Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 172303

Area Forecast Discussion
National Weather Service Buffalo NY
703 PM EDT Tue Oct 17 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 early this evening showing an area of high/thin
cirrus across the central Great Lakes and southern Ontario, which
will stream across the area through at least the first half of
tonight. A weak trough over southern Ontario may also bring a few
mid level clouds to the eastern Lake Ontario region from late
evening through the overnight. The overall trend will be for
mainly clear to partly cloudy skies overnight.

Large scale surface high pressure draped from the southern plains to
southern New England will shift just a bit further to the south
tonight. The gradient between this high and deep low pressure
exiting Quebec will maintain enough of a breeze to prevent much of
any fog development tonight. The southwest flow will keep overnight
temperatures milder than last night with lows in the lower 50s on
the lake plains and low to mid 40s in the cooler Southern Tier
valleys and Lewis County.

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.


A weak trough will move across northern NY and New England through
the first half of tonight, with just scattered mid level clouds east
of Lake Ontario and some high/thin cirrus elsewhere. VFR will
prevail overnight with the southwest breeze slowly diminishing. VFR
will continue through Wednesday. Any remaining thin cirrus will
slowly fade with SKC by afternoon.


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


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 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 Wednesday for LEZ040-041.
         Small Craft Advisory until 11 PM EDT this evening for
         Small Craft Advisory until 5 AM EDT Wednesday for
         Small Craft Advisory until 2 AM EDT Wednesday for LOZ042.
         Small Craft Advisory until 8 AM EDT Wednesday for LOZ044-



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