&

.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
Expect IFR/LIFR or lower CIGs at BUF/IAG/ART, with a potential
for a period of dense fog. This has the potential to lower vsby to
1/4SM at times in BUF/IAG, with increasing winds possibly
providing enough mixing to keep vsby in the 1/2SM - 1SM range.
Poor conditions should continue through at least midnight, with
gradually improving conditions likely late tonight as slightly
drier air moves in. Otherwise IFR conditions will prevail at
ROC/JHW overnight with mainly low CIGS.

There still should be plenty of moisture remaining trapped beneath
an inversion to result in widespread IFR cigs which will last most
of the day Wednesday. The one exception may be ROC where
southwestelry downslope winds may help improve to MVFR for the
afternoon. There will also be periods of showers and drizzle as
another weak disturbances crosses the area late tonight. Showers
will taper off from west to east Wednesday.

Outlook...

Wednesday night through Friday...Mainly VFR.
Friday night and Saturday...chance of rain and some MVFR/IFR.
Sunday...VFR.

&&

.MARINE...
Surface temperatures are not cold enough to enhance mixing,
but winds have picked up across Eastern Lake Erie early this
evening. This is the likely result of winds funnelling off the
Chautauqua Ridge. Because of this, have issued a brief SCA for
Lake Erie until WSW 925mb winds are progged to diminish early
Wednesday. Wednesday will be another close call, with winds/waves
expected to come close to SCA criteria on Lake Ontario. After
this, a modest southwesterly flow is expected persist through
Thursday with light winds Friday as high pressure ridges across
the waters.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Winter Weather Advisory until 4 AM EST early this morning for
     NYZ007-008.
MARINE...Small Craft Advisory until 7 AM EST this morning for LEZ040-
         041.

&&

$$

SYNOPSIS...APFFEL/WCH
NEAR TERM...APFFEL/WCH
SHORT TERM...RSH
LONG TERM...RSH
AVIATION...APFFEL/CHURCH
MARINE...APFFEL



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