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000
FXUS61 KBUF 170558
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
1258 AM EST Mon Feb 17 2020

.SYNOPSIS...
A cold front will slide across the Lower Great Lakes overnight with
just a few light snow showers and flurries expected. High pressure
will then push across our region Monday while bringing a period of
fair weather that will last through Monday evening. Low pressure
will then cross the Great Lakes later Monday night and Tuesday,
bringing warmer temperatures with an initial mix of snow and rain
changing to all rain, before colder air returns and leads to some
limited lake snows southeast of the lakes Wednesday and Thursday.

&&

.NEAR TERM /THROUGH TODAY/...
Early this morning a cold front lies across the eastern Lake
Ontario region and Lake Ontario...with scattered snow showers
upon it. As the front passes snow, and behind it, some brief
lake effect snow will develop. The p-type will merely be in the
form of some snow showers owing to renewed moisture within the
dendritic snow growth zone. Expect any accumulations to be under
an inch and mainly confined to areas east and southeast of Lake
Ontario...with the snow showers and flurries rapidly
diminishing late tonight and early Monday morning with the
departure of the front... and as the low level flow turns more
northerly and directional shear rapidly increases.

On Monday surface high pressure will build in rather quickly behind
the front, with lingering lake effect clouds and flurries south of
the lakes giving way to partly to mostly sunny skies in the
afternoon. Daytime highs will range from the upper 30s across the
western Southern Tier to the upper 20s across the North Country.

&&

.SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/...
Monday night, warm air advection will increase across the region,
and as a result, low temperatures will occur early and warm through
the night. This will result as southerly flow will increase as an
area of high pressure tracks to the east of the region and as a
developing area of low pressure tracks across the Great Lakes Monday
night into Tuesday morning. Early low temperatures will be in the
mid to upper 20s for most areas south of Lake Ontario, except for
some low 30s in the Western SOuthern Tier, and low to mid teens for
the North Country. The developing low will take shape and become
better organized on Monday evening over the upper Mississippi Valley
as a potent shortwave trough crosses the Northern Plains. POPs will
increase after Midnight Monday night as the area of low pressure and
cold front approach the area. Chance POPs will be in place a few
hours after Midnight across the far western portion of the area, and
continue to expand eastward through the early morning. Likely POPs
or higher will expand across most of the area by the time of the
morning commute. Most of the precipitation should be in the form of
rain as warm air advection continues ahead of the system, but snow
will be likely starting closer to daybreak east of Lake Ontario
where temperatures will be a bit slower to warm.

Tuesday, precipitation will be overspread across the entire area
after daybreak on Tuesday with snow for areas across the North
Country to start the day. Snow for areas of the higher terrain of
the North Country will accumulate to around 2 to 4 inches before
warm air advection changes most of the snow to rain. A few locations
in the highest terrain of the North Country may stay as a mix on
Tuesday and not change over to all rain. The best chance for
accumulating snow will be the southern portion of the Tug Hill where
upsloping southerly winds will enhance some of the snowfall. Higher
terrain of the Western Southern Tier may start as snow before
changing over to rain, with the potential for up to a slushy inch of
snowfall accumulation. A low level jet over the area late Monday
night into Tuesday morning will help enhance moisture transport and
warm air advection, resulting in the best chance for widespread
steady precipitation from around daybreak through around lunchtime.
The low level jet will also provide the area with some gusty winds
through the early afternoon. PWat values over the area will approach
eight tenths of an inch on Tuesday morning. Pwat values this high
are more normal for late in the Spring or early Fall. Steady
precipitation will taper off through the afternoon as the cold front
crosses the area. Cold air advection will start to cool
temperatures, but highs will reach the low to mid 40s for areas
south of Lake Ontario and the mid 30s to near 40 for the North
Country. Behind the cold front, showers that remain will start to
change back to a mix of rain/snow and eventually all snow as
temperatures cool.

Cold air advection will continue Tuesday night as another cold front
crosses the region, reinforcing the cold air advection, this will
cause 850H temperatures to drop to the -12C to -15C range by
Wednesday morning. With the cold air advection and some synoptic
moisture still available, a lake response will begin downwind of the
lakes. As of right now, snow looks like it should be light through
Tuesday night into early Wednesday morning before additional cold
air advection and an approaching trough for later Wednesday.
Temperatures on Tuesday night will be in the low to mid 20s, with a
few locations east of Lake Ontario in the teens.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
A broad upper level longwave trough will span eastward from the
Great Lakes to New England on Wednesday through Thursday. This will
allow for the colder temperatures to remain in the area for a couple
of days, with Thursday shaping up to be the coldest day. Along with
this pattern, general WNW flow combined with increased lake
instability shall produce a few rounds of lake effect snow showers
east and southeast of the lakes. While the model guidances are
hinting at a pattern conducive for lake effect snow, it is too early
to pin point the exact details. As it appears currently, this
pattern favors a better chance of producing accumulating snow for
the lake snows off of Lake Ontario rather than Lake Erie. The best
potential for these bands look to occur when there is a lake to lake
connection from Lake Huron into Lake Ontario on Wednesday night
through Thursday morning.

Lake effect snows southeast of the lakes will continue through
Thursday night, while diminishing during the morning hours on Friday
as warm air is advected into the region by an area of broad high
pressure. High pressure looks to remain overhead for the remainder
of the weekend, resulting in a gradual warming trend with dry
conditions.

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
A weak cold front will dip across Lake Ontario early this 06Z
TAF period, with just a few flurries of snow near KART and later
KROC. This front will bring MVFR ceiling heights to much of the
region by daybreak, and for the higher terrain of the Southern
Tier, IFR ceiling heights are likely around sunrise and a few
hours thereafter.

High pressure will then cross the region today, with light winds
and flight conditions returning to VFR.

Winds will become southerly tonight, and breezy as a 50 knot LLJ
develops overnight. With the boundary layer mixed, LLWS will be
spotty. While the southerly winds continue the second half of
tonight, a swath of precipitation (starting as snow across
eastern TAF sites) will push into the region from the Ohio
Valley with flight conditions deteriorating to MVFR (and IFR in
snow).

Outlook...

Tuesday...MVFR/brief IFR with mixed rain and snow changing to rain,
then ending. LLWS possible.
Wednesday and Thursday...Mainly VFR...except for localized MVFR/IFR
in limited lake snows southeast of the lakes.
Friday...VFR.

&&

.MARINE...
While winds across Lake Ontario are starting to diminish...Small
Craft Advisory-level waves will persist into the early overnight
hours across far eastern portions of the lake. Winds and waves will
then drop off further following the passage of a weak cold front
overnight...though some choppy conditions will still persist.
Behind the front high pressure will cross the Lower Great Lakes
on Monday.

Low pressure will then track across the central Great Lakes and
southern Ontario province Monday night and Tuesday. Southerly winds
will increase late Monday night and Tuesday, which may potentially
require additional Small Craft headlines.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...Small Craft Advisory until 1 AM EST early this morning for
         LOZ044-045.

&&

$$

SYNOPSIS...Apffel/JJR
NEAR TERM...Apffel/JJR
SHORT TERM...SW
LONG TERM...EAJ
AVIATION...Thomas
MARINE...Apffel/JJR