Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 201143
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
643 AM EST Sun Jan 20 2019

.SYNOPSIS...
A major winter storm will produce heavy snow into this morning,
which will taper off this afternoon as the storm exits into New
England. Expect poor travel conditions today, due to snow and areas
of blowing snow. Frigid air on the backside of the storm will also
support dangerously low wind chill values, particularly late this
afternoon through Monday.

&&

.NEAR TERM /THROUGH MONDAY/...
At 6 a.m. low pressure was centered across SE Pennsylvania with
3 hour pressure falls suggesting this low will track toward
Cape Cod this morning. Radar shows heavy snow across the eastern
Lake Ontario region early this morning, but this will continue
to slide eastward out of the area through the morning hours.
Meanwhile, the back edge of the synoptic snows is just west of
Niagara County, and this will also progress eastward this
morning, with diminishing snowfall rates across Western New
York.

Large scale synoptic lift from mid-level warm air advection,
favorable jet dynamics, and a shortwave will result in widespread
snowfall this morning. This will diminish from west to east
following the eastward movement of the low and associated shortwave.
However, 850mb temperatures around -10C this morning will rapidly
drop to around -25C by late this evening. This will support lake
effect snow which will develop behind the departing synoptic snows.
Upstream moisture will be limited, but moderate instability will
support persistent multiple bands southeast of the lakes today and
tonight. Snowfall rates will be light to moderate, but still ample
to add on an additional several inches in some areas both this
afternoon and again tonight. This should be fairly close to the
southeast shores of Lake Ontario where the longer fetch will help
offset dry upstream air. One possible limiting factor to higher
accumulations will be the character of the snow, which will likely
be plates and columns which tend not to accumulate as quickly.

There will continue to be a brisk N-NW flow today with wind gusts of
25 to 35 mph for much of the day. This will result in areas of
blowing and drifting snow - even in locations where the snow tapers
off. It also will be cold, with temperatures falling into the single
digits. This combined with the winds will result in wind chills of
below zero wind chills today, especially across the North Country
where wind chills will be about 25 below today.

The storm system will track across the Canadian maritimes tonight
while a large arctic high will build across the Upper Great Lakes.
The combination of wind and cold will result in dangerously cold
wind chills tonight. Wind chill values will drop to 20 to 30 below
in most areas, with values as low as 40 below east of Lake Ontario.
Temperatures will not rebound much on Monday, with highs only in the
single digits (and even below zero across the North Country).
Meanwhile, there still will be a tight pressure gradient with
bitterly cold conditions during the day on Monday. Wind chill
warnings and advisories were issued as outlined below for tonight
and Monday. This will be the coldest conditions our region has
experienced for some time, and poses a serious risk for those who
even spend a brief period of time outdoors.

Otherwise, lake effect snow will linger southeast of the lakes
Monday, with light additional accumulation likely to be in the 1 to
3 inch range.

&&

.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/...
A bitterly cold night is expected Monday night as surface high
pressure expands eastward from OH and across our region. While the
cold air aloft (850 hPa T`s -20C) shifts eastward the clearing skies
and light winds over a fresh snowpack should allow for nearly the
entire region to drop to around 0F and lower. A few lake clouds SE
of Lake Ontario may hold a few areas on the positive side of zero.
Otherwise the traditional colder areas of the So. Tier may near -10F
before high clouds build in late...and areas east of Lake Ontario
which should remain clear through the night bottom out -10 to -20F.

Winds will be diminishing through the night as the surface high
pressure nears. There may need to be an extension to the current
wind chill headlines, but for now will only mention the cold
temperatures and possible headline worthy wind chills in the HWO.

Tuesday a surface high will cross the region with fair weather, and
surface temperatures not as cold as a light southerly flow develops
behind the surface high. In fact these southerly winds will only
increase Tuesday night as a 60 knot LLJ develops. A strengthening
surface inversion will likely limit these stronger winds from mixing
to the surface. Surface temperatures will climb into the lower 20s
east of Lake Ontario, and to near 40F across the lower elevations of
WNY Tuesday night. A warm front passing across the region Tuesday
night will bring a return to some light snow that will likely mix
with some rain late across the lower terrain of WNY.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
Wednesday, a mid level trough and associated surface low will move
into the Central Great Lakes and then into Quebec. Strong warm
advection ahead of the system will allow temperatures to continue to
rise through the late morning hours of Wednesday. Expect the snow to
change to plain rain for most areas Wednesday as temperatures rise
into the upper 30s to lower 40s briefly. There may be a brief period
of freezing rain during the transition as a frozen ground will lag
behind the warming air temperatures. The cold front moves across the
area Wednesday afternoon, allowing any lingering rain showers to
change back to snow showers Wednesday night as colder air moves back
into the region. Temperatures will drop back into the upper 20s by
late Wednesday night.

Forecast uncertainty begins to increase by Thursday and into next
weekend. There will be a trailing southern stream trough and surface
low along the cold front over the southeast states Wednesday night
and Thursday. This low will try to move up the eastern seaboard,
although the current GFS and ECMWF runs keep the subsequent system
too far east to impact our area. Some previous runs of both models
had this low wrapping up and taking a farther west track, which
would then impact our area on Thursday.

Behind this potential system, it will turn steadily colder Friday
and Saturday. A mid level trough and associated cold front will
cross the area Friday with a chance of snow showers. Westerly flow
may develop Friday night and Saturday in the wake of this trough,
with increasing lake effect snow potential east of the lakes.
Temperatures will be well below average again by next weekend.

&&

.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
Conditions will improve from west to east this morning. The back
edge of the steady synoptic snow is just west of KIAG for the
12Z TAF cycle, but with colder air aloft this will be replaced
by lake effect snows south of the lakes. With dry air upstream
this should be light to moderate, but still enough to result in
predominantly IFR conditions at KROC all day, and possibly at
KIAG/KJHW as well. At KART moderate to heavy snow will taper off
late morning, with conditions improving to MVFR this afternoon
with no lake effect snow due to northwesterly winds.

There will be lake effect clouds and light snow southeast of the
lakes tonight. Snow will be very light at most locations, but
will be a bit steadier at KROC. Expect mainly MVFR conditions
tonight, with periods of IFR possible at KROC.

Outlook...
Monday...Localized IFR in lake effect snow showers southeast of
the lakes...with MVFR elsewhere.
Tuesday...VFR. Tuesday night and Wednesday...MVFR/IFR in snow
changing to mainly rain.
Thursday...VFR to MVFR with some snow showers likely.

&&

.MARINE...
Strong north winds will shift to the northwest today as low pressure
tracking to the New England coast strengthens. Latest guidance shows
stronger winds for Monday with a tight pressure gradient between the
departing coastal storm and arctic high pressure moving into the
Central Great Lakes. As a result small craft headlines were extended
for most of the waters. With stronger winds and more wave action,
the Heavy Freezing Spray warning was also extended through Monday
for Lake Ontario.

Winds will diminish Monday night when arctic high pressure builds
across the region.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Winter Storm Warning until 6 PM EST this evening for
     NYZ001>008-010>014-019>021-085.
     Wind Chill Warning from 6 PM this evening to 7 PM EST Monday
     for NYZ006>008-012>014-019>021-085.
     Wind Chill Advisory from 6 PM this evening to 7 PM EST Monday
     for NYZ001>005-010-011.
MARINE...Heavy Freezing Spray Warning until 6 AM EST Monday for LEZ040-
         041.
         Small Craft Advisory until 1 PM EST Monday for LEZ040-041.
         Small Craft Advisory until 10 AM EST this morning for
         LEZ020.
         Small Craft Advisory until 6 AM EST Monday for LOZ030.
         Heavy Freezing Spray Warning until 6 PM EST Monday for
         LOZ042>045-062>065.
         Small Craft Advisory until 1 AM EST Tuesday for LOZ042>044.
         Small Craft Advisory until 7 PM EST Monday for LOZ045.

&&

$$

SYNOPSIS...Apffel
NEAR TERM...Apffel
SHORT TERM...Thomas
LONG TERM...Hitchcock/Thomas
AVIATION...Apffel
MARINE...Apffel



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