Forecast Discussion for BUF NWS Office
776
FXUS61 KBUF 211453
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
953 AM EST Mon Jan 21 2019

.SYNOPSIS...
A northwesterly flow of bitterly cold air will result in dangerously
low wind chill values today along with another very cold night
tonight. The arctic airmass will finally move out of the area on
Tuesday. This will be followed by an area of surface low
pressure which will track to our north on Wednesday. This will
result in a short period of above normal temperatures along with
some mixed precipitation mid-week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Bitterly cold conditions will prevail through tonight.
Temperatures are crawling to the zero degree mark over the lower
terrain while still remaining below zero over higher terrain.
Expect a meager increase in temperatures today but with wind
chills still well below zero for continued wind chill warnings
and advisories.

Meanwhile, lake effect snow continues southeast of Lake
Ontario and to a lesser extent Lake Erie. These extend roughly
15 miles inland from the lakes. Much of this is inconsequential
in terms of amounts, but the cold airmass is making and meager
lift off the lakes is forming tiny flakes which are blowing
around together with the fresh snowpack already in place. This
has resulted in numerous accidents on both primary and secondary
roadways south of Lake Ontario. With this in mind, will keep a
winter weather advisory in place due to the poor conditions
remaining through this afternoon.

Surface high pressure centered across Ohio this evening will build
eastward across our region tonight. Winds will maintain longest east
of Lake Ontario, where wind chill headlines may have to be extended.
Wind chills aside, it will be another very cold night. Although
temperatures aloft will be considerably higher, the surface
high will provide conditions favorable for radiational cooling.
Temperatures will again fall below zero in most locations,
except along the immediate lakeshores. Lows should run 10 to 20
below across the North Country, with even colder readings
possibly in some spots. Otherwise, leftover lake snow showers
southeast of Lake Ontario should taper off to flurries while the
remainder will experience mainly clear skies.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
Tuesday will start very cold with a +2 SD surface high pressure
centered over the region. This surface high will slide to the mid-
Atlantic coastline through the day and a southerly flow will
commence a moderating temperature trend.

Tuesday night surface low pressure in the base of a mid level trough
will advance from the midwest to the central Great Lakes. A strong
LLJ will develop ahead of this low pressure, and this jet will aid
in rising temperatures through the night and bringing above freezing
temperatures to the region late Tuesday night and into Wednesday.

Precipitation wise, an initial broken area of light snow is possible
late Tuesday night on the leading edge of the LLJ. The precipitation
is then expected to become more widespread towards daybreak across
far WNY and the Saint Lawrence Valley as moisture deepens and the
surface low draws closer to our region. This precipitation will then
spread over the Genesee Valley and Finger Lakes region Wednesday.

This LLJ will bulge a layer of much warmer air aloft across WNY (850
hPa +2 to +5C) while surface temperatures around freezing lag
behind. A wintry mix is expected, with snow transitioning to
sleet/freezing rain as we warm aloft, and then plain rain briefly
spreading across WNY as surface temperatures warm into the upper 30s
to lower 40s. Cooler air to the north may linger the precipitation
as all snow across the North Country. Here there is potential for 2
to 4 inches of snow accumulation by Wednesday evening.

There is still uncertainty as to how fast and how much we warm
aloft...but for now will mention the risk of freezing rain in the
HWO for WNY. Of note, the recent extreme cold spell and prospects of
untreated roads may elevate the freezing rain potential...with
freezing rain on frozen ground surfaces that will lag behind in
warming.

By Wednesday night the surface low cutting to the north of Lake
Ontario will push a cold front across our region, changing the plain
rain back to all snow. This front will slowly move across our region
as a wave of low pressure will likely form on the front in the
South. As this wave rides northward, precipitation associated with
it may brush by our eastern zones.

Snow accumulation behind the front will be little to none for the
lower terrain, however higher terrain to the east of both lakes may
receive a few inches owing to lake enhancement and upslope
effects.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
The pattern will turn much more wintry again for the end of the week
and next weekend after our brief warm-up on Wednesday. The +PNA
pattern will re-amplify significantly by next weekend across the
North American continent, with a deep trough carving out in the
east. This will push temperatures to well below average again. This
cold pattern will have staying power, with long range outlooks and
ensembles suggesting it lasting through the end of the month and
beyond.

Looking at the details, on Thursday a complex frontal zone will
advance to the east coast. A wave of low pressure will be running
northeast along the boundary, and associated ascent from this wave
and the approaching mid level shortwave will likely allow
precipitation to linger on the cold side of the boundary. By
Thursday morning all areas should be back to snow, with some minor
accumulations possible. The synoptic snow will taper off from west
to east through the day, with some minor lake effect snow showers
possible later Thursday afternoon and Thursday night southeast of
the lakes as colder air aloft arrives. High temperatures Thursday
will be in the lower 30s in most locations, and lows Thursday night
will be in the upper teens to lower 20s.

Late Thursday night and Friday a strong mid level trough and
associated surface low/cold front will cross the region, marking the
leading edge of the return to much colder temperatures. This system
will bring a chance of snow showers areawide, with potential for
lake enhancement east of the lakes.

The cold becomes well established by the weekend. Model guidance
begins to diverge with the handling of clipper shortwaves moving
through the mean longwave trough, but in a general sense one or two
weak systems will continue to support light snow chances through the
weekend. There may also be lake effect potential next weekend,
although given the model differences with the handling of the
clipper systems there is a good deal of uncertainty with respect to
placement and strength.

High temperatures by the weekend will be back into the teens in most
locations, with lows in the single digits, and below zero east of
Lake Ontario.

&&

.AVIATION /15Z MONDAY THROUGH FRIDAY/...
A northwesterly flow of bitterly cold air will continue to
generate numerous bands of light lake effect snow southeast of
Lake Erie and Lake Ontario into this afternoon. Although snow
accumulation will be light, very small snowflakes will be
effective in lowering visibility. Conditions will vary anywhere
from MVFR to IFR in snow showers during this time. The most
persistent snows will be at KIAG/KROC/KJHW.

Conditions will improve late this afternoon as drier air moves
in and winds diminish. MVFR cigs will gradually dissipate with
mainly VFR conditions expected by this evening. High pressure
will build across the area late tonight with VFR flight
conditions.

Outlook...
Tuesday...VFR.
Tuesday night and Wednesday...MVFR/IFR in snow
changing to mainly rain.
Thursday...VFR to MVFR with scattered snow showers.
Friday...VFR to MVFR in scattered to numerous snow showers...
with IFR possible in more numerous snow showers east of the
lakes.

&&

.MARINE...
A relatively tight surface pressure gradient will remain in place
over the Lower Great Lakes through this evening. Winds will diminish
from west to east starting this afternoon as high pressure builds in
from Ohio. This will keep Small Craft Advisory conditions in place
throughout the Lower Great Lakes, with enough wave action to
continue to support the Heavy Freezing Spray Warning for Lake
Ontario.

The area of high pressure will drift across the Lower Great Lakes
tonight. This will allow winds, waves, and any lingering freezing
spray to diminish. Light winds will then gradually freshen over the
lakes during the day Tuesday, as the large surface high will move
east into New England.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Wind Chill Warning until 7 PM EST this evening for NYZ006>008-
     012>014-019>021-085.
     Winter Weather Advisory until 5 PM EST this afternoon for
     NYZ001>006.
     Wind Chill Advisory until 7 PM EST this evening for NYZ001>005-
     010-011.
MARINE...Small Craft Advisory until 1 PM EST this afternoon for LEZ040-
         041.
         Small Craft Advisory until 1 PM EST this afternoon
         for LOZ030.
         Heavy Freezing Spray Warning until 6 PM EST this evening
         for LOZ042>045-062>065.
         Small Craft Advisory until 1 AM EST Tuesday for LOZ042>044.
         Small Craft Advisory until 7 PM EST this evening for
         LOZ045.

&&

$$

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

NWS BUF Office Area Forecast Discussion