Rochester, New York 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

357
FXUS61 KBUF 211501
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
1001 AM EST Thu Nov 21 2024

.SYNOPSIS...
A complex area of low pressure will move across the region today
through Saturday, producing periods of cold rain and wet snow.
Lower elevations will see little or no accumulation, but higher
terrain will see minor to moderate slushy accumulations this
evening through Friday. Somewhat drier weather will return
Sunday as high pressure builds into the area.

&&

.NEAR TERM /THROUGH FRIDAY/...
A strong cold occlusion extending south of a strengthening surface
low over the upper Great Lakes exiting the eastern portions of the
forecast area will continue into the eastern Adirondacks this
morning. Steady rain focused along this boundary pushing through the
North Country, with a sharp dry slot working in behind the boundary
across western New York. Colder air wrapping into the region
generating a lake response off Lake Erie as 850 mb temperatures fall
to near -4C. This activity has developed into an organized band and
is located along  the northern edge of Lake Erie across Grand Island
and into Niagara County.

The surface low over the upper Great Lakes will drop south into
the Ohio Valley through the day today. As this occurs, a
secondary low will develop near the New York/New Jersey
coastline. This will send abundant moisture westward into the
region supporting the westward expansion of synoptic rains
through the day today. Some wet snow may mix in at times across
higher terrain, but any accumulation will be minimal through
the daylight hours.

Winter Weather Advisories have been issued for the Wyoming Hills and
higher terrain of the western Southern Tier Tonight through Friday
morning.

Complex elevation snow event shaping up tonight into Friday. This
is certainly a challenging forecast aw the coastal low will
continue to deepen as it takes an unusual westward track across
the region. Thermal profiles during this event will be changing
with time as colder air initially in place will eventually be
replaced by a warming profile as milder air from the east gets
pulled into the system. Moisture will be plentiful as moisture
gets advected from the Atlantic, supporting a large precipitation
shield. Lower elevations will stay all rain for the most part
with some wet snow possible earlier tonight (little if any
accumulation is expected), and if precipitation rates are high
enough a slushy coating to an inch is certainly possible. Colder
air, which will be more supportive of wet snow, will be found
across higher terrain (above 1500`) where surface temperatures
will be in the lower 30s. The expected deepening of the westward
moving surface low should allow for a favorable setup for
mesoscale forcing as the producing bands of heavier enhanced
precipitation from the Finger Lakes region into the Southern
Tier of New York. Snowfall amounts will likely be in the 2-7
inch range at elevations above 1500`. The snowfall range is set
a bit larger due to the complex nature of the surface low track
and thermal profiles.

Drier air will enter the eastern Lake Ontario region late tonight
into Friday, but a few inches of snow will certainly be possible on
the Tug Hill region.

The surface low will move southward into eastern Pennsylvania
Friday. Dry air will move into the forecast area and precipitation
will dwindle down from east to west. Surface temperatures will
slowly rise Friday and precipitation will change to rain. Rain will
likely persist across far western NY through Friday.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
The center of the anomalously deep upper level low will translate
eastward across the Long Island coast Friday night before making a
northeast turn towards the Gulf of Maine. A N-S oriented ribbon of
Atlantic based moisture will become sandwiched between a wedge of
dry air circulating around the eastern periphery of the low and a
mid-level ridge moving into the central Great Lakes. The axis of
this deeper moisture will lie in the vicinity of central Lake Erie,
which will maintain a likelihood for precip across far western NY
with only low-end chances for showers further east. Low level temp
profiles will again support plain rain as the ptype in most areas,
while the interior Southern Tier and Tug Hill/Western Dacks will be
cold enough in the upper 20s to support all or mostly wet snow.
There could be some nuisance accumulations (under 1") across these
areas through daybreak Saturday.

As the low begins to move further northeast off the coast later
Friday night into Saturday it will pull the Atlantic moisture back
eastward across the forecast area. Cool WNW flow (850H temps still
around -2C) with this increase in moisture will lead to a
reinvigorated lake response, causing showers to expand across much
of the area through the day. The main lake enhanced/upslope areas
east and southeast of the lakes will see the most activity through
the day, though the warmer daytime temps will support rain as the
dominant ptype even at higher elevations. Temps cooling overnight
Sunday night will be marginal in supporting any additional wet snow
across the higher terrain areas.

Overall shower activity should begin diminishing in coverage late
Saturday night as the moisture associated with the stacked low, now
over New Brunswick, continues to pull away. The primary lake effect
areas will struggle to dry out however, as a mid-level shortwave
will slide between the building ridge over the Great Lakes and round
the base of the low, crossing the lakes in the process. While the
resulting shot of colder air (850H temps -5 to -6C) will be enough
to maintain at least a chance for showers east/southeast of the
lakes through Sunday, moisture with this shortwave will be lacking.
This colder air could also support some wet snow mixing in at times
across the higher terrain areas during the day Sunday.

&&

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
Outside of a lingering shower or two east of the lakes early Sunday
night, a period of dry weather is expected overnight as a ridge of
high pressure crests over the forecast area and the low near the
Canadian Maritimes pushes out to sea. This dry stretch is expected
to be relatively short lived as the next trough will already be
impinging on the Great Lakes from the west Monday. There are typical
long range uncertainties in the strength, timing, and track of this
next system though a pair of frontal boundaries moving into the
region will lead to increased chances for rain later Monday and
Monday night. Colder air will begin spilling back across the lakes
Tuesday, leading to renewed chances for lake enhancement and upslope
showers east of the lakes through Wednesday. Temps could drop low
enough at the surface and aloft to support snow at the higher
elevations even during the daytime hours, though confidence is low
as the depth of this colder airmass remains in question...Stay tuned.

&&

.AVIATION /15Z THURSDAY THROUGH MONDAY/...
A strong cold occlusion has shifted into eastern New York this
morning. Rain shield associated with the boundary advancing across
eastern Lake Ontario region with widespread MVFR/IFR. A sharp dry
slot behind the boundary bringing a window of improving conditions
into western New York, although lake response rain showers off Lake
Erie area currently impacting KIAG this morning with a period of
MVFR.

The initial parent low over the central Great Lakes will give way to
secondary cyclogenesis off the southern New England coast Thursday
afternoon. This will allow deep moisture to wrap back into the area
from the east, with rain spreading back westward along with CIGS
lowering to MVFR/IFR. Rain will stay the main precip type for lower
elevations, but some wet snow may mix in across higher
terrain.

Outlook...

Tonight through Friday...Widespread IFR with periods of rain
and higher elevation wet snow.
Saturday...MVFR/IFR with a few rain and wet snow showers.
Sunday...VFR/MVFR with a chance of a rain or snow shower.
Monday...MVFR/IFR with rain and snow showers possible.

&&

.MARINE...
A lull in the sfc pressure gradient will pinwheel across the Lower
Great Lakes region today, as separate areas of low pressure
will be found over the Mid western states and off the coast of
New Jersey. This will allow winds and waves to quickly subside.

Strengthening winds on the backside of the aforementioned coastal
storm will then result in strong north to northwest breezes
throughout the region late tonight and Friday. Widespread SCA`s
will likely be needed for this period.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Winter Weather Advisory from 6 PM this evening to noon EST
     Friday for NYZ012-019>021.
MARINE...None.

&&

$$

SYNOPSIS...EAJ/Hitchcock/TMA
NEAR TERM...EAJ/HSK/TMA
SHORT TERM...PP
LONG TERM...AR/PP
AVIATION...EAJ/Hitchcock/TMA
MARINE...EAJ/Hitchcock/RSH/TMA