Forecast Discussion

Forecast Discussion for BUF NWS Office
000
FXUS61 KBUF 210619
AFDBUF

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

.SYNOPSIS...
A northwesterly flow of bitterly cold air will persist across our
region through Monday...and will continue to generate nuisance lake
snows and dangerously low wind chill values. Apparent temperatures
will tumble to between 20 and 30 below zero in many areas...and to
as low as 30 to 40 below across the North Country and interior
portions of the Southern Tier. The arctic airmass will finally move
out of our forecast area on Tuesday...and this will be followed by
a short period of above normal temperatures for midweek.

&&

.NEAR TERM /THROUGH TODAY/...
In the wake of last night`s winter storm...bitterly cold arctic air
will pour southward across the still relatively wide open waters of
Lakes Erie and Ontario overnight and Monday. This will not only keep
the lake snow machine fully engaged...but will also support wind
chill values that will drop to as low as 20 to 30 below zero in
many areas...with even colder wind chills of 30 to 40 below zero
found across the North Country and interior portions of the Southern
Tier. Consequently...Wind chill Advisories and Warnings remain in
effect for this potentially life threatening risk. The frigid wind
chills will be supported by 30 mph wind gusts and mercury readings
that will drop below zero across the majority of the region overnight...
including mins of 10 to 15 below across the North country. The only
area to stay above zero overnight will be in the areas of steadier
lake snow between Rochester and Syracuse.

Speaking of the lake snows...there are numerous narrow tendrils
of light lake effect snow continuing southeast of both lakes
during the early morning hours. While the intensity of these is
and will continue to be held greatly in check by both the short
northwesterly fetch and a rather stout capping inversion
situated between 3 and 5 kft (per a combination of data from the
00z KBUF sounding and available guidance)...our frigid airmass
will still guarantee the continued presence of countless such
bands right through the night. Since we will effectively lose
our dendritic growth zone in the arctic airmass...snowfall rates
from the resulting plates and columns will be under a half inch
per hour. This type of snow tends to be `greasier` as well for
those driving in it. It also is very effective in lowering
visibility. Fresh snowfall for the rest of the night will
generally be less than an inch...although an additional 1 to 3
inches will be possible for the counties lining the south shore
of Lake Ontario where a winter weather advisory remains in
effect. Again...the main concern overnight will be the low
temperatures and correspondingly dangerous wind chill values.
Limit outdoor exposure if possible.

On Monday...gusty northwest winds ahead of an approaching arctic
high will continue to generate concerning wind chills of 15 to 25
below...while actual air temperatures will be in the single digits
away from the immediate lake shores. Readings may remain below zero
across Lewis county. Otherwise...fairly widespread but light lake
snows will persist southeast of both lakes where new daytime
accumulations should remain under two inches.

The arctic surface high will drift across our forecast area Monday
night. While this will allow winds to subside across the region...
mins below zero away from the lake will still encourage wind chill
values to range from 15 to 25 below across the region. The current
wind chill headlines may have to be extended. Otherwise...leftover
lake snow showers southeast of Lake Ontario should taper off to
flurries while the remainder will experience mainly clear skies.
Stay tuned.

&&

.SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/...
A rebound from bitterly cold temperatures is expected during this
time period. On average, temperatures will warm by 15 to 20 degrees
Fahrenheit each day for Tuesday and Wednesday from where they were
the previous day. High temperatures on Tuesday, while still somewhat
below normal will be in the upper teens across the North Country and
in the mid to upper 20s across the rest of the area. Increasing warm
air advection ahead of an approaching area of low pressure will warm
the temperatures to above normal on Wednesday to the upper 30s and
low 40s for most areas. Low temperatures on Tuesday night will occur
early, and not cool much from daytime highs; lows across the area
will be in the low to mid teens across the North Country and in the
low to mid 20s across the rest of the area. Low temperatures on
Wednesday night will be in the mid to upper 20s across the area.

A large area of high pressure centered over the East Coast on
Tuesday morning will provide quiet weather for the day on Tuesday,
with chance POPs moving into far Western NY late in the evening.
Tuesday will start out cold, but as the area of high pressure shifts
east, southerly flow will increase over the area, helping to
increase warm air advection across the area and therefore
temperatures. A large ridge on the western side of the high pressure
will stretch from Mississippi Valley, eastward off the Atlantic
Coast. This ridge axis will cross the area on Tuesday afternoon. As
this ridge axis moves east, an area of low pressure will approach
the region from the Southern Great Lakes.

On Tuesday night, the area of low pressure approaching from the west
will track northeast to Lake Huron by Wednesday morning. As this
area of low pressure approaches the region, a warm front leading out
ahead of the system will cross the area overnight on Tuesday night,
causing widespread light snow to move into the area with cool
temperatures still in the area.

On Wednesday, light snow will start out the morning, and slowly mix
with and change to rain from west to east as temperatures warm. For
areas where the temperatures may stay cool enough, such as over the
higher terrain, precipitation may stay as a mix of rain and snow for
the entire day. The area of low pressure will move from Lake Huron
to Quebec through the day on Wednesday. A deep trough behind this
area of low pressure stretches from Western Ontario to the southern
tip of Texas.

Wednesday night, the area of low pressure will track east to
Northern New York, before another area of low pressure develops off
the Delmarva peninsula early Thursday morning. A cold front
associated with this area of low pressure will cross the area
Wednesday night, resulting in cold air advection and most of the
precipitation changing back over to snow before ending.

&&

.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 /06Z MONDAY THROUGH FRIDAY/...
A northwesterly flow of bitterly cold air will continue to generate
countless bands of light lake effect snow southeast of Lakes Erie
and Ontario through this morning. Although snow accumulation
will be light, the very small snowflakes will be very effective
in lowering visibility. Conditions will vary anywhere from MVFR
to LIFR in and out of these bands during this time. The most
persistent snows will be at KIAG/KROC/KJHW.

Conditions will improve this afternoon as drier air moves in
and winds diminish. MVFR cigs will gradually dissipate with
mainly VFR conditions expected by this evening.

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 Monday...as the region will be
squarely situated between an exiting storm over the Canadian
maritimes and an approaching area of arctic high pressure. 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.

The area of high pressure will drift across the Lower Great Lakes
Monday night. 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 11 AM EST this morning for
     NYZ001>006.
     Wind Chill Advisory until 7 PM EST this evening for NYZ001>005-
     010-011.
MARINE...Heavy Freezing Spray Warning until 6 AM EST early this morning
         for LEZ040-041.
         Small Craft Advisory until 1 PM EST this afternoon for
         LEZ040-041.
         Small Craft Advisory until 6 AM EST early this
         morning 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...JJR/RSH
NEAR TERM...Apffel/JJR/RSH
SHORT TERM...SW
LONG TERM...Hitchcock
AVIATION...Apffel
MARINE...JJR/RSH

NWS BUF Office Area Forecast Discussion