Forecast Discussion

Forecast Discussion for BUF NWS Office
000
FXUS61 KBUF 252343
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
643 PM EST Sat Jan 25 2020

.SYNOPSIS...
A complex weather system moving through the Great Lakes region will
bring mixed precipitation to the region early tonight before colder
air gradually changes the precipitation over to snow late tonight
and Sunday. Most areas should pick up an inch or two of snow
accumulation by the end of the weekend with parts of the
Southern Tier and Eastern Lake Ontario region receiving several
inches.

&&

.NEAR TERM /THROUGH SUNDAY/...
A complex storm system over the Great Lakes will continue to support
precipitation over the region tonight. The parent low within the
broad storm system will be centered near Lake Huron tonight...while
a secondary low will make its way up the coast of New England. As
the axis of this double barrelled system moves north of Lake
Ontario...colder air will move back across our region. This will
gradually allow the remaining rain to change to a bit of wet snow.
The changeover will first take place across the higher terrain of
the Srn Tier and Lake Ontario region. A wet, slushy inch or so of
accumulation may stick to grassy and elevated surfaces across the
Srn Tier by daybreak Sunday...with a couple inches of accumulation
on the Tug Hill. Most other areas should not pick up more than a
coating.

The weak surface low will then track past the Lower Lakes as it
heads off to Maine on Sunday. While there will be ongoing light snow
favoring the higher terrain of the western Southern Tier and Tug
Hill, accumulations will again be minor as 850mb temperatures will
only be in the neighborhood of -6C to -7C. Add to that, marginal
surface temperatures which will again hamper snowfall accumulations.
Therefore, only an additional inch or so through mid afternoon is
expected across the higher terrain. Elsewhere, less than an inch if
much at all. Late Sunday afternoon, another round of moisture
pivoting around the upper level low will bring a better chance of
accumulating snowfall. Upslope flow (westerly flow) and the above
mentioned arrival of additional moisture, along with a secondary
upper level trough forecast to move through Sunday night will likely
bring the greatest potential for accumulating snowfall. Otherwise,
total daytime accumulations will be light Sunday with the potential
of only 1-3 inches at best across the higher terrain.

In terms of temperatures, which will play a critical role in
accumulation will likely peak in the mid 30s for lower elevations to
low 30s across higher terrain.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/...
Stacked low pressure over southern Quebec will continue to track
east Sunday night. A shortwave trough will round the base of the
upper low Sunday night and upward motion will increase across the
eastern Great Lakes region. Moisture will increase allowing
temperature profiles to saturate through the dendritic growth zone.
There is a lack of cold air behind this trough that moves through so
cold air advection will be very weak overnight. Temperatures at
850mb fall to around -8C by Monday morning which is marginal for
lake enhancement across Lakes that are 35-38 F. Westerly flow turns
northwesterly overnight and ongoing snow showers across the region
will become enhanced across the higher terrain east of both Lakes.
Temperatures will also fall to the upper 20s across the higher
terrain east of both Lakes to the low to mid 30s across the Lake
Plains. These marginal surface temperatures across the lower
elevations will keep snowfall accumulations light. Accumulating snow
is expected across the higher terrain with amounts of 4-7 inches on
the Tug Hill and 3-6 inches across the Chautauqua Ridge and
Cattaraugus, southern Erie and Wyoming counties. The best timing for
accumulating snow across the higher terrain will be Sunday evening
through Monday morning. This may warrant an Advisory in future
updates.

Northwest flow continues on the backside of the departing shortwave
trough Monday. Snow showers will continue across the region with
orographic enhancement on the higher terrain. Upstream moisture will
diminish through the day as northwest flow continues. An additional
1-2 inches is possible across the higher terrain to less than inch
across the lower elevations. High temperatures will reach the low
30s across the higher terrain to the mid 30s across the lower
elevations.

Diminishing snow showers are expected Monday night. Low temperatures
will fall to the low to mid 20s.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
Tuesday an upper level trough and weak surface trough will drop
across our region, ushering in a cooler airmass. Point soundings
display a wealth of moisture around 3-5K feet, however this is well
below the dentritic snow growth zone...and with marginal 850 hPa
temperatures of -7 to -8C any snow showers or lingering lake snows
will be limited.

Surface high pressure will slowly build eastward from the
midwest...arriving over our region by Thursday morning. Seasonable
daytime high temperatures will turn cold both Wednesday night and
Thursday night when interior locations will drop into the single
digits to below zero.

The next weather maker will be next weekend, when both a northern
and southern stream shortwave transverse the U.S.. The global models
still have timing differences, with the 12Z GFS faster than the
ECMWF. At this time both models keep the southern feature the main
player as far as precipitation...with a track to our east and
limited synoptic snows.

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
A slow moving storm system in the vicinity of Lake Huron will move
to the north of the region on Sunday. This will generally keep
unsettled weather across our forecast area...with widespread MVFR to
IFR cigs expected through the TAF period. The cloud cover will be
accompanied by rain showers that will become increasingly mixed with
snow overnight before changing to mainly snow during the day Sunday.
Vsbys will drop to LIFR in areas of snow Sunday.

Outlook...

Sunday night...IFR to MVFR with fairly widespread snow showers.
Monday...IFR to MVFR cigs slowly improving to VFR.
Tuesday...Mainly VFR...but MVFR in scattered snow showers.
Wednesday and Thursday...Mainly VFR.

&&

.MARINE...
As the axis of a surface trough pushes north of Lake Ontario
tonight...stronger cold advection and a tighter sfc pressure
gradient will encourage southwest winds to freshen across the
region. This will lead to small craft advisory conditions on Lake
Erie overnight with a general offshore flow on Lake Ontario
postponing new SCAs until at least Sunday.

Continued strengthening of the winds on Sunday will lead to fresh to
strong southwesterlies on both lakes. SCAs will likely be needed for
all of the NY nearshore waters of Lake Ontario...especially north of
Mexico bay on the east end of the lake where the flow will favor
higher wave action.

As the center of the slow moving storm system exits across Quebec
and the Canadian maritimes Sunday night and Monday...winds and waves
will gradually subside across the region.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Winter Weather Advisory until 6 AM EST Monday for NYZ006>008.
MARINE...Small Craft Advisory from 1 AM Sunday to 10 AM EST Monday for
         LEZ040-041.

&&

$$

SYNOPSIS...RSH
NEAR TERM...AR/RSH
SHORT TERM...HSK
LONG TERM...Thomas
AVIATION...RSH
MARINE...RSH

NWS BUF Office Area Forecast Discussion