Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 261814

Area Forecast Discussion
National Weather Service Buffalo NY
214 PM EDT Wed Jul 26 2017

High pressure centered over New England will drift off the East
Coast tonight. Showers and some thunderstorms out ahead of a slow
moving cold front may affect at least Western New York overnight
with additional showers thunderstorms possible on Thursday with
the frontal passage. Cool air and a drier airmass will settle
into the region on Friday for a mostly dry day. The exception
may be near the Pennsylvania border where showers will be
possible from a low passing further south into the Mid Atlantic
States. Another area of high pressure will then provide calm
dry weather this weekend.


Surface high pressure over New England this afternoon will drift
eastward, allowing for a cold front over the Upper Lakes to drop
SEward, over the Eastern Great Lakes region tomorrow.

We will remain dry the remainder of the afternoon courtesy of this
high pressure to our east. Visible satellite imagery displays low
clouds hanging tough over eastern zones, while mid and high level
clouds are thickening over WNY from upstream convection.

Dry conditions will remain through the evening hours, but we have to
watch for a few convective augmented shortwaves that may bring a few
showers or isolated thunderstorms to the region overnight. Greatest
chances will be along and east of Lake Ontario, ahead of the cold
front where low level moisture pooling ahead of the cold front, and
increasing theta-E aloft, coupled with several hundred J/KG of
MUCAPE may produce convective showers and thunderstorms. There will
also be chances for showers and isolated thunder south of Lake
Ontario where upstream convection over the UP of Michigan this
afternoon may reach our area overnight.

Tomorrow a weak cold front will drop across the region. Will go
with a slower timing of the front over the warmer lake
waters...and with surface high pressure still aways off over the
northern Plains and western Great Lakes. Chances for storms
through the morning hours will become greatest during the
afternoon...coinciding with the peak heating of the day (SBCAPE
values up to 2000 J/KG) and cold front passage. Bulk wind shear
will be weakening through the day, and severe threat at this
time will remain marginal across the region.

It will be a bit milder and becoming a bit more muggy tonight ahead
of the cold front than the previous night. Highs tomorrow will run
close to normal for the region.


Any left over showers Thursday evening will slowly dissipate across
the region as the airmass starts to dry up following the frontal
passage.  Surface winds will veer to the north/northeast with an
overnight low temperature in the mid 60s across Western New York and
upper 50s across the North Country. Mostly cloudy skies may prevail
toward Friday morning as the low level environment remains
relatively moist.

On Friday, an upper level trough over Saskatchewan will amplify as
it moves ESE across the Northern Plains and into the Upper Great
Lakes. At the surface, weak surface ridging will begin to slide
southeastward with a 1022mb high centered over Lake Superior.
Strengthening northeasterly winds with still relatively moist low
levels should promote a fair amount of upslope cloudiness across the
region. Given cool temperatures and strong northeasterly flow, high
resolution guidance has backed off on any afternoon convection
forming along lake-breeze boundaries.  Therefore, Friday should be
dry for most locations.  The one exception might be toward the
Southern Tier/PA border due to lift from the upper level low moving
toward the OH Valley.  Daytime highs should be cooler than Thursday
and generally end up in the low 70s.

Friday night...There will still be a low chance for showers in the
Southern Tier/PA border, as the latest models are still in
discrepancy with the placement of the low that will have moved into
the OH valley Friday evening. More than likely the low will be
located over the Ohio/Pennsylvania border. The overnight low
temperature should end up in the mid to upper 50s except for along
the lakeshore where temps may hover near 60.

By Saturday, strong 500mb ridging will slide from the Central Plains
into the northeast and over the region. At the surface, a 1022mb
high will move in and end up park right over the Great Lakes through
the entire weekend.  There may be some clouds toward the south from
the old low, now somewhere over the Mid Atlantic, but overall upper
level ridging and high pressure will push into the region providing
for a dry Saturday.  850mb temperatures are forecast to be near
+9/+10C.  This, combined with relatively strong northeasterly winds
picking up ample lake moisture off both of the lakes, should result
in at least some clouds early near Lake Ontario. Temperatures will
remain in the 60s with a daytime high in the upper 60 with
comfortable humidity levels.

Saturday night will have quiescent conditions with a low in the mid
50s under strong high pressure.  This pattern should provide ideal
conditions for river valley fog late Saturday night.


Picture perfect weekend weather remains on tap for all of
western NY and the North Country. Ridging builds into the region
Sunday with warming 850 mb temps back into the low teens C,
which will push our afternoon highs back to near normal with
highs around 80. Sunday will feature more abundant sunshine as
high pressure builds overhead.

Model solutions diverge for the start of next week with differences
in the magnitude of a trough over easter Canada. A stronger trough
may force a weak cold frontal passage through the area with some
scattered showers and a very subtle few degrees cooler in
temperature to near normal. A weaker trough would keep the stretch
of dry weather going from the weekend right into the early next week
with slightly above normal temperatures.


For the 18Z TAFS mainly VFR flight conditions are found across the
region...with spotty MVFR across the So. Tier in thinning low level
clouds, while more widespread MVFR/low end VFR strato-cu clouds are
found across eastern zones, including the KART airfield.

Tonight a cold front will stretch towards the region, with showers
ahead of the feature crossing near Lake Ontario and then points
eastward. While a few stray showers will be possible across KBUF and
KIAG, the more likely area will be east of lake Ontario and here
will place a -shra in the TAF for KART.

Tomorrow showers and thunderstorms will increase across the TAF
region ahead of a cold front. Activity does not appear to be much
more than scattered at this point, and will leave any mention of
convection out of the TAFS for now.


Thursday afternoon...MVFR/VFR with scattered showers and
Friday through Monday...Mainly VFR.


Departing surface high pressure will maintain minimal waves and
winds on the lakes and rivers through tonight. A cold front will
slowly pass across the waters tomorrow, with southwest winds
increase on the eastern end of Lake Ontario to 15 to 20 knots...and
waves building to around 4 foot.

Behind this front, winds and waves will increase some as cold
air on a northerly flow pours over the lakes. Winds will
increase, and though wave heights will fluctuate some, they
will near 5 feet along the southern shoreline of Lake Ontario
Thursday night through Friday night. Later Saturday and then
through the weekend high pressure over the Eastern Great Lakes
will bring fine boating conditions continuing through the
weekend as high pressure slowly passes by.





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