Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 261042

Area Forecast Discussion
National Weather Service Buffalo NY
642 AM EDT FRI AUG 26 2016

High pressure will build into the region today and Saturday with
a return to dry weather while temperatures remain above normal. A
weak cold front may produce a few showers and thunderstorms late
Sunday before high pressure returns for early next week.


A weak cold front will push southeast of the area and bring drier
and slightly cooler air into the region. Lingering clouds have
limited fog develop this morning, but there still is some patchy
fog across the Southern Tier valleys and Niagara Frontier which
will dissipate through about mid morning.

High pressure across the mid-western states will ridge into the
region this afternoon. Temperatures will only be a little bit
cooler than yesterday with highs mainly in the lower 80s.
However, dew points will be notably lower with these in the lower
60s which will make it feel much more comfortable than yesterday.

This high will be across the region tonight, providing mostly
clear skies and light winds. This will result in good radiational
cooling conditions which is likely to allow temperatures to drop
a bit cooler than consensus model guidance. Lows will range from
the mid 50s across the interior valleys to the lower 60s across
the lake plains. This also is likely to result in valley fog
across the Western Southern Tier.


Shortwave ridging building over the region will allow surface high
pressure to build over the region early in this period. Skies will
be mostly clear across the region early on Saturday, but increasing
high cloudiness is expected as a series of weak short waves/
vorticity maxima pass across the region ahead of a more pronounced
wave over Canada. Seasonal temperatures in the upper 70 to mid 80s
expected for Saturday.

The shortwave riding the periphery of the upper high centered
over the southern U.S. will pass though Michigan into southern
Ontario Saturday night into Sunday. This should allow for further
spread of the mid and high level cloudiness, and the latest model
forecast soundings keeping lower levels dry through Saturday night.

GFS and ECMWF are about 6 hours faster with the onset of
precipitation on Sunday than previous model runs. A strong surge of
high Theta-E air will arrive during the day on Sunday, accompanied by
a linearly stretched vorticity max during the peak heating of the
afternoon. Outside of lake breeze boundaries, there will be little to
drive surface convergence to initiate convection, but the right rear
quadrant of a 90kt 250mb will enhance broad scale vertical motion
over the Eastern Great Lakes and NY during the afternoon. A surface
trough will approach from the north during the evening and
convection should be pushed southward as well, exiting the region

Sunday should be quite a hot day with 850mb temperatures nearing
+20C. This will translate into highs in the upper 80s across the
higher terrain to the lower 90s across the lake plains. Even as the
surface trough crosses the region on Sunday night, there will be
little if any cooling associated with the trough, thus overnight
lows will not differ much from previous nights and remain in the
middle to upper 60s.


As we move into the new week, the cold front moves south of the
forecast area on Monday. There may still be a slight chance of
afternoon showers and thunderstorms, but this is a very low chance
as nominally cooler but considerably drier air filters in from Canada
and surface high pressure moves overhead.

After Monday night, a decent amount of uncertainty creeps into the
forecast, as the next shortwave upstream scrapes along the top of
the mid-level ridging parked over the Ohio Valley and Mid-Atlantic
states. Global models differ on the strength both of this ridging
and the shortwave and the associated surface cold front...but in
either case given the prevailing WNW flow across the Great Lakes,
this feature will not have a lot of moisture to work with and as
such will stick with just a slight chance of showers for Tuesday.
The front will push through the region on Tuesday night, with
chance of showers and lower chance of thunder.

Regarding temperatures, with the cool front moving through Sunday
night/Monday, we should see readings drop back closer to normal on
Monday, with highs in the lower 80s. However, with a generally flat
upper level pattern in place across the country and a jet stream
solidly confined to north of the border for the foreseeable future,
temperatures are likely to remain above average well into next week,
with highs in the low to mid 80s and lows in the low to mid 60s, or
around 5 degrees above average, through much of the week. There is,
however, a pattern change advertised by GFS and ECMWF with cooler
conditions possible for the end of the week...stay tuned.


Lingering clouds behind the front have limited fog development
across the region. Despite the lingering low level moisture, most
TAF sites are VFR early this morning. Any patchy fog should
dissipate quickly, however low clouds may fill into MVFR cigs.
This would be short-lived with high pressure building in, bringing
drier air and clearing skies this afternoon. This will bring VFR
conditions this afternoon and evening.

Expect valley fog to form tonight, which should mainly impact the
JHW terminal.


Saturday and Sunday...Mainly VFR.
Sunday night and Monday... Mainly VFR with a chance of showers
and thunderstorms.


High pressure will build across the region with fair weather and
fine boating conditions expected through the weekend. A weak cold
front may bring some showers or thunderstorms late Sunday.





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