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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KBUF 232010
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
410 PM EDT Thu Mar 23 2023

.SYNOPSIS...
Rain will end from northwest to southeast later this afternoon and
evening as a cold front moves southeast across the area. High
pressure will then build into Ontario and Quebec tonight through
Friday with a period of dry and cooler weather. Strong low pressure
will then move through the Great Lakes Saturday and Saturday night,
bringing another round of rain to the region. The rain may start as
snow or a wintry mix across the North Country. Strong winds are
possible Saturday night, especially across Western NY.

&&

.NEAR TERM /THROUGH FRIDAY/...
Radar imagery showing areas of light to moderate rain crossing the
region early this afternoon. A weak baroclinic wave running along an
advancing cold front is supporting the areas of steadier rain, but
both will quickly start to exit the area through the afternoon. The
most widespread rain will be through mid afternoon, with coverage
diminishing thereafter. The moist airmass over the cold lakes will
produce some patchy fog over Lake Erie and Lake Ontario, with some
of this moving into shoreline areas through the rest of the
afternoon and early evening. Lowering dewpoints will end this fog
potential by mid evening.

Rain will taper off from northwest to southeast from mid afternoon
through mid evening, with the last of the rain exiting the Southern
Tier before midnight as the cold front pushes quickly southeast of
the area. High pressure will build east across Ontario and western
Quebec overnight. There may be some initial clearing later this
evening, but as the airmass grows colder, expect post-frontal lake
effect and upslope clouds to expand with low stratus becoming
widespread overnight. Cold advection will drop temperatures back
into the upper 20s to lower 30s overnight.

Friday the frontal zone will stall well south of the area from the
Ohio Valley to the Mid Atlantic. High pressure moving east from
Ontario into Quebec will bring dry weather to the eastern Great
Lakes. Widespread lake effect and upslope stratus in the morning
will give way to some partial clearing by afternoon, especially on
the lake plains as stable lake shadows expand inland. A colder
airmass will keep highs in the upper 30s to lower 40s.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
This period will feature another round of active weather from later
Friday night into Sunday. This will come courtesy of a southern
stream trough initially over the mid-Mississippi Valley Friday
evening...which will deepen and eject northeastward to the central
Great Lakes during Saturday...before weakening some and sliding out
across Quebec and the Canadian Maritimes Saturday night and Sunday.
At the surface...this will spur an initial surface low to rapidly
deepen and follow along a similar path through Saturday...with the
system then becoming vertically stacked over the central Great Lakes
by later Saturday afternoon/Saturday evening. Increasing height
falls/DCVA along the front flank of the advancing mid/upper level
trough will then force the development of a secondary surface
cyclone along the New Jersey coastline Saturday evening...with
energy then transferring from the initial primary low to the
strengthening coastal system as it lifts northeastward off the New
England coastline to Nova Scotia through the rest of Saturday night
and Sunday.

This system will bring another round of widespread precipitation to
our area between later Friday night...Saturday...and Saturday
night...with liquid equivalent precipitation amounts through this
period expected to range from a half inch to an inch. With respect
to precipitation type...the track of the primary low will provide
for a substantial enough influx of warm air both at the surface and
aloft for the vast majority of the this to fall in the form of plain
rain. This said...thermal profiles continue to suggest the potential
for a brief wintry mix on the forward flank of this system...though
any snow/ice amounts look to be rather limited at this point due to
its expected short duration. The greatest potential for such will be
across the far eastern Finger Lakes and east of Lake Ontario where
thermal profiles will remain colder longer...and where up to a
couple inches of snow appear possible. Saturday night...colder air
wrapping in behind the primary system`s cold front will result in
the rain mixing with/changing back over to snow across the higher
terrain as it winds down...though any accumulations should again be
very minor.

Of greater concern with this system will be the potential for a
round of strong winds...especially across far western New York. The
initial primary surface low will wrap up rather quickly as it pushes
to the central Great Lakes on Saturday...with its central pressure
reaching the 980-985 mb range by later Saturday evening...and its
associated low level jet increasing to 55-65 knots as it overspreads
our region. Initially this will bring a threat of strong south-
southeasterly downslope winds during the day Saturday...with this
maximized along the Lake Erie shoreline downwind of the Chautauqua
Ridge. Following the passage of the surface cold front late
Saturday/Saturday evening...the threat will then shift to the
typical areas from the Lake Erie shoreline across the Niagara
Frontier to Rochester in the west-southwest cold advective
regime...which will help to more effectively mix down the higher
momentum air from aloft. In both cases model profiles continue to
suggest the potential for a period of higher-end advisory to lower-
end warning criteria gusts of 50-60 mph...and with this and
increasing confidence in this scenario in mind have opted to issue
some initial High Wind Watches as outlined below. Elsewhere more in
the way of lower-end advisory criteria gusts appear possible both
Saturday and Saturday night...and with the more marginal
conditions/lower confidence in these areas will opt to address these
later on as the event draws closer.

On Sunday the primary low will weaken considerably as it translates
eastward across Quebec and continues to transfer its energy to the
strengthening coastal system...with high pressure and drier air
nosing into our area during the afternoon. This will result in still-
rather windy conditions Sunday morning giving way to diminishing
winds Sunday afternoon...along with lingering scattered rain and
snow showers east of Lake Ontario steadily winding down. With good
mixing still in place coupled with the return of some partial
sunshine and 850 mb temps in the -2C to -7C range...Sunday`s highs
should range from the upper 30s to mid 40s east of Lake Ontario to
*at least* the mid 40s to lower 50s elsewhere...with the warmest
readings found across the Finger Lakes Region.

Finally...Sunday night should be mainly dry and quiet as the surface
ridge further builds across our region...with lows mainly ranging
from the mid 20s to lower 30s.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
-- Changed Discussion --
Heading into the new work week, subtle upper level ridging will be
in the midst of advancing eastward across the eastern Great Lakes.
Meanwhile a broad upper level low spanning across northern Canada,
will spread a trough southward across the north-central portions of
the continental United States. As the ridge pushes eastward, the
trough to the west will dig and dive into the upper Great Lakes
region, and then continue its eastward pass across the region
heading toward the East Coast by Tuesday night.

Translating the upper air pattern down to the surface, a surface
high over southern Ontario, Canada will be spread across the eastern
Great Lakes Monday. This will result in a period of dry weather.
Then due to cyclogenesis from the digging trough aloft, a surface
low will spawn over the Central Plains before passing east across
the Ohio Valley and then into the Atlantic. As of right now model
guidance packages differ with the timing of this system, and
therefore as a result have low chances for showers Monday night
through Tuesday night.

The model timing differences continue heading further into the
future of the forecast. Overall another upper level trough will dive
south across the Great Lakes and Mississippi Valley for later in the
week and results in another round of precipitation chances for the
end of the work week.

Additionally, conditions look to be on the cool side next week with
daily highs slightly below average and ranging in the low to mid 40s.
-- End Changed Discussion --

&&

.AVIATION /20Z THURSDAY THROUGH TUESDAY/...
A cold front will move southeast and exit the area later this
afternoon, with areas of rain tapering off from northwest to
southeast. Areas of IFR/MVFR CIGS will continue along and behind the
front through the rest of the afternoon before CIGS improve this
evening. Rain will produce areas of MVFR/IFR VSBY as well. The moist
airmass over the cold lakes will also produce patchy fog over Lake
Erie and Lake Ontario, and some of this will impact shoreline areas
at times through early this evening with local IFR.

Later tonight and Friday morning expect lake effect/upslope stratus
to expand, with areas of MVFR CIGS. The stratus will continue
through Friday morning before partial clearing by afternoon,
especially over and south/southeast of Lake Ontario where stable
lake shadows will help to clear out the clouds in the afternoon.

Outlook...

Saturday...MVFR/IFR with rain, possibly starting as a period of wet
snow or mixed precipitation across the North Country.
Sunday...Mainly VFR, through MVFR possible across the North
Country due to lingering mixed rain/snow showers.
Monday...Mainly VFR.
Tuesday...VFR/MVFR with a chance of rain/snow showers.

&&

.MARINE...
A cold front will move southeast and away from the lower Great Lakes
this afternoon and evening. Increasing northwest winds in the wake
of the cold front will bring a period of Small Craft conditions to
the eastern half of Lake Ontario from early this evening through
late tonight. High pressure will build east across Ontario and
Quebec late tonight and Friday, with diminishing winds.

Strong low pressure will then move from the Ohio Valley into lower
Michigan Saturday, then move across Lake Huron into Quebec Saturday
night through early Sunday. East to southeast winds will increase in
advance of this system, and may briefly approach gale force
Saturday. A longer period of southwest to west gale force winds are
more likely Saturday night through early Sunday following the
passage of the strong cold front.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
NY...High Wind Watch from Saturday afternoon through Sunday morning
     for NYZ001>003-010>012.
     High Wind Watch from late Friday night through Sunday morning
     for NYZ019-085.
MARINE...Gale Watch from Saturday afternoon through Sunday morning for
         LEZ040-041.
         Gale Watch from Saturday afternoon through Sunday
         afternoon for LOZ042-062.
         Small Craft Advisory until 5 AM EDT Friday for LOZ043-044.
         Gale Watch from Saturday evening through Sunday afternoon
         for LOZ043>045-063>065.
         Small Craft Advisory from 8 PM this evening to 5 AM EDT
         Friday for LOZ045.
-- End Changed Discussion --

&&

$$

SYNOPSIS...Hitchcock
NEAR TERM...Hitchcock
SHORT TERM...JJR/TMA
LONG TERM...EAJ
AVIATION...Hitchcock
MARINE...Hitchcock