Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 180541

Area Forecast Discussion
National Weather Service Buffalo NY
141 AM EDT Wed Oct 18 2017

High pressure over the Ohio Valley will shift south tonight and
stall over the Mid-Atlantic coastline through the end of the week.
This will provide an extended period of dry weather and above normal
temperatures. The next chance of rain is forecast next Monday with a
cold front.


Satellite imagery this early morning displays lingering mid level
clouds across the North Country associated with a weak trough. These
clouds should largely be gone just past sunrise...with this region
joining the remainder of the CWA with clear skies.

Western and north-central New York will will remain between a strong
surface high pressure centered over the Mid-Atlantic and a
strong low progressing through central Canada on Wednesday. This
will maintain dry and warm, but breezy conditions. Winds will not be
as strong as today, but still expect gusts of around 20 mph
northeast of Lakes Erie and Ontario. Temperatures will climb to a
solid 10 degrees or so above normal with highs into the mid to upper
60s for most areas, and around 70 for the Genesee Valley into
Central NY.


Dry weather will continue from Wednesday night through Friday night
as the flow aloft only shows a weak shortwave moving across the
region on Thursday. This feature is an extension of a trough well to
the north near the Hudson Bay, and will feature a dry frontal
passage of little interest except for some transitory clouds and non-
consequential day to day temperature variability.  In short, expect
near or slight above normal high temperatures - mostly in the 60s
(or about 10F about normal).

Throughout this time, a surface ridge will be well displaced toward
the southeast US.  This will allow SW winds to prevail across the
lower Great Lakes region.  With the dry frontal passage, winds may
be gusty on Thursday, but probably not reaching advisory criteria.

Meanwhile, the above mentioned longwave trough will be embedded an
even larger longwave ridge over much of Eastern North America.  This
feature will begin to clearly show itself toward Friday eve as the
Pacific jet continues to force downstream amplification.  The short
term result will be the ridge over the Eastern US leading into the
weekend.  This ridge will ensure surface high pressure for Friday.


Strengthening Pacific flow in the mid levels will result in large
scale progressive amplification at 500mb with a trough in the west
and ridge in the east for the weekend. The trough will shift east
bringing weather more typical of fall toward next week but there
remains high model variability and low forecast confidence in
specific details. Despite this, an overall pattern change is
(finally) looking inevitable as we move deeper into Fall.

In the meantime, the ridge in place over the Midwest Friday will
slowly move toward the East Coast Saturday. Southwesterly flow on
the west side of the surface high will again pump warm air into the
region for Sunday. Both weekend days should remain dry  with
temperatures more typical of early September resulting in excellent
opportunities for outdoor activities.

The progressive amplified flow mentioned above means that the ridge
will soon be replaced with a trough.  Expect eventual surface low
development over Central Canada over the weekend with a cold front
probably arriving Sunday night or Monday with the GFS a bit
faster than the 12z EC.

As the mid level pattern continues to amplify, a deep, large upper
level trough will develop over the Great Lakes and eventually
Northeast US into next week.  The result will likely result in
numerous showers and cooler temperatures. Temperatures aloft do not
currently support snow, at least not through Tuesday. But, some form
of lake effect response is possible next week with 850mb forecast
to drop back below 0C.


VFR flight conditions for the 06Z TAFS will prevail through the TAF
period. Winds will generally be light, though a few SW gusts this
afternoon may reach 18-20 knots across the lake plain. Dry air
should prevent the formation of any widespread morning valley fog.


Thursday through Sunday...VFR except for local IFR in river valley
fog each late night and early morning.


Winds have diminished over the western end of Lake Ontario, and
the small craft advisory here will be dropped.

High pressure is in place, but expect fresh to strong breezes to
remain of the lower Great lakes into tonight as a tight pressure
graident continues over the eastern Great Lakes. Small Craft
Advisory conditions will be found for Lake Erie and portions of Ontario
through early Wednesday morning.

Another period of light winds/waves expected Wednesday as high
pressure shifts across the Mid-Atlantic region. The pressure
gradient over the eastern Great Lakes tightens up again Thursday
with the approach of a cold front, likely bringing another round of
Small Craft Advisory conditions.


MARINE...Small Craft Advisory until 8 AM EDT this morning for LEZ040-
         Small Craft Advisory until 8 AM EDT this morning for
         Small Craft Advisory until 5 AM EDT early this morning for



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