Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 260555

Area Forecast Discussion
National Weather Service Buffalo NY
155 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.


Radar imagery shows scattered showers across the Eastern Lake
Ontario region early this morning. Most mesoscale guidance appears
overdone with this, so forecast uses extrapolated radar trends
rather than this guidance. These should exit to the east around 4
am, leaving the region dry by daybreak.

There is still lots of low level moisture with dew points around
70 across the region. A weak cold front forecast to drop across
the region overnight should squeeze this moisture, resulting in
fog or low clouds in many areas. Overnight lows should mainly be
in the upper 60s.

High pressure will ridge into the region today with lingering
clouds and fog dissipating by late morning. Temperatures will only
be a little bit cooler, with highs mainly in the lower 80s.
However, dew points will be notably lower by this afternoon with
these in the lower 60s which will make it feel much more
comfortable than yesterday.


Shortwave ridging building over the region will allow surface high
pressure to build over Western and North Central New York at the
beginning of the period. Larger-scale subsidence will keep the area
dry with mainly clear skies expected Friday night and mostly sunny
conditions for Saturday. The mostly clear skies will allow for
cooler temperatures Friday night with lows in the upper 50s to lower
60s, perhaps a few lower to mid 50s in the normally cooler locations
across the Southern Tier and east of Lake Ontario. Seasonal
temperatures in the upper 70 to mid 80s expected for Saturday.

A weak shortwave riding the periphery of the upper high centered
over the southern U.S. will lift up though Michigan into southern
Ontario Saturday night into Sunday. This should allow for an
increase in mid/high level cloudiness, with the latest model
forecast soundings keeping lower levels dry.

A warm front will lift through the eastern Great Lakes Sunday in
advance of a stronger upper trough working through the Upper Midwest
and western Great Lakes. This will bring the risk for a few
diurnally driven showers and thunderstorms for inland areas Sunday
afternoon. Sunday should be the hottest day of the period with 850
mb temperatures nearing +20C. This will translate into highs in the
upper 80s across the higher terrain to the lower 90s across the lake

By Sunday night the approaching upper trough, favorable right
entrance region forcing, and associated cold front working through
will expand the risk for convection across the entire area.


As we move into the new week, the aforementioned upper trough and
associated cold front cross the forecast area Monday. We will see
chances for showers and thunderstorms taper off from west to east
through the day 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 slight chance of showers forecast will
continue into Wednesday, as global models once again suggest
potential for showers, but for very different reasons, with the
ECMWF suggesting lingering showers along the slower cold front,
while the GFS is quicker to swing a warm front northwards towards
the area by midweek.

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.


The main concern for aviation is the potential for fog and
stratus to develop overnight. There is lots of low level moisture
in place, and this is likely to get squeezed as a weak cold front
slowly drops into the region. Expect stratus and fog to form first
across the climatologically favored Western Southern Tier with
IFR or lower conditions likely at JHW. Forecast confidence is a
bit lower elsewhere, but using a blend of HRRR guidance and
satellite trends a period of MVFR-IFR ground fog or low cigs is
probable at most sites. This should be with and just ahead of the
fropa which will be around daybreak.

Fog and stratus should dissipate relatively quickly today, giving
way to VFR conditions. After this there is high confidence in VFR
conditions this afternoon and evening as high pressure builds
into the region.

Expect valley fog to form Friday night, 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 Saturday.





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