Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 271853

Area Forecast Discussion
National Weather Service Buffalo NY
253 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.


A storm system shown by regional surface observations is found over
the eastern end of Lake Erie this afternoon. Visible satellite
imagery displays moisture expanding northward ahead of the low, while
northwest flow behind the low is bringing a wealth of low

Regional radars display a mix of rain and higher elevation snow
east of Lake Ontario, with various webcams displaying a minor
accumulation. Water Vapor imagery displays two shortwaves diving
towards the base of the upper level trough, with one shortwave near
Detroit, and a second shortwave over the northern portion of

For tonight the surface low will track along the Lake Ontario
shoreline to near the Saint Lawrence Valley. Widespread rain and
snow showers east of Lake Ontario will taper off to scattered
activity through the overnight period as this surface low
tracks towards the region. Here will also be the greatest likely
hood for subfreezing air temperatures tonight, with the potential
for any wet roads, or overpasses becoming slippery. The abundance of
clouds should limit the coverage area of slick spots though.

Plenty of moisture flowing behind the surface low will maintain
abundant clouds and scattered light rain showers through the evening.
Additional lift from the shortwaves, along with limited lake response
and upslope orographic lift will maintain chances for precipitation
through the overnight period. These shortwaves will also bring a
burst of cold air aloft, such that some of the rain showers will
end as a little light snow tonight across higher terrain, though
accumulations will be minor to none.

Tomorrow the initial surface low over the SLV will weaken, while a
secondary surface low develops near southern New England. While
precipitation will largely be ended over WNY, there may be a few
lingering areas of precipitation east of Lake Ontario through the
morning hours.

A narrow ridge of high pressure will advance towards the region
tomorrow afternoon. Once this ridge arrives we should see a rapid
decrease in cloud cover, with sunshine spreading eastward across
the CWA. Despite this sunshine, we will still remain chilly with
highs only in the mid to upper 40s.


The axis of the north-south surface ridge across the lower Great
Lakes will slide eastward Friday night. Southwesterly low level jet
increases to 45 to 55 knots by Saturday morning as shortwave energy
races across southern Canada, laying a sharp baroclinic zone across
the upper Midwest/Northern Great Lakes and Southern Ontario. The
increasing warm advection and moisture out ahead of this system will
bring increasing chances for showers to the North Country towards
Saturday morning, while the remainder of the region will remain dry.
The warm air advection and increasing southwest flow will result in
a non-diurnal temperature trend for most areas, with this most
pronounced across the lake plains of western New York where
overnight temperatures should warm into at least the lower to mid
50s by daybreak Saturday.

Saturday, latest models look to be just a tad bit slower with the
southward movement of the cold front. Nonetheless, it looks like the
boundary will ease through the area late in the day and Saturday
night. Increasing moisture and frontal lift will generate scattered
to numerous showers across the region, with the greatest rain
potential across the North Country. A breezy to windy day is
expected day as the pressure gradient tightens across our region in
advance of the cold front and as the 45 to 55 knot low level jet
translates eastward across the area. Momentum transfer scheme off
model soundings suggesting that we will not be able to tap into all
of this wind aloft with low levels rather stable, but still could be
looking at wind gusts in the 40 to 45 mph range, especially downwind
of the lakes. Likely not looking at much in the way of sunshine, but
still should be a rather mild late October day with most high
temperatures in the lower to mid 60s across western New York, with
rain holding the North Country back in the 50s.

The southward progression of the front will likely be slowed further
Saturday night into early Sunday as a wave of low pressure ripples
eastward along it. This will likely keep widespread showers across
the region Saturday night into at least Sunday morning. The greatest
rain potential across the western New York and the Finger Lakes.

The rainfall potential will diminish by Sunday afternoon as the
front drop south of the region. High pressure building into the
region behind the front will bring clearing skies Sunday night with
a good amount of sunshine expected for Monday. A gradually cooling
air mass will bring temperatures back closer to normal for Sunday
and Monday with most highs in the upper 40s to mid 50s.


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.


Will not make any changes to the small craft advisories that are in
place across the Eastern Great Lakes, except to add the Lower
Niagara River into a SCA for tonight through tomorrow morning. As
the surface low tracks from near eastern Lake Erie this afternoon,
to along the southern shoreline of Lake Ontario tonight a northerly
flow that may increase to 20 knots or so will necessitate a SCA

A narrow ridge of high pressure will cross the lakes tomorrow and
this will allow for SCA to end through the afternoon and overnight
time period on the lakes. However this will only be a lull, as
another storm system passing just to the north of Lake Ontario will
again freshen the winds on the Eastern Great Lakes that will likely
bring another round of SCA late Friday night and into the weekend on
the lakes.


MARINE...Small Craft Advisory until 2 PM EDT Friday for LEZ040-041.
         Small Craft Advisory from 6 PM this evening to 11 AM
         EDT Friday for LOZ030.
         Small Craft Advisory until 8 PM EDT Friday for LOZ043-044.
         Small Craft Advisory until 5 PM EDT Friday for LOZ042-045.



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