Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 212043
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
443 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/...
Wednesday through Thursday a sharp mid level trough will very slowly
cross the eastern Great Lakes and New England. Cool temperatures
aloft, wrap around moisture, and increasing lake induced instability
will produce scattered showers and some lake effect rain showers
both Wednesday and Thursday. The lake effect rain will likely remain
disorganized most of the time, with the placement of the mid level
low overhead yielding moderate boundary layer shear and short fetch
northwest flow.

The lake effect rain showers will end by Friday as high pressure
briefly builds over the eastern Great Lakes. Model differences
become more significant by Saturday, with the GFS being faster than
the ECMWF with the next system. Given the model differences, have
just gone with a low chance of rain showers for next Saturday.

Temperatures will bottom out Wednesday and Thursday as 850mb temps
drop to around 0C. This will support highs in the 50s in most areas,
with higher terrain possibly staying in the upper 40s if enough
cloud cover persists. Temperatures will begin to warm by Friday and
Saturday as southwest flow increases ahead of the next system. This
warming trend will be temporary however.

Looking a little farther ahead, the overall pattern evolution over
the next two weeks will be for a steady turn towards cooler weather
as a longwave trough becomes established over central and eastern
North America. This pattern change will be in part driven by the
poleward movement of the remnants of Typhoon Lan in the western
Pacific by the middle of next week. The resulting influx of
latent/sensible heat and vorticity into the mid latitude westerlies
will strongly amplify the Pacific wavetrain, which in turn will
drive amplification downstream into North America. By the middle of
next week, a strong Aleutian Low will force a ridge to build over
the Gulf of Alaska, which will drift to the west coast of North
America by next weekend. This western ridge is forecast to last into
the first week of November, and aid in forcing a deep longwave
trough over central and eastern North America. This will bring more
fall like weather for the last week of October, and the possibility
of the first wintry weather during the first week of November. Stay
tuned.

&&

.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...HITCHCOCK
AVIATION...RSH
MARINE...RSH



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