Special Marine Warning 63, NWS Buffalo, NY

Area Forecast Discussion
National Weather Service Buffalo NY
238 PM EDT Fri Sep 21 2018

.SYNOPSIS...
A deepening storm system passing from the upper Great Lakes to
Quebec through tonight will push a strong cold front across western
and north-central New York early this evening. It will remain quite
windy into this evening especially downwind of Lake Erie. A round of
strong to severe thunderstorms will develop along the passing cold
front. Fair, but much cooler weather can then be expected for the
weekend.

&&

.NEAR TERM /THROUGH SATURDAY/...
Cloudiness and the few showers earlier in the day have eroded this
afternoon, allowing for good mixing and considerable diurnal
heating. Strong gradient winds will continue into this evening,
especially downwind of Lake Erie where enhanced winds will be
channelled into the Niagara Falls and Buffalo areas with wind gusts
up to 50 mph possible.

Atmosphere gradually destabilizing this afternoon ahead of
approaching pre-frontal trough and surface cold front. Regional
radars showing broken lines of convection trying to develop upstream
ahead of these two features. Nearly all mesoscale guidance
suggesting this upstream activity will become much better organized
and will likely be sent through western and north central New York
as a convective squall line. This line of convection should be able
to maintain itself as it propagates into an area with surface based
CAPES nearing 2000 j/kg. Although the instability is not overly
impressive, our area will be within a strong sheared environment
with effective bulk shear strengthening to nearly 50 knots
suggesting strong/damaging winds will be likely with this line as it
pushes through the area between 5/6 PM and 9/10 PM.

Following the frontal passage late this evening, lingering rain
showers following the storms will quickly end from northwest to
southeast. The incoming airmass behind the cold front will be quite
cool, with 850mb temperatures falling to around +3C. This may
encourage a few scattered light lake effect rain showers early
Saturday morning south of Lake Ontario, but this will not amount to
much. Low temperatures will slip back into the 50s.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/...
Saturday night surface high pressure will be draped directly
across New York State...with attendant drying and subsidence
helping to scour out much of the lingering orographically-driven
stratocumulus across the Southern Tier. This will yield a return
to mainly clear conditions...which will combine with light winds
and our cool/dry airmass to produce near optimal conditions for
radiational cooling. This will result in overnight lows settling
into the 40s areawide...with the normally colder portions of the
Southern Tier and North Country possibly even dipping into the
chilly upper 30s. As has been pointed out in previous discussions...
Buffalo and Rochester have not seen sub-50 degree readings since
May 13th and June 26th respectively. The combination of the rather
cool temperatures and still-warm river waters will probably also
help promote the development of at least some valley fog across
the Southern Tier overnight.

Sunday and Sunday night a weak and moisture-starved cold frontal
boundary will wash out as it tries to push into our region from
Southern Ontario. This feature will therefore really just represent
a fading demarcation line between our pre-existing area of high
pressure and a second and stronger surface ridge building across
Northern Ontario and Quebec...while bringing little more than some
passing partial cloud cover to Lake Ontario and the North Country.
Otherwise dry and quiet weather will continue to prevail...with much
more plentiful sunshine and gradual modification of our airmass
allowing daytime highs to mostly recover into the mid to upper 60s
on Sunday. Following this...lows Sunday night will range from the
lower 40s across the North Country to around 50 across the lake
plains of far western New York.

Monday and Monday night the strong surface ridge will settle
southeastward from Quebec Province to the Canadian Maritimes...with
warm advection and an eventual influx of moisture/isentropic lift
consequently setting up across our region on a strengthening
southeasterly to southerly flow. As a result...initially dry weather
across our region for much of Monday should eventually give way to
slowly increasing shower chances by very late Monday afternoon/early
Monday evening across far southwestern New York...then across the
remainder of the area Monday night...when a warm frontal boundary will
also push into our region and provide a little more in the way of
synoptic-scale lift. This said...this still appears as if forcing
should remain weak/diffuse enough to keep any showers mainly scattered
in nature...for which a range of chance PoPs remains in play.
Otherwise...the steady warm air advection regime will result in
temperatures climbing back to slightly above normal levels...with
highs in the upper 60s to mid 70s Monday followed by lows primarily
ranging in the 55 to 60 range Monday night. The warmest overall
readings throughout this 24 hour period will lie across the lake
plains of far western New York...where an increasing southeasterly
to southerly downslope flow will be in place...and where the forecast
therefore aims a little bit above guidance temperatures to account
for this.

&&

.LONG TERM /TUESDAY THROUGH THURSDAY/...
On Tuesday the warm advection pattern will continue in between
strong high pressure over the western Atlantic and an elongated cold
frontal boundary slowly pushing eastward across the Upper Great
Lakes. While this will result in a continued opportunity for some
scattered showers...there could also be substantial rain free periods
as well...particularly in areas where a good southerly low level
flow leads to downsloping and attendant low level drying. With 850
mb temps pushing into the mid teens Celsius...daytime highs on
Tuesday should at least range from the lower 70s across the North
Country and interior portions of the Southern Tier to the mid to
upper 70s elsewhere given the southerly downslope flow...with warmer
readings than this certainly possible if sufficient breaks in the
cloud cover/shower activity materialize.

Tuesday night and Wednesday morning the aforementioned cold front
should slowly push eastward and across our region along with more
numerous showers...for which a period of high likely PoPs remains
in play. While instability looks to be rather limited due to the
unfavorable timing relative to the diurnal cycle...cannot rule out
a few isolated thunderstorms as well given the strength of the
front and its attendant swath of lift. Following the frontal
passage...the precipitation should then tend to steadily wind down
from west to east during the remainder of the day Wednesday...with
high pressure and cooler/drier air then bringing about a return to
fair dry weather for Wednesday night and Thursday. With respect to
temperatures...these should continue to average a bit above normal
through Wednesday...before settling back closer to late September
averages for Wednesday night and Thursday.

Looking further out toward the end of next week...the medium range
guidance is in loose agreement on another frontal system potentially
swinging another cold front across our region between Thursday night
and Friday...though much disagreement remains on the exact track
and strength of this system. With the latter and our distant vantage
point both firmly in mind...for now will just cover this with some
broadbrush lower-end chance PoPs...while also keeping temperatures
fairly close to seasonal normals.

&&

.AVIATION /19Z FRIDAY THROUGH WEDNESDAY/...
Skies have cleared across western and central New York this afternoon
resulting in widespread VFR conditions. Deep low pressure tracking
well north of the area creating a tight pressure gradient with
strong southwest wind gusts reaching 25-35 knots across much of the
area, with gusts to 40 to 45 knots possible at KBUF and KIAG through
about 00Z.

A line of gusty showers with embedded thunderstorms will sweep
across the eastern Great Lakes along a cold front late this
afternoon and evening with a risk for strong/damaging wind gusts.
All terminals could experience wind gusts of up to 50 knots as this
line of convection moves through between 21z-02z.

Tonight, winds will veer to westerly behind the cold front, but
remain gusty to about 20-25kts. Guidance indicates that MVFR low
clouds will develop overnight in the wave of the front.

Outlook...

Saturday...Cigs lifting to VFR.
Sunday and Monday...VFR.
Tuesday and Wednesday...Areas of MVFR with a chance of showers

&&

.MARINE...
A deepening storm system just south of James Bay will track well
north of Lake Ontario into Quebec through tonight. A tight gradient
will be maintained across the lower Great Lakes with sustained
southwest winds of 25 to 30 knots ahead of an approaching cold
front. Gusts could approach gale force through early this evening.
The combination of gusty winds and associated waves will continue to
create widespread Small Craft Advisories conditions into tonight.

Additionally, a line of strong to severe storms is expected to cross
the waters early this evening along the cold front. This line of
storms will likely create hazardous conditions on the lakes with the
potential for localized winds gusts exceeding 50 knots.

Winds will gradually slacken and waves will fall through Saturday in
the wake of the cold front. High pressure will build over the
eastern Great Lakes region through the weekend into Monday.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Beach Hazards Statement until 8 PM EDT this evening for NYZ001-
     007-010-085.
     Wind Advisory until 8 PM EDT this evening for NYZ001-002-010-
     011.
MARINE...Small Craft Advisory until 11 PM EDT this evening for LEZ020.
         Small Craft Advisory until 8 AM EDT Saturday for LEZ040-
         041.
         Small Craft Advisory until 11 PM EDT this evening for
         LOZ030.
         Small Craft Advisory until 2 PM EDT Saturday for
         LOZ042>044.
         Small Craft Advisory until 8 AM EDT Saturday for LOZ045.
         Small Craft Advisory until 11 PM EDT this evening for
         SLZ022-024.

&&

SYNOPSIS...TMA
NEAR TERM...TMA
SHORT TERM...JJR
LONG TERM...JJR
AVIATION...TMA
MARINE...TMA

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Special Weather Statement
National Weather Service Buffalo NY
259 PM EDT Fri Sep 21 2018

NYZ001-002-010>012-019>021-085-212130-
Niagara-Orleans-Northern Erie-Genesee-Wyoming-Chautauqua-
Cattaraugus-Allegany-Southern Erie-
Including the cities of Niagara Falls, Medina, Buffalo, Batavia,
Warsaw, Jamestown, Olean, Wellsville, Orchard Park,
and Springville
259 PM EDT Fri Sep 21 2018

...Strong Storms Expected Late this Afternoon and Evening...

A powerful cold front over southern Ontario this afternoon will
take aim on our region this evening. Showers and thunderstorms
will develop along and ahead of this front...with some of the
thunderstorms likely producing damaging wind gusts in excess of
60 mph.

The showers and thunderstorms will start to cross the far western
counties after 5:30 and should exit southern parts of Allegany
county around 8 PM. The highest risk for severe weather will be
found across the Southern Tier where an organized squall line of
damaging winds will be most likely.

Stay tuned to your favorite source of weather information for
possible watches and warnings.

RSH

Special Weather Statement
National Weather Service Buffalo NY
305 PM EDT Fri Sep 21 2018

NYZ003>005-013-014-212145-
Monroe-Wayne-Northern Cayuga-Livingston-Ontario-
Including the cities of Rochester, Newark, Fair Haven, Geneseo,
and Canandaigua
305 PM EDT Fri Sep 21 2018

...Strong Storms Expected Late this Afternoon and Evening...

A powerful cold front over southern Ontario this afternoon will
take aim on our region this evening. Showers and thunderstorms
will develop along and ahead of this front...with some of the
thunderstorms likely producing damaging wind gusts in excess of
60 mph.

The showers and thunderstorms will cross the Genesee Valley and
Finger Lakes regions between 6:30 and 8 PM. While the greatest
severe weather threat will be from damaging wind gusts in excess
of 60 mph...an isolated tornado cannot be ruled out.

Stay tuned to your favorite source of weather information for
possible watches and warnings.

RSH

Special Weather Statement
National Weather Service Buffalo NY
313 PM EDT Fri Sep 21 2018

NYZ006>008-212145-
Oswego-Jefferson-Lewis-
Including the cities of Oswego, Watertown, and Lowville
313 PM EDT Fri Sep 21 2018

...Strong Storms Expected Early this Evening...

A powerful cold front over southern Ontario this afternoon will
take aim on our region this evening. Showers and thunderstorms
will develop along and ahead of this front...with some of the
thunderstorms likely producing damaging wind gusts in excess of
60 mph.

The showers and thunderstorms will cross the Eastern Lake Ontario
region between 6:30 and 8:30 this evening. While the greatest
threat will be from an organized squall line generally south of
the Tug Hill...an isolated tornado cannot be ruled out for any
location.

Stay tuned to your favorite source of weather information for
possible watches and warnings.

RSH