Rochester, New York 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

346
FXUS61 KBUF 180918
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
418 AM EST Sat Jan 18 2025

.SYNOPSIS...
A strong cold front will move across the region today. A mix of rain
and snow will accompany the front with all snow across the higher
terrain. Any rain will change over to all snow by tonight. Minor
accumulations are expected through tonight. Temperatures will
plummet through the first half of the new work week. The coldest air
in more than five years will build over the region Monday through
Wednesday and this will result in dangerously low wind chills
regionwide...along with accumulating lake snows east and northeast
of the lakes.

&&

.NEAR TERM /THROUGH TONIGHT/...
Water vapor imagery shows a deep trough digging into the Plains and
Upper Great Lakes region this morning. Cyclogenesis can be inferred
across the lower Tennessee Valley with increasing moisture
approaching the eastern Great Lakes region. A cold front extends
from an area of low pressure near James Bay and is draped across
northern Ontario into Illinois. Dry and mild conditions reside
across the forecast area early this morning, with some areas
climbing to the low 40s F across the lower elevations. Gusty winds
will be possible through morning.

Moisture will continue to move northward ahead of the approaching
strong cold front and surface low near the Tennessee Valley. Kata
frontal precipitation will enter far western NY around day break and
spread across the remainder of the forecast area through morning.
Based on thermal profiles, a mix of rain and snow will move into the
lower elevations while all snow will be found across the higher
elevations. A southwest wind will lead to downsloping across the
Finger Lakes region and therefore less precipitation is expected in
this area. Surface temperatures will fall a few degrees as
evaporative cooling occurs but with the cold front still to the
west, temperatures won`t move much through early afternoon. The
front will quickly cross the forecast area late this afternoon/early
evening. Winds will become westerly and surface temperatures will
take a nose dive behind the front. The strong low level jet will be
well to the east with weakening winds aloft as the front moves
through the region. Wind speeds will pick up some behind the front
but relax into the evening hours. The falling temperatures will
change any leftover precipitation to all snow across the lower
elevations. Most of the precipitation will be ahead of the front
which will limit issues.

A very dry airmass will move into the forecast area tonight. This
will erode the snow with only lingering snow showers across the
western Southern Tier and Tug Hill region. Plummeting temperatures
will result in low temperatures in the teens across western NY to
the single digits east of Lake Ontario overnight.

Snow accumulations will be elevation dependent today with 2-4"
across the higher terrain including the Chautauqua Ridge into the
Boston Hills/Ski Country. Similarly, the same can be said east of
Lake Ontario/Tug Hill. As rain transitions to snow later today 1-2"
is possible across the Niagara Frontier and hill tops of the Finger
Lakes region. Warmer temperatures and less snow will lead to little
to nothing in the Genesee Valley to the lower elevations of the
Finger Lakes region. Tonight, an additional inch or two is possible
across the higher terrain east of Lake Erie and on the Tug Hill.

&&

.SHORT TERM /SUNDAY THROUGH TUESDAY NIGHT/...
...FRIGID COLD WITH SIGNIFICANT LAKE EFFECT SNOWS EARLY NEXT WEEK...

On Sunday deep upper level troughing will continue to strengthen its
grip on central and eastern North America...with its attendant pool
of arctic air spreading across the Upper Midwest and Upper Great
Lakes. Meanwhile at the surface...the cold front that passed through
our region Saturday will serve as the focal point for secondary
surface cyclogenesis along the Carolina coastline...with this low
then expected to track northeastward off the mid-Atlantic coastline
by late Sunday...then to the Canadian Maritimes by Monday morning.
The Canadian GEM continues to be a western outlier with the track of
this low compared to the other guidance...with the latter therefore
being leaned on more heavily again with this forecast. Based on the
latter...still expect any true direct impacts from the coastal
system to remain well to our south and east...though there will
still be at least a chance of snow areawide Sunday into Sunday
evening along both the western fringes of this passing system and
lake-aggregate thermal troughing extending back northwestward across
the Great Lakes. Lake enhancement and localized convergence along
this latter feature will lead to a better likelihood of snow south
of the lakes Sunday afternoon into Sunday evening...where some
locally enhanced amounts of 1-2" will be possible...with amounts
elsewhere generally up to an inch or so. Otherwise...it will be
notably colder on Sunday than the preceding couple of days...with
highs struggling to climb above the mid teens to lower 20s.

As the low pulls north of our latitude Sunday night and Monday...it
will help to pull the pool of arctic air to our west across the rest
of the Great Lakes and Northeast...with the initially weak northerly
low level flow gradually backing to 250/260 degrees and gaining
strength over time...with this first taking place off Lake Erie
later Sunday night and Monday...then off Lake Ontario Monday and
Monday evening. The resulting increase in fetch coupled with an
increasingly favorable thermodynamic environment (lake-induced
equilibrium levels climbing to between 11 and 13 kft AGL) will allow
initially weaker lake effect and upslope-driven snows Sunday evening
to gradually lift northward to areas east of the lakes through
Monday/Monday evening while consolidating/strengthening into more
dominant single bands. Off Lake Erie...this will result in lake
snows gaining strength across the southern Tier later Sunday
night...before further organizing and lifting northward to areas
between northern Chautauqua/Cattaraugus counties and the Buffalo
southtowns/southern Genesee county during Monday. Off Lake Ontario
this process will take place a bit later...with organizing activity
southeast of the lake Monday morning further consolidating and
lifting northward to the vicinity of the Tug Hill Monday afternoon
and evening.

While the guidance suite continues to exhibit some subtle
differences in the orientation in the low level flow Monday night
and Tuesday...there is reasonable agreement on a general westerly to
west-southwesterly flow remaining in place across the area for this
24-hour period...with the latest guidance having also trended a just
little more west-southwesterly than what was seen yesterday. This
would keep the lake snows going across areas east and east-northeast
of the lakes...with the activity perhaps even lifting a little bit
further north during the day Tuesday. Gradual veering of the low
level flow Tuesday night attendant to the approach and passage of
the main upper level trough axis would then tend to send the lake
snows back southward...with the shortening fetch and some drying/
decrease in lake EQLs attendant to the approach of low-level ridging
leading to some weakening as we push through the night.

With respect to potential accumulations from the lake snows from
later Sunday night onward...these are still somewhat tough to pin
down given continued uncertainties in the orientation of the low
level flow...which will directly influence band placement and
consequently residence time. Given the very cold airmass...the main
dendritic snow growth zone also looks to largely lie underneath the
areas of strongest lift/richest moisture for much of the event...
which could have at least some negative influence on snowfall rates.
This being said...the otherwise favorable thermodynamics and fetch
along the long axes of both lakes both suggest the potential for
significant lake snows... particularly off Lake Ontario where the
overall setup looks better and where favorable orographics from the
Tug Hill also look to come into play from late Monday through
Tuesday. At this point...early projections suggest the potential for
a bit over 2 feet of snow across the Tug Hill region east of Lake
Ontario...with a larger surrounding envelope of 1-2 foot
accumulations including the Watertown area. Meanwhile off Lake
Erie...a swath of 1-2 foot accumulations appears likely from
northern Chautauqua/Cattaraugus counties into Southern Erie
county...with amounts of 8-16" possible as far north as the Buffalo
Southtowns and southern Genesee County. With this in mind...Winter
Storm Watches for Lake Effect Snow have been issued as outlined
below.

While the above look to be the main lake effect areas during this
event...it should also be mentioned that there`s at least some
potential for at least some headline-worthy snows southeast of Lake
Ontario later Sunday night and Monday as the Lake Ontario activity
gets better organized. This being said...confidence in this is much
lower at this point...as do appear potential amounts. With this in
mind have held off on any additional headlines for now...though this
potential will need to be monitored as we push through the weekend.

Otherwise...expect bone-chilling cold to develop during this period
as 850 mb temps in the negative teens Sunday plunge to around -20C
by the start of Monday...then to potentially as low as -25C or so
for Monday night and Tuesday. This will result in high temperatures
struggling to get much above the upper single digits to mid teens
Monday...and then the single digits to about 10 to 12 above zero on
Tuesday. Meanwhile lows in the single digits to around 10 above
Sunday night will fall to the 5 below to 5 above zero range Monday
night...and to the negative single digits in areas away from the
lakeshores/lake snows Tuesday night. Coupled with expected winds...
this will result in apparent temperatures dipping into the -15 to -
25 range at times from later Monday through Tuesday night...which
will likely eventually necessitate the issuance of some Cold Weather
Advisories.

&&

.LONG TERM /WEDNESDAY THROUGH FRIDAY/...
A sfc-850H ridge will build over the lakes Wednesday into Thursday.
This will not only help to continue to weaken and shift the overall
lake response further north...but will also lead to a warming trend.
That is to say, temperatures are expected to remain below normal,
though highs Thursday and Friday are expected to range in the 20s as
opposed to single digits.

&&

.AVIATION /09Z SATURDAY THROUGH WEDNESDAY/...
A southerly low level jet and VFR conditions will continue across
western and north central NY this morning. Wind gusts around 25 kts
are possible at the TAF sites with higher gusts along the Lake Erie
shoreline. Low level wind shear will be present for those places not
mixing by daybreak.

A strong cold front will move across the region later today.
Precipitation will move into western NY this morning and spread east
across the forecast area. Marginal surface temperatures will result
in a rain and snow mix at lower elevations and snow across higher
elevations including KJHW. Flight conditions will deteriorate and
widespread MVFR/IFR conditions are expected at the TAF sites. Model
guidance is showing a lot of IFR conditions this afternoon. Leaned
less aggressive in pre-frontal conditions as downsloping will likely
keep them at MVFR.

Any mix of rain and snow will transition to snow late this afternoon
into the evening. Widespread snow will move east with lingering lake
effect and upslope snow showers tonight. MVFR/IFR conditions will
continue across the TAF sites tonight.

Outlook...

Sunday...VFR/MVFR with a chance of snow showers.
Monday through Wednesday...Local LIFR in lake effect snow east
of the lakes, mainly VFR elsewhere.

&&

.MARINE...
Occasional moderate southwest to west winds will continue to bring
Small Craft Advisory conditions on Lake Erie much of the time today.
A cold front will move across the Lower Lakes this afternoon into
this evening. West winds will briefly pick up with a brief period of
Small Craft Advisory conditions on the southern shore of Lake
Ontario this afternoon through tonight. Winds relax on the Lakes
late tonight through Sunday night.

A prolonged period of Small Craft Advisory conditions will occur
next week.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Winter Storm Watch from Monday afternoon through Wednesday
     morning for NYZ006>008.
     Winter Storm Watch from Monday morning through late Tuesday
     night for NYZ010-011.
     Winter Storm Watch from late Sunday night through Wednesday
     morning for NYZ012-019-020-085.
MARINE...Small Craft Advisory until 10 PM EST this evening for LEZ040-
         041.
         Small Craft Advisory from 1 PM this afternoon to 8 AM
         EST Sunday for LOZ042.
         Small Craft Advisory from 6 PM this evening to 8 AM EST
         Sunday for LOZ043-044.
         Small Craft Advisory until 8 AM EST Sunday for LOZ045.

&&

$$

SYNOPSIS...HSK/RSH
NEAR TERM...HSK
SHORT TERM...JJR
LONG TERM...PP
AVIATION...HSK
MARINE...HSK