658
FXUS61 KBUF 231125
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
625 AM EST Mon Dec 23 2024

.SYNOPSIS...
A relatively weak storm system over the Upper Great Lakes today will
track across Lake Ontario tonight. This will result in a general
widespread snowfall that will accumulate one to three inches tonight
into Tuesday over the western counties and as much as six inches
near the Tug Hill plateau. This should all but guarantee a white
Christmas for most areas. Dry uneventful weather will follow for
Christmas eve and Christmas Day. A notable warm up can be expected
late this week into early next week.

&&

.NEAR TERM /THROUGH TUESDAY/...
An area of Arctic high pressure will ease off the East coast
today...while a very robust shortwave will push a weak sfc low
across the Upper Great Lakes. Lift from an elevated warm front
extending east from sfc low could generate a brief period of very
light snow or flurries to the region during the midday...otherwise
we will have to wait until late this afternoon to start to
experience the effects of the next system. Any snow that does fall
during he daylight hours will be minimal and will cause NO TRAVEL
ISSUES. In fact...the pcpn may start off as a bit of a rain/snow mix
over and near Lake Erie.

The strong shortwave...defined as per the 1.5 PV sfc being folded to
as low as 600mb...and its associated weak sfc low will cross the
Lower Great Lakes tonight. Deep forcing from its passage will
support widespread snowfall that will accumulate 1 to 3 inches over
the western counties with as much as 6 inches of snow possible east
of Lake Ontario...and in particular over the southern slopes of the
Tug Hill. A winter weather advisory has thus been issued for the
Eastern Lake Ontario counties for tonight into Tuesday with the bulk
of the snow falling between midnight and daybreak. While the
vigorous shortwave will likely catalyze a short burst of snow that
could quickly cover area roadways...snowfall rates will otherwise be
under a half inch per hour. Travel problems should be minimal
outside of the winter weather advisory.

As the quick moving shortwave exits across New England on Tuesday...
high pressure centered over Quebec will arch back across all of the
Great Lakes region. With the forcing removed and all of the mid
level stripped away...residual light snow early Tuesday morning will
give way to nuisance lake enhanced/upslope snow showers that will be
focused over the Finger Lakes region. Additional snowfall on Tuesday
will be under a half inch in most areas. Unfortunately...the upslope
flow will maintain a wealth of strato-cu...especially south of Lake
Ontario.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH FRIDAY/...
Fairly benign weather overall through this period, however chances
look very good for most to have a white Christmas, especially
with the additional widespread light snow that will be laid down
by the system Monday night into Christmas Eve combined ground/
air temps remaining cold enough to hold onto the snowpack into
Christmas Day. Mainly dry weather expected to continue through
at least the end of the work week along with slowly moderating
temperatures. The details...

North-northeast boundary layer flow will gradually veer easterly
through Tuesday night as surface high pressure drifts a bit further
east into southern Quebec. Temps just marginally cold enough aloft
for any lake response, so any lingering nuisance lake enhanced snow
showers off Lake Ontario being directed southwest across western NY
will swing north eventually aligning with the long axis of the Lake
and aiming any lingering activity toward the Golden Horseshoe region
of Ontario Province on an easterly flow, although could still graze
areas along the southern Lake Ontario shoreline from around
Irondequoit/Sodus west. Otherwise, expect mainly dry weather as
aforementioned high pressure builds across the area from the north.
A typical early winter night temperaturewise with low ranging from
the teens east of Lake Ontario to the lower and mid 20s elsewhere.

Surface high pressure then looks to remain in control from Christmas
through at least the end of the work week. There is one mid level
shortwave that passes overhead later Wednesday night into the first
half of Thursday, however with the plethora of dry air in place,
expect conditions will remain mainly dry. Best chances for a stray
light snow shower look to be west and south of our area, further
removed from the center of the surface high. Otherwise, in the wake
of the shortwave, high confidence in mid and upper level ridge
really starting to build across the eastern third of the CONUS. This
will not only provide mainly dry weather toward the tail end of the
work week, it will also bring gradually warming temperatures through
Friday, possibly warmer than currently forecast just depending on
the evolution and location of said feature. Regarding temperatures,
highs ranging from the mid and upper 20s higher terrain to the low
30s on Christmas Day will slowly moderate to at least a range of 30s
by the end of the work week. Again, very possible temps Friday
overachieve current forecast highs.

&&

.LONG TERM /FRIDAY NIGHT THROUGH SUNDAY/...
High confidence in a substantial warmup during this period just
looking at the overall hemispheric pattern, however per usual it`s
the finer details that medium range guidance continues to struggle
with. In this case it pertains to how quickly the strong upper level
ridge is pushed east of our area, thus allowing a digging trough
across the upper Great Lakes to move east over our area, signaling a
return to more in the way of active weather. At this point, the
majority of deterministic and ensemble members keep dry weather
intact through at least a portion of Saturday before the longwave
pattern looks to make a more substantial eastward shift sometime
Saturday night or Sunday, with the ridge axis moving offshore as the
western trough further digs into the Great Lakes. As mentioned
above, this pattern will lead to a pronounced warming trend with
temperatures some 10-15 degrees above normal by this weekend
(possibly approaching 20 deg above average by Sunday). This will
translate to daytime highs well into 40s for most by Saturday with a
good shot at 50 or better by Sunday for the lake plains across
western NY.

Taking a closer look at sensible weather impacts, a series of
shortwaves embedded in the aforementioned trough to the west begin
to further encroach on the region this weekend. Chances for
precipitation increase as early as late Friday night through
Saturday as another warm frontal segment lifts into the area ahead
of the first of these waves, before a more potent southern stream
system possibly impacts the lower Great Lakes region during the
second half of the weekend bringing greater overall chances for
precipitation. Strong WAA pattern in place by this point should
support rain as the dominant p-type.

&&

.AVIATION /12Z MONDAY THROUGH FRIDAY/...
VFR conditions with light winds will be in place through at least
midday today. Warm advection ahead of the next system will then
encourage cigs to lower this afternoon with some light snow possibly
leading to MVFR vsbys by late in the day.

Conditions will significantly deteriorate tonight...as a weak storm
system crossing Lake Ontario will generate some widespread snow.
VSBYS will drop to IFR/LIFR levels with several hours of MVFR cigs
before cigs drop to IFR to LIFR levels after 06z.

Outlook...

Tuesday...IFR/MVFR in morning rain or snow showers, then VFR.
Wednesday through Friday...VFR.

&&

.MARINE...
Moderate southerlies will be found throughout most of the Lower
Great Lakes today...although winds will freshen enough over Lake
Erie to warrant small craft advisories. Otherwise...the southerly
flow will direct the highest wave action into Canadian or open
waters.

An area of low pressure will track across the region tonight with
winds veering to the west for all but the easternmost portions of
Lake Ontario. Without a change in wind speeds...this will maintain
SCA conditions on Lake Erie while a bit of a chop will be found
elsewhere.

As the area of low pressure exits across New England on Tuesday...
strong high pressure over Quebec will nose over the region. This
will prompt winds to continue to veer around to the north-northeast
with sub SCA conditions expected.

High pressure over the region Tuesday through much of the rest of
the week will result in only gentle to moderate breezes and
negligible wave action.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Winter Weather Advisory from 6 PM this evening to 1 PM EST
     Tuesday for NYZ005>008.
MARINE...Small Craft Advisory from noon today to 7 AM EST Tuesday for
         LEZ040-041.

&&

$$

SYNOPSIS...RSH
NEAR TERM...RSH
SHORT TERM...JM
LONG TERM...JM/PP
AVIATION...RSH
MARINE...RSH