Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 251417

Area Forecast Discussion
National Weather Service Buffalo NY
1017 AM EDT Tue Oct 25 2016

Cold northwesterly flow will result in cloudy skies and below
average temperatures into Wednesday along with some scattered lake
effect rain showers. A low pressure system tracking out of the
Midwest is then expected to cross the lower Great Lakes Thursday,
bringing widespread rainfall. Another round of rainfall will be
possible this weekend, as another low pressure system drops across
the region.


An upper level low continues to spiral across Eastern Canada, with a
cold northwest flow across the Eastern Great Lakes region. This
flow, with 850 hPa temperatures around -8 to -10c, will continue
lake effect showers, with a few scattered synoptic showers falling
across the interior higher elevations this morning. With slight warm
air advection in the mid layers, drier air, and increased surface
ridging, combined with daytime heating this activity should wane
through the day. The column of air will be cool enough to allow for
a few graupel showers as well.

Skies will remain mostly cloudy today in the cyclonic flow aloft.
Any lingering northwest flow lake effect rain/wet snow showers will
come to an end tonight as high pressure centered over western
Ontario province ridges south across the eastern Great Lakes.

Temperatures will remain below normal today under weak cold to
neutral temperature advection. Highs will top out in the low to mid
40s wind steady northwest winds making it feel like temperatures are
only in the 30s. Tonight winds will slacken with increased ridging
promoting a better environment for radiational cooling. Lows will dip
below freezing for nearly everyone except the immediate lake shores
and beneath and lingering lake effect clouds.


Surface ridging will cross the region on Wednesday, leading to a dry
but cool day, as a chilly airmass will still be in place across the
area, courtesy of northerly low-level flow. A mixture of sun and
clouds during the first half of the day will give way to increasing
clouds across Western New York in the afternoon as a warm front
approaches the forecast area from the west-southwest. The chilly
start to the day, with most of the area starting out below freezing,
will be slow to warm into the low to mid 40s by the afternoon,
though the Tug will likely remain in the mid 30s.

Looking at Wednesday night, one of the most important factors will
be the temperature forecast. Temperatures across most of the
forecast area should only slowly fall out of their afternoon highs
as cloud cover increases with the northeastward progression of the
warm front. The lower elevations of Western New York will remain
warm enough for warm frontal precipitation that will be arriving
earlier in the evening to remain all rain. However, higher
elevations of the Southern Tier and Finger Lakes will like see snow
mixing in with the rain, as temperatures will be in the lower 30s,
with wet bulb zero readings likely hovering right around freezing
after the onset of precipitation. Likewise, as this warm frontal
band moves northeast towards the Eastern Lake Ontario region late
Wednesday night into Thursday morning, we may see at least a couple
of hours of snowfall, with accumulations of around an inch before
precipitation changes over to rain during the day on Thursday, as
temperatures climb into the mid to upper 40s. Across the highest
portions of the Tug, we may see 2 to 4 inches in some locations, as
temperatures here will experience the longest period of time near to
below freezing.

Precipitation will change over to rain across the board on Thursday,
as a compact, but potent, low pressure system tracks directly across
the lower Great Lakes. It is worth noting that southeasterly flow
ahead of this low will be well-placed to generate reasonably strong
downsloping winds off the Chautauqua Ridge along the Lake Erie
shoreline Wednesday night into early Thursday morning. A zone of
strong warm advection and isentropic uplift, coupled with strong
DPVA across the forecast area as the upper level trough supporting
the surface low approaches, will generate widespread rainfall on
Thursday, with many locations seeing upwards of an inch of rainfall.
This rain will give way to rain showers Thursday night, as the low
moves east of Lake Ontario and is supplanted by a secondary low that
develops along the Mid-Atlantic coast. Ongoing cold advection on
fairly uniform west-northwest in the wake of the low will likely
support lake-effect showers downwind of the lakes, with perhaps a
few snowflakes mixing in across the hilltops of the Southern Tier
and Tug Hill towards morning, when temperatures fall into the mid
30s. Lows in the upper 30s elsewhere should preclude any snowfall


Lake effect showers should taper off on Friday as surface ridging
and warm advection take hold across the region. This ridging will be
embedded within a highly progressive, low-amplitude, flow aloft. In
fact, there will little in the way of clearing associated with the
ridge as it rapidly crosses the area and the next warm front sets up
across the lower Great Lakes Friday night into Saturday.

Models differ with regards to the exact track and speed of the low
pressure system that will be aiding in the development of the warm
front across the area, but all guidance currently indicates that
Saturday should be another wet day across Western and North-Central
New York. Depending on the final track and speed of this low, Sunday
may end up being a wet day as well. After that, current indications
are that we should see a more prolonged period of dry weather next
week, as the longwave ridge currently over the Western U.S. shifts
to the eastern half of the country.

Regarding temperatures, the trend will be towards more mild weather
as we move into the weekend, with Friday`s highs in the 40s giving
way to 50s on Saturday, courtesy of the warm front. With the
northern tier of the country being inundated with mild Pacific air,
thanks to the low-amplitude flow regime described above, readings
will remain somewhat cool, but with little in the way of strong
swings in temperature, as highs will run close to 50 Sunday into
Monday, and lows in the upper 30s to mid 40s, and generally cloudy
conditions abounding. The arrival of the longwave ridge promises a
return to much milder temperatures by the middle of next week.


Persistent cold northwesterly flow across the Great Lakes will
continue to generate plenty of VFR cigs outside of lake effect this
morning. A few weak and narrow bands of lake effect rain showers and
possibly some patches of graupel/pellets are showing up across our
region on radar. Some wet snow may even perhaps fall across the
higher terrain of the Southern Tier east of KJHW. Cigs in lake
effect will run down to the MVFR level such as is occurring at KJHW
near 11z.

High pressure will expand across our region through today and
tonight bringing an end to the scattered weak lake effect. VFR will
be found outside of the lake effect through tonight.

Thursday...MVFR/IFR with rain showers likely.
Friday and Saturday...MVFR with a chance of lake effect showers.


Cold air advection in the northwesterly flow will keep a stiff
breeze in place on Lake Ontario today. Small craft advisories remain
in effect, as northwesterly winds 15 to 25 knots will keep
elevated waves along the south shore.

The brisk northwesterly flow is expected to persist into this
evening, at which point a broad surface ridge extending from a high
centered over James Bay progresses across the lower Great Lakes,
bringing another short-lived respite from small-craft advisory
conditions. Expect easterly flow to develop Wednesday and freshen
into Thursday, as another low pressure system tracks out of the
Midwest and across the lower Great Lakes.

High pressure will briefly ridge across the lake on Wednesday but
another fast moving storm system will arrive Wednesday night into


MARINE...Small Craft Advisory until 6 PM EDT this evening for



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