Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 230611

Area Forecast Discussion
National Weather Service Buffalo NY
211 AM EDT Wed Aug 23 2017

In the wake of a strong cold front...much cooler and drier air will
build across the region for the rest of the week. A few spotty
showers will remain possible Wednesday and Thursday...before high
pressure brings dry weather from Friday on through the upcoming


As of 2 am...regional surface analysis shows that the strong cold
front and any lingering showers have exited the area to the east...
with strong drying and subsidence in its wake already promoting a
return to mainly clear skies for the bulk of the for
our southeastern periphery where some leftover clouds still linger.
These will exit our region during the next hour or so...leaving
behind fair weather and mainly clear to partly cloudy skies for
the balance of the night. Expect overnight lows to settle into the
mid to upper 50s for the most part...with only the immediate
lakeshores seeing overnight lows around 60 degrees.

The axis of the deep upper level trough that has been driving the
unsettled weather across our region will be making its way into the
lower Great Lakes through the day on Wednesday. The combination of
diurnal instability being enhanced by falling heights aloft, lake
enhancement due to the increasing sfc-850mb delta-t on the lakes,
which will be increasing to +14C, and DPVA as a vorticity lobe
associated with the trough approaches the region may result in the
development of increased clouds and scattered showers in the
afternoon. The fly in the ointment however will be a lack of deep
synoptic moisture. As such, while it should be more cloudy than
sunny in the afternoon, the actual chance of showers will remain
relatively low, around 30 percent. Temperature-wise, the effects of
the cold frontal passage will be quite noticeable, producing a much
more comfortable day across the area, with highs in the low 70s, and
substantially less humidity, as dewpoints will fall into the low 50s.


The main feature of note during this period will be an upper level
trough that will be in place across the northeastern U.S. through
the period. A pair of shortwaves dropping out of Canada will
reinforce the troughing across the region, and with 850mb temps
falling to +6C generating a robust lake response, we can expect
fairly widespread cloud cover at least through Thursday. Shower
chances south/southeast of the lakes will only run to about 30
percent at best though, as there will be a dearth of moisture aloft.
It start to feel fall-like temperature-wise, with the trough causing
temperatures to fall into the upper 40s to mid 50s both Wednesday
night and Thursday night, with highs only reaching the upper 60s

Expect sunnier skies to end the work week on Friday, as the latest
shortwave passes to the east and surface high pressure begins to
build in from the upper Great Lakes. The corresponding
subsidence and very dry airmass, along with light winds aloft,
should outweigh lingering lake instability to provide for a
brighter end to the week, though it will remain on the cool
side, with highs in the upper 60s.


A pleasant weather pattern is expected over the weekend and heading
into next week. Model consensus (ECMWF/GGEM/GFS) builds surface high
pressure across the region throughout the entire long term period.
This will result in a prolonged stretch of dry weather, with partly
to mostly clear skies. The back edge of an upper level trough will
pivot across the region Saturday night and Sunday. With 850 mb
temperatures falling to around +6C there may be some lake effect
clouds, and the shortwave may spark a stray shower.  This said, the
dry air mass will limit the potential for anything more than widely
scattered showers. Otherwise, the cool air mass will result in cool,
almost fall-like temperatures. Over the weekend highs will average
in the lower 70s with overnight lows falling well into the 40s
across the interior valleys. Temperatures will warm slightly early
next week, with highs in in the lower to mid 70s.


As of 06z...the strong cold front and its associated shower activity
have cleared the area. Strong subsidence and drying in its wake have
already brought clearing to a majority of the area...with only some
leftover VFR cloudiness found along our southeastern periphery. This
will exit our region by 07z...leaving behind dry VFR weather for the
balance of the night.

On Wednesday VFR conditions will continue to prevail...albeit with
an increase in cumulus/stratocu with diurnal heating of our much
cooler airmass. During the afternoon...some spotty light showers
will become possible as an upper level trough axis/associated weak
secondary cold front pushes into our region...however these are
unlikely to have any impact on aviation operations.

Any scattered light showers from Wednesday afternoon will then tend
to die out with the loss of heating this evening...leaving behind
mainly dry weather until some scattered light lake effect showers
potentially develop late along and a little inland from the south
shore of Lake Ontario. Otherwise flight conditions will remain
predominantly VFR...with some spotty MVFR possible late along and
a little inland from the lakeshores.

Thursday...VFR/MVFR with a chance of showers.
Friday through Sunday...VFR.


As of 2 am...winds and waves on Lake Erie have fallen below advisory
levels...which allowed for the cancellation of the Small Craft Advisory
with the last forecast update.

Westerly winds in the wake of a cold front will have a long enough
fetch on Lake Ontario to keep waves in the 4 to 7 foot range on the
eastern half of the lake through the day on Wednesday, warranting a
continuation of SCA headlines into Wednesday evening, at which point
winds should diminish as the low pressure system responsible for the
winds pulls away from the region and high pressure begins to build
in from the upper Great Lakes. Thereafter, fairly tranquil
conditions, with waves 2 feet or less, will be found on the lakes
through the rest of the work-week, as high pressure slides across
the region.


Westerly winds will freshen in the wake of a cold frontal
passage tonight and will remain strong through Wednesday. The
increase in winds and wave action will bring and increase in
shoreline erosion and lakeshore flooding to the east half of
Lake Ontario when combined with the already high lake levels.
The static lake levels have dropped since late spring and early
summer, so the impacts of this event are not likely to be as
significant as earlier in the season, but still enough to
warrant a Lakeshore Flood Warning.


NY...Lakeshore Flood Warning until 11 PM EDT this evening for
     Beach Hazards Statement from 6 AM EDT this morning through
     this evening for NYZ003.
     Beach Hazards Statement from 6 AM EDT this morning through
     this afternoon for NYZ002.
MARINE...Small Craft Advisory until 6 AM EDT Thursday for LOZ042>045.



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