Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 180012
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
712 PM EST Tue Jan 17 2017

.SYNOPSIS...
A period of rain, with light freezing rain east of Lake Ontario will
push across the region into tonight, with showers of rain and
snow tapering off through the day Wednesday. It will remain mild
through the remainder of the week, with warmer air reaching the
region this weekend.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
Low pressure will track across Lake Ontario this evening. An area
of precipitation extends along an axis of mid-level warm air
advection which is across the North Country early this evening.
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 tonight,
with rain, freezing rain, and sleet all a possibility during the
evening hours. Elsewhere, temperatures are well above freezing
with just some lingering showers.

Winds will shift to the southwest behind the surface low. Winds
have already shifted across the Niagara Frontier, with this flow
advecting moist air (dew points in the mid 40s) into a cooler air
mass. This has resulted in areas of fog, which will spread into
much of Western New York this evening. This flow will also result
in some upsloping, with drizzle along with some lingering showers.
Temperatures will cool some behind the low, but should only fall
into the mid 30s in most areas overnight. The exception is the
North Country where temperatures should stay in the lower 30s
overnight with lingering concerns for freezing rain, or some snow
or sleet as thermal profiles cool.

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 /WEDNESDAY NIGHT 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 /00Z WEDNESDAY THROUGH SUNDAY/...
Low pressure will track near Lake Ontario this evening.
Southwesterly winds will advect moist air into the boundary layer
resulting in low cigs and fog. This will result in LIFR or lower
CIGs at BUF/IAG/JHW, 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.

There still should be plenty of moisture remaining trapped
beneath an inversion to result in widespread IFR-MVFR cigs which
will last most of the day Wednesday. 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...
Winds have diminished with the surface low moving across the lakes
this evening. Winds will shift to the southwest behind the
departing system this evening. There will be minimal cold air
behind this cold front, and conditions on Lakes Erie should remain
just below SCA tonight and into Wednesday...though waves and winds
may reach the lower thresholds of SCA on Lake Ontario Wednesday.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Winter Weather Advisory until 4 AM EST Wednesday for NYZ007-
     008.
MARINE...None.

&&

$$

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


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