FXUS61 KBUF 190549

Area Forecast Discussion
National Weather Service Buffalo NY
149 AM EDT Fri Oct 19 2018

Surface high pressure will move from the Ohio Valley east across
Pennsylvania and off the Mid Atlantic coast by Friday. This will
allow a brief respite from the recent cool weather. However,
another shot of cold air will move in by Saturday along with more
showers. This will be followed by more lake effect rain and snow
showers southeast of the lakes Saturday night and early Sunday.


Temperatures will slowly rise overnight as warm air advection
continues across Western and North-Central NY.

An expansive area of high pressure currently over the Ohio Valley
will shift east to the Mid-Atlantic coast by late Friday morning.
Lake effect cloud cover should continue to decrease in coverage
tonight as increasing subsidence over the area will help lower
equilibrium levels over and downwind of the lakes. Increasing 850Ts
through the night tonight and warm air advection will also help with
lowering these heights.

Friday will start off with mostly sunny skies across much of the
area and warmer temperatures compared to what has been experienced
the past few days. With a southwesterly flow, temperatures across
the area should warm to the upper 50s to around 60 across Western
and North Central NY. The area will be on the northern fringe of an
area of high pressure that will shift off to the east. A
deamplifying mid and upper level ridge will shift east and give way
to increasing cloud coverage Friday afternoon into Friday night.

Cloud coverage will increase in advance of the next cold front that
will move through the area on Saturday morning. This approaching
cold front is associated with an area of low pressure that will move
across Northern Ontario and James Bay on Friday. As this area of low
pressure moves across Northern Ontario it will deepen and result in
a stronger pressure gradient between itself and the high pressure
shifting toward and off the Mid-Atlantic coast on Friday. With this
increasing pressure gradient the area will experience increasing
southwest winds for Friday into Friday night. Winds on Friday
will range from 15 to 25 MPH with gusts to around 35 MPH,
especially near the lake shores. With increasing vorticity
advection this area of low pressure is expected to continue to
strengthen as we get into the weekend.


Rain shower chances will increase Friday night and Saturday as a
cold front and associated mid level shortwave cross the area.
Precipitation should come in two waves, first with the cold front
late Friday night and into Saturday and then with the shortwave late
in the day Saturday. Although there will be measurable precipitation
at most locations, amounts should generally be light on the order of
a quarter inch or less. It will be warm enough for all rain showers
through Saturday afternoon. Expect high temperatures in the 50s
early in the day with falling temperatures behind the front. It will
also be breezy both ahead of and behind the front, with gusts of 30
to 40 mph.

An amplified upper-level trough will dig across the bulk of the
eastern U.S. Saturday night into Sunday behind the cold front and
will aid in bringing below normal temperatures as 850 mb reach -8C
by Sunday morning. Cold air streaming across the warmer Great Lakes
waters will bring support widespread northwest flow lake effect
showers. Model soundings keep low level vertical temperatures
profiles warm enough for mainly rain early Saturday night, before
profiles cool sufficiently for a mix and then change over to snow,
especially for higher elevations. This will perhaps lead to a minor
accumulation in any steadier or more persistent snow showers.

Lake effect showers will linger through Sunday afternoon before
starting to taper back late in the day. High temperatures on Sunday
will only be in the upper 30s to lower 40s.

Sunday night winds at the surface will back in response to a
shortwave tracking across the Northern Great Lakes. This will lift
any lingering lake effect activity northward (primarily off Lake
Ontario) Sunday night.


A shortwave and associated moisture diving across the Eastern Great
Lakes Monday will bring some enhancement to the lake effect
precipitation, mainly east of Lake Ontario where westerly flow over
the longer lake axis will bring greater chances for lake
development. P-Type will mainly be rain across lower
elevations...but on the Tug Hill a change to snow is possible,
especially early and late in the day.

Northwest flow behind the clipper low Tuesday will again set the
stage for lake effect off both Lakes. As lake induced equilibrium
levels rise through the day bands of showers/snow showers will be
possible to the south and southeast of the Lakes.

High pressure will nose towards our region Wednesday, bringing drier
air across the Eastern Great lakes Wednesday that will end lake
effect precipitation.

This area of high pressure will settle across the Eastern Great
Lakes Thursday, and likely bring a seasonably comfortable day with
sunshine and temperatures in the 50s.


VFR conditions are expected through Friday with surface high slowly
moving east across PA during this period. Lake effect clouds near
3000-5000' will move east this evening, but otherwise expect minimal
CIGS. Increasing high clouds will move in late Friday.


Friday Night...MVFR to VFR with showers.
Saturday...MVFR to VFR with rain showers likely.
Sunday...Mainly VFR but MVFR/IFR in lake effect rain and snow
showers southeast of Lakes Erie and Ontario.
Monday and Tuesday...VFR a chance of rain showers.


Southwest winds will continue on the lakes through Friday night.
Besides a brief lull in winds on Lake Ontario overnight, Small
Craft Advisory conditions will continue today. Southwest winds
will ramp up quickly after daybreak maintaining solid Small
Craft winds and waves on both lakes and the Upper Niagara River.
A cold front will approach the Lower Great Lakes tonight and
channeling across Lake Erie will lead to Gale winds. Winds
across western Lake Ontario will stay at high-end Small Craft
during this time.

Southwest winds will also lead to Small Craft conditions on the Saint
Lawrence River tonight.


MARINE...Small Craft Advisory until 6 AM EDT Saturday for LEZ020.
Small Craft Advisory until 6 PM EDT this evening for
Gale Warning from 6 PM this evening to 6 AM EDT Saturday
for LEZ040-041.
Small Craft Advisory until 6 AM EDT Saturday for
Small Craft Advisory from 6 PM this evening to 6 AM
EDT Saturday for SLZ022-024.



LONG TERM...Thomas
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