Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 221416
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
1016 AM EDT Sun Oct 22 2017

.SYNOPSIS...
Another fine autumn day today with above normal temperatures, and
dry weather. Pleasant weather will start the work week...but will
quickly fade as a storm system bears down upon us late Monday and
into Tuesday. This system will bring a soaking rainfall and gusty
winds Monday night and Tuesday before ushering much cooler air with
some lake effect rain Wednesday and Thursday.

&&

.NEAR TERM /THROUGH TONIGHT/...
Visible satellite imagery showing abundant sunshine across the
region late this morning, with a few areas of high/thin cirrus
drifting east across the region.

High pressure along the eastern seaboard will maintain another dry
day, with sunshine and passing high/thin clouds from time to time.
850 hPa temperatures of 12 to 14C will bring another warm afternoon
with highs in the mid to upper 70s.

Tonight we`ll continue to see some clouds passing across the region,
that will again limit fog formation and maintain mild overnight lows
in the mid 50s to lower 60s.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
A mid/upper level trough will gradually dig across the Great Lakes
region through mid-week, resulting in a cooler and much wetter
pattern. Before this happens, 00Z model consensus provides just
enough ridging to keep most of the area dry during the daytime hours
on Monday. Showers may spread into far western New York late Monday
afternoon, with just increasing clouds elsewhere. Highs will again
be well above normal, ranging from around 70 across the interior to
the mid 70s across the lake plains where downsloping will help warm
things.

After this, there is no doubt it will rain with moist southerly 60-
70 kt 850mb flow developing and bringing a band of widespread
rainfall across the region. The progression of this LLJ will be slow
with minor model differences in timing, but in general this axis
will focus across Western New York Monday night and shift to central
New York and the Eastern Lake Ontario region on Tuesday. This will
bring a half an inch to an inch of rain to most areas. 1-2 inches is
possible across the Eastern Lake Ontario region, especially if a
second wave develops along the slow moving frontal boundary on
Tuesday.

In general, the strong flow aloft will remain aloft with breezy (but
not damaging) winds. The possible exception is downslope regions
such as the lake plains north of the Chautauqua Ridge and the Tug
Hill where stronger gusts may mix to the surface. Rain is likely to
arrive with the LLJ, and this can sometimes limit the mixing of
winds aloft. There is too much uncertainly to issue any wind
headlines at this time, but will add a mention to the HWO for
potential wind gusts in excess of 50 mph.

Otherwise a narrow dry slot should build behind the cold front across
far western New York Tuesday afternoon, with mainly dry weather and
even some breaks of sunshine. Temperatures on Tuesday will be
notably cooler, but still above normal. Highs will run from the
upper 50s to lower 60s across far western New York to the upper 60s
across the Eastern Lake Ontario region which will still be on the
warm side of the front during the morning hours.

By Tuesday night the front will be to our east with the upper level
trough axis across the eastern Great Lakes. Most model guidance
shows some semblance of a surface ridge axis extending into western
New York. Temperatures aloft will be cold enough (near 0C at 850mb)
for some lake effect rain showers, however a SSW surface flow would
focus most of this across Niagara county and into Canada. Otherwise
there is a small chance of a lingering shower with the upper level
trough.

&&

.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 /14Z SUNDAY THROUGH THURSDAY/...
For the 12Z TAFS VFR flight conditions are found with just some
high/thin passing cirrus clouds. These flight conditions are
expected to continue through tonight, with relatively light winds as
well.

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 will maintain light winds today and tonight, generally
15 knots or less.

A developing storm system will approach the eastern Great Lakes
Monday night and Tuesday. SE downslope winds over SW NYS will reach
the Lake Erie waters, with possible small craft advisories as early
as Monday evening. Winds will increase to possible small craft
advisory levels on Lake Ontario later through the night...with
additional periods of stronger winds and higher waves Tuesday and
into Tuesday night behind a cold front.

&&

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

&&

$$

SYNOPSIS...THOMAS
NEAR TERM...HITCHCOCK/THOMAS
SHORT TERM...APFFEL
LONG TERM...HITCHCOCK
AVIATION...HITCHCOCK/THOMAS
MARINE...THOMAS


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