Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 172308

Area Forecast Discussion
National Weather Service Buffalo NY
708 PM EDT Tue Apr 17 2018

An upper level trough will push slowly eastward with snow showers
tonight tapering off on Wednesday as this system exits into New
England. Another system will bring additional rain and wet snow
to the Eastern Great Lakes region Wednesday night and Thursday.


A broad upper level low will persist across the Northeast bringing
well below normal temperatures and snow showers. A robust shortwave
trough will exit into northeaster Pennsylvania this evening.
This, combined with the loss of diurnal heating will cause snow
showers to taper off during the evening hours. Even so, some
moderate snow showers are possible this time, briefly lowering
visibility to a half mile at times.

Meanwhile, there will continue to be a broad cyclonic flow
across the region. Another shortwave embedded in this flow will
move across Lake Ontario tonight, which will enhance snow
showers, especially east of Lake Ontario. Snow will ramp up
there late tonight and into Wednesday morning, mainly on the
Tug Hill Plateau. A Winter Weather Advisory is in effect for
tonight and Wednesday morning. Accumulations of 3 to 6 inches
are expected.

Winds will stay elevated 10 to 20 mph with gusts up to 30 mph
tonight. Low temperatures in the low 30s expected across low-lying
areas and upper 20s at higher elevations.

An upper level ridge will move into the southern Great Lakes
Wednesday morning behind the exiting upper level trough. With the
exception of some lingering snow showers across the Southern Tier,
mostly dry conditions are expected across Western NY Wednesday.
Temperatures will climb into the low to mid 40s, still well below
normal. Snow showers will linger longer east of Lake Ontario.


Wednesday night into Thursday a potent mid/upper level shortwave
will race eastward from the Midwest to New England...while merging
with and helping to re-amplify the larger-scale upper level trough
across eastern Canada and the northeastern states. Meanwhile at the attendant wave of low pressure over the Ohio Valley will
gradually deepen while sliding by just to our south across Pennsylvania
Wednesday night...then off the mid-Atlantic coastline on Thursday.
Deepening moisture and lift attendant to these features will result
in widespread light to moderate precipitation developing across the
area from southwest to northeast Wednesday night...then continuing
through the day Thursday.

At this point...both pattern recognition of a low passing by to our
south and current model thermal profiles suggest that the majority
of the precipitation from this system will fall in the form of wet
snow...with some rain mixed in at the onset Wednesday night...and
again during the day Thursday with diurnal warming of the boundary
layer and as the precipitation lightens up some. Total accumulations
for this 24 hour period look to be in the 1-2 inch range across the
lower elevations and 2-4 inches across the higher terrain...with
the greatest amounts likely focused across the higher terrain of
the Southern Tier...which will lie closest to the low track. While
such amounts currently lie under advisory is not out
of the question that some of the higher terrain of the Southern
Tier could ultimately reach lower-end advisory-type snowfall
amounts...a potential that will have to be watched over the next
day or so.

In the wake of this system...the lingering upper level trough and
a cold cyclonic northwesterly flow will help to produce some
additional snow showers and minor additional accumulations of an
inch or two Thursday night...with this activity then winding down
from west to east Friday and Friday evening as high pressure and
drier air build into the region...and returning diurnal influences
help to further disrupt these during the day Friday. After that...
fair and dry weather will then follow for the remainder of the
period as the aforementioned high builds directly across our

With respect to temperatures...daytime highs in the mid 30s to
lower 40s both Thursday and Friday will finally moderate some
into the lower to mid 40s on Saturday...however even then such
readings will still be some 10-15 degrees below seasonal normals.
Meanwhile...nighttime lows will mostly range from the mid 20s to
lower 30s.


Sprawling surface ridge over the Central Great Lakes will slowly
meander eastward and then overhead into early next week. Cool
conditions will persist with northerly cyclonic flow continuing on
the backside of the mid-level trough which will maintain below
normal high temperatures both Saturday and Sunday. A weak short wave
(Alberta Clipper)is forecast to drop southeast across Quebec Canada
and then into the Lower Great lakes late Saturday into Sunday. This
feature will help to maintain the mid-level trough and the cool but
dry northerly flow across the region through the weekend. Sunday
night, behind the passage of the latest short wave building 500mb
heights and the surface ridge moving overhead a significant warming
trend will initiate across the region Monday and then into Tuesday.

Expect a slow but gradual recovery of high temperatures over the
weekend. Saturday will be the coolest day of the period with highs
in the 40s. Sunday, expect L50s which for April is still below climo
(M/U 50s). Monday, highs will finally climb above normal with
temperatures expected in the U50s to near 60F and then L60s
everywhere Tuesday.


Snow showers will continue across the terminals into tonight.
Expect mainly MVFR conditions, with periods of IFR or lower
conditions in snow showers through tonight. Snow showers will
taper off on Wednesday, but MVFR cigs are expected to linger for
much of the day.


Wednesday night and Thursday...MVFR/IFR in rain...which may initially
be mixed with some wet snow across the North Country.
Friday...Mainly VFR with a chance of rain/snow showers.
Saturday...Mainly VFR.


A southwest wind will continue across the water bodies today,
generally in the 15 to 25 knot range. Small craft advisories will
continue for the lakes. As the upper level low and its
associated cool pool exits to the east tonight the winds will
begin to subside and waves begin to diminish Wednesday. Winds
are expected to remain strong a bit longer than the previous
forecast so some of these headlines were extended 3-6 hours for
the latest marine package.


NY...Winter Weather Advisory until 2 PM EDT Wednesday for
MARINE...Small Craft Advisory until 11 AM EDT Wednesday for LEZ040-041.
         Small Craft Advisory until 11 PM EDT this evening for
         Small Craft Advisory until 2 PM EDT Wednesday for
         Small Craft Advisory until 11 PM EDT Wednesday for LOZ044-



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