Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 212031
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
431 PM EDT Sat Oct 21 2017

.SYNOPSIS...
Beautiful indian summer weather will continue across the region
through at least late Monday afternoon...as high pressure along
the Mid Atlantic coast will supply us with conditions more typical
of late August or early September. A complex storm system will
then usher in a pronounced change in our weather...with a soaking
rain Monday night into Tuesday followed by much cooler temperatures
Wednesday and Thursday.

&&

.NEAR TERM /THROUGH SUNDAY/...
High pressure anchored off the Mid Atlantic coast will provide us
with a fine night across the region...as a deepening southerly flow
will help to hold our temperatures some 10 degrees higher than
those of early this morning. Mins will range from the upper 40s
across parts of the North Country and in the cooler Srn Tier valleys
to the mid 50s elsewhere.

Sunday will be an encore performance of Saturdays weather...as
sunshine through high clouds will combine with H85 temperatures in
the teens c to generate afternoon temperatures in the mid to upper
70s in most areas. Perfect weather for getting out to view some of
our picturesque Fall foliage.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/...
Pattern change set to take place during the period as the mid level
ridge shifts east and a deepening long wave trough settles across
the northern tier of states and into the Great Lakes. Latest
operational model solutions continue to trend toward a slower onset
of precipitation. The development of a cutoff low over the Gulf
coastal states will slow the eastward progression of the main upper
trough axis limiting the northward stream of gulf moisture until
very late Monday into Monday night. Will ramp up precipitation
probabilities starting late Monday afternoon in the west with
categorical by early Monday night, as negative tilted upper
trough swings moves into the Great lakes and surface low moves
into the Ohio valley. Due to the uncertainty of the interaction
with the cutoff low, confidence in the exact placement of the
heavier rain axis is low. Nonetheless, a rainfall event of an
inch or more is likely through Tuesday,

The longwave trough will settle into the Great Lakes/Ohio Valley
Tuesday/Tuesday night. Model solutions have trended deeper with this
feature. This will keep a chance/likely showers in the forecast
through this time period with the highest probabilities on Tuesday.

The delayed onset of precipitation Monday will allow for another well
above normal day with most temperatures reaching the upper 60s to
lower 70s. Coldest air is not set to arrive until after Tuesday, so
likely looking at temperatures Tuesday in the mid to upper 60s
across eastern sections, with upper 50s to lower 60s across the west.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
While the filling upper low will start to work its way across
the Lower Great Lakes on Wednesday...surface based ridging and a
lack of moisture in the mid levels will limit the extent of any
showers activity. The showers that we do develop should be most
prevalent over the far western counties where deeper moisture
will be available to interact with increasing lake instability.
The lake effect rain showers could become more widespread east
of BOTH lakes Wednesday night when the most unstable conditions
and sufficient synoptic moisture will be in place over the
lakes. It will also be much chillier...as H85 temps around zero
c will only support Wednesday afternoon temps that will range
from the lower 50s in the west to the mid to upper 50s east of
the Genesee Valley. While this will indeed by much cooler than
the preceding week...these temperatures will actually be close
to where we should be for late October.

Ridging is forecast to become established over the western counties
on Thursday...but the operational ECMWF is still suggesting that the
longwave trough will close off again...this time in the vcnty of
eastern Pennsylvania. This scenario could enable synoptic moisture
to back in across the eastern Lake Ontario for Thursday and Thursday
night before ridging finally takes hold of the entire region on
Friday.

&&

.AVIATION /21Z SATURDAY THROUGH THURSDAY/...
High pressure centered just to our south will provide ideal flying
conditions through the rest of this afternoon...as surface winds
under 10 knots will accompany generally cig free skies.

Tonight...VFR conditions will remain in place...although some valley
fog cannot be ruled out across the Srn Tier and Finger Lakes regions.

Sunday will be a carbon copy of Saturdays weather...as high pressure
along the Mid Atlantic coast will guarantee fine VFR conditions with
only some thick cirrus passing through.

Outlook...

Monday...VFR.
Monday night and Tuesday...MVFR/IFR with occasional rain.
Wednesday and Thursday...VFR/MVFR with a chance of showers.

&&

.MARINE...
High pressure along the Mid Atlantic coast will keep generally light
winds and negligible waves in place across the Lower Great Lakes
through the remainder of the weekend.

Winds and waves will remain well below small craft advisory levels
on Monday as a complex storm system will take shape over the Ohio
Valley. It will become quite unsettled Monday night into Tuesday
though...as notably stronger winds will accompany the passage
of the deepening storm system. Small craft advisories can be
expected from this event.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...None.

&&

$$

SYNOPSIS...JJR/RSH
NEAR TERM...RSH
SHORT TERM...TMA
LONG TERM...RSH
AVIATION...RSH
MARINE...RSH



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