Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 250612

Area Forecast Discussion
National Weather Service Buffalo NY
212 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.


Multiple narrow broken bands of marginal lake effect precipitation
continue to be picked up by radar early this morning in northwest
flow across the eastern Great Lakes. A capping inversion around
6-7 kft is keeping the lake bands weak and disorganized. Temperatures
this morning range from the mid 40s to upper 30s so lake effect
will mainly be rain showers but temps falling into the mid 30s
across the interior Southern Tier and Bristol Hills may finally
support some wet snowflakes, however little if any accumulation is

During the day Tuesday, drier air will build into the region,
combined with diurnal heating will help disrupt and break apart any
lingering lake effect.

Temperature-wise, the cold advection will be more noticeable
tonight, as readings fall into the 30s, with lower 30s across the
North County. Temperatures will remain crisp on Tuesday, with highs
only in the low to mid 40s.


Any lingering northwest flow lake effect rain/wet snow showers
will gradually come to an end Tuesday night as high pressure
centered over northern Ontario province ridges south across the
eastern Great Lakes. This high pressure will linger across the
eastern Great Lakes Wednesday supporting mainly fair, dry weather
with temperatures within a few degrees of normal.

Upper level energy off the West coast will track through the Rockies
and into Midwest by Wednesday night, with consolidating upper level
PV leading to cyclogenesis/deepening surface low, with the low then
tracking along or close to the southern Great Lakes. This will
develop widespread precipitation into the area from the west through
the night.

Using a general model consensus (Canadian/GFS/ECMWF), an initially
dry and cold airmass in place to start Wednesday night, thermal
profiles with the lead isentropic ascent/moisture advection closely
supporting the idea of a rain/snow mix east of the Genesee Valley
and all snow east of the Finger Lakes. Some wet snow accumulations
are expected across the higher terrain of the Finger Lakes and
North Country late Wednesday night/Thursday morning.

The low will continue to track east Thursday crossing just to the
north of the region continuing widespread shower activity. Strong
warm air advection pattern on a 50 knot low level jet will change
any snow to rain.

The system will then transfer its energy to a coastal low over the
Gulf of Maine by Thursday night. Wrap around moisture and continuing
cyclonic flow will keep chances of rain showers in play on the back
side of the system. Temperatures will run 10-15 degrees colder than
normal which may allow wet snow to mix with rain showers across the
Tug Hill region Thursday night.


A transitory low amplitude flow will be found across the country
during this period. While this type of pattern supports fairly
`regular` passages of Pacific based also lacks the
baroclinicity needed to support significant storms. Such will be the
case during this time one system will exit the forecast
area while the next will already be taking aim on the Lower Great
Lakes. In terms of to day fluctuations in advance
and in the lee of these systems will produce a roller coaster ride of
mercury readings...which by the end of the time frame will average
out to near normal levels. As for the day to day details...

A closed low spun up within a negatively tilted trough will drift
from eastern New York to the New England coast during the day
Friday. A moist cyclonic flow in its wake will keep showers over our
forecast least through the first half of the day...while
negative H85 temps will prevent temps from climbing out the 40s.

A shortwave ridge will quickly scoot across our region late Friday
and Friday evening...then the next system will already be on our
doorstep as day breaks on Saturday. Pending your model of choice...
rain showers to open the weekend will be provided by either the
passage of a cold front or by an organized sfc low that will slide
across our region along a pseudo warm frontal boundary. In either
scenario...rain showers will be likely for the bulk of our forecast

Scattered rain and wet snow showers will persist over our region
Saturday night into Sunday...but as in the case of Saturdays
event...there is low confidence as to the exact synoptic
environment that will be responsible.

All of the packages agree though that amplification of a broad ridge
over the nations mid section Sunday night will advance to the Ohio
Valley and Great Lakes region for Monday. This will favor a dry
start to the new work week.


Persistent cold northwesterly flow across the Great Lakes will
continue to generate plenty of VFR/MVFR cigs across the forecast
area this morning. A few weak lake effect rain showers are in place
across our region which will bring cigs down to the MVFR level such
as is occurring at KROC at 06z.

High pressure will expand across our region through today and
tonight bringing an end to the scattered weak lake effect mainly by
late this morning. 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 the lakes today. Small craft advisories remain in
effect, as northwesterly winds 15 to 25 knots will keep waves along
the south shores of the lakes.

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 9 AM EDT this morning for LEZ040-
         Small Craft Advisory until 6 PM EDT this evening for
         Small Craft Advisory until 9 AM EDT this morning for



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