Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 271751

Area Forecast Discussion
National Weather Service Buffalo NY
151 PM EDT Thu Oct 27 2016

A storm system over the region this afternoon will track towards the
Saint Lawrence Valley with rain showers, and higher terrain wet snow
that will taper off through the overnight period, before coming
to a complete end east of Lake Ontario tomorrow midday. A ridge of
high pressure will bring brief amounts of sunshine tomorrow
afternoon, before clouds increase Friday afternoon and Friday
night ahead of the next storm system, one that will bring chances
for rain Friday night east of Lake Ontario, and Saturday across the
entire region.


Surface analysis this late morning places the center of a low over
central Lake Erie. Regional radars show a batch of precipitation
advancing across our region, with the back edge now near SW NYS, and
leading edge heading to areas east of Lake Ontario. Precipitation
has largely changed over to plain rain south of Lake Ontario, while
areas east of Lake Ontario, and in particular the Tug Hill remain
just cold enough to allow for some snow to fall. Accumulations will
be minor, just an additional inch or two, and again mainly on the
Tug Hill.

The bulk of the steady rain south of Lake Ontario will end through
the early afternoon hours, this as the low tracks towards the
southern shoreline of Lake Ontario. Continued wrap around moisture
behind the surface trough, and presence of the upper level trough
of low pressure will return rain showers across WNY through the
afternoon, especially on the upslope areas of higher terrain of SW
NYS. The moist lower levels will also contribute to low clouds and
patches of fog across higher terrain.

It will be quite breezy across much of the region today...with
strong winds possible through mid morning for the corridor between
Lake Erie and the Chautauqua ridge. For that particular area...
southeast downsloping winds could gust as high as 40 mph.

Temperatures today will exhibit a wide range across our forecast the mercury this afternoon will push into the mid to
upper 40s for sites within 15 miles or so of Lake Erie while readings
East of Lake Ontario within the steady pcpn will range from 35 to 40.

Tonight...a reinforcing shortwave will dive into the mid level
trough that had been supporting the weak storm system. This will
encourage the surface low over the Adirondacks to transition to the
New England coast with the occasional rain and lingering wet snow
over the North Country gradually tapering off to showers. Meanwhile
ridging over the Upper Great Lakes will approach our forecast area
from the west. This will establish a chilly northwest flow over our
region...with the resulting cold advection pushing H85 temps as low
as -5C.

While this will certainly be chilly enough to support instability
over the 15c lake surfaces...a strengthening subsidence cap under 8k
ft will severely limit the resulting lake response. Will only use chc
pops for the chilly west to northwest flow downwind of the lakes as
the synoptic pcpn gives way to the mesoscale.

Temperatures tonight will drop back into the 30s away from the
lakes...but all sites should remain above freezing.


By the start of Friday morning...the surface low responsible for
today`s rain and wet snow will be located over the North Country
and will be well into the process of transferring its energy to a
secondary low along the New England coastline...with this transfer
reaching completion Friday afternoon. Meanwhile...surface-based
ridging extending from the Ohio Valley to the Central Great Lakes
will build eastward through the day...with its axis reaching Central
New York by Friday evening.

For our region...all of this will result in lingering wraparound
precip across the North Country and spotty lake effect showers
southeast of Lake Ontario at the start of the day winding down
from west to east through early to mid afternoon...with increasing
drying/subsidence attendant to the burgeoning ridge also bringing a
return to at least some partial sunshine to areas south of Lake
Ontario. Otherwise...with a cool airmass still in will
be another day of below average temperatures with daytime highs
ranging from the lower to mid 40s across the North Country to the
mid and upper 40s across the rest of the area.

As we move into Friday night...the axis of the surface ridge will
quickly slide east into New the face of a pretty robust
northern stream shortwave and attendant surface low sliding eastward
across Central Ontario Province. Increasing warm advection and moisture
out ahead of this next system will bring increasing chances for some
scattered showers to the North Country overnight...while the remainder
of the region will be more likely to remain dry. The strengthening
warm air advection regime out ahead of this system will easily result
in a non-diurnal temperature trend for most areas...with this most
pronounced across the lake plains of far WNY where temps in the mid
to upper 40s Friday evening will climb into the lower to mid 50s by
daybreak Saturday.

On Saturday...the core of this system will slide east into northern
New England. In the process...this feature will push an initial
prefrontal trough across the area between the morning and early
afternoon hours...before slowly dragging its trailing cold front
into our region during the afternoon. Increasing moisture and lift
attendant to these features will generate scattered to numerous
showers across the region...with the greatest potential for these
found across the North Country. It will also be a breezy to windy
day as the pressure gradient tightens across our region in advance
of the cold front and as a 45-55 knot low level jet translates
eastward across the area...though with temperature profiles suggesting
that the low levels will remain fairly stable...would expect that
the strongest winds will remain confined aloft...with gusts in the
25-35 knot range a more likely outcome at the surface. With a much
warmer airmass in place...we can also expect a return to decidedly
above normal temperatures in spite of the increased cloud and shower
coverage...with highs ranging from the 55-60 range across the North
Country to the mid and upper 60s across areas south of Lake Ontario.

After that...the forecast picture becomes considerably more muddled
for the rest of the the individual members of the 00z
guidance suite continue to exhibit noteworthy differences in exactly
how far south the frontal boundary gets Saturday evening...before yet
another wave of low pressure ripples eastward along it later Saturday
night and Sunday. The various solutions currently range from the
Canadian GEM...which is most progressive with the front and confines
any showers to areas south of Interstate 90 by the time we reach Sunday...
to the NAM which is much slower with the fropa and would thus suggest
another round of fairly widespread showers for the latter half of the the next wave would be primed to pass directly across our
area. Meanwhile...the ECMWF and GFS lie between these two solutions...
with the former slightly more progressive with the front and somewhat
drier overall than the latter.

Given the various scenarios discussed above and the continued
difficulties the models have had in coming into agreement in handling
the front and this next this point feel it best to lean
more heavily toward a multi-model consensus for Saturday night and
Sunday. Using this as a guide...the slow-moving frontal boundary
should finish crossing our region Saturday night...before gradually
pushing further southward across Pennsylvania on Sunday as the next
wave of low pressure ripples eastward along it. This scenario would
result in at least a decent chance of showers lingering across our
entire area Saturday night and across areas south of Lake Ontario
Sunday...before coming to an end altogether by Sunday night as
expansive Canadian high pressure and drier air builds into our
region in the wake of this last system.

Temperature-wise...lingering cloud cover/precip/milder air should
lead to above normal temps continuing through Saturday night when
lows will likely be in the lower to mid 40s...before incoming cooler
air results in readings returning to slightly below average levels
for Sunday and Sunday night.


Unlike the short term period...this portion of the forecast
period still appears as if it will be dominated by broad upper-
level ridging that will build from the Mississippi Valley to the
eastern seaboard...and its corresponding areas of surface-based
ridging. These features will provide our region with a return to
warmer temperatures and largely dry weather...with the only
possible interruption to the latter coming on Tuesday when a weak
and rather moisture-starved cool front will cross the region...for
which only some broadbrush slight chance PoPs will be in play as
per continuity.

Speaking more specifically with respect to temperatures...
highs on Monday should range in the upper 40s and lower 50s...
before surging well into the 60s in many places on Tuesday
as significant warm air advection takes place in advance of
the aforementioned cool front. Following the passage of this
feature...readings will then pull back to the mid 50s to lower
60s for Wednesday...which while cooler will still be pretty
mild for early November.


A storm system tracking from near Lake Erie this afternoon to the
Saint Lawrence Valley tonight will bring widespread IFR and MVFR
flight conditions to the TAF sites. Expect the greatest period of
IFR flight conditions to develop this afternoon, behind the surface
low, with these poor conditions continuing through the bulk of the
overnight period. Flight conditions will begin to improve late
tonight and tomorrow morning, back to MVFR/VFR by the close of the
TAF cycle.

The heaviest rain/snow will occur within the first 6 hours of the
TAF cycle and mainly be east of Lake Ontario, while lighter activity
that will include some drizzle at times will pass across WNY through
the next 9 to 15 hours. As the low tracks eastward precipitation
will taper off later tonight. Winds, easterly ahead of the low will
rapidly shift to a west northwest flow behind the low, with
occasional gusts up to 25 knots.


Friday afternoon...VFR.
Saturday...VFR/MVFR with scattered to numerous showers developing.
Sunday...Mainly VFR with a chance of showers.
Monday and Tuesday...VFR.


Weak low pressure over northern Indiana will push to the east across
Lake Erie during the initial daylight hours today. The system will
then push east across Western New York during the afternoon before
making its way to the Adirondacks Thursday night.

This scenario will promote freshening southeasterly winds...which
will veer to the south and briefly weaken during the midday and
afternoon as the center of low passes over the Lower Great Lakes.
Winds will then freshen again in the wake of the system with fresh
to strong southwesterlies becoming westerlies late Thursday and
Thursday night.

This will sustain small craft advisory conditions over both lakes
through the period...with the easterly winds over the open waters of
Lake Ontario approaching gale force in advance of the system
for the first half of today.

High pressure over the Upper Great Lakes this evening will build
across the Lower Great Lakes on Friday...allowing winds and waves to
temporarily subside by late in the day. A storm system passing to
our north Friday night and Saturday will support freshening winds
again as we head into the weekend.


MARINE...Small Craft Advisory until 2 PM EDT Friday for LEZ040-041.
         Small Craft Advisory until 8 PM EDT Friday for LOZ043-
         Small Craft Advisory until 5 PM EDT Friday for LOZ042-045.



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