Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 181151
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
651 AM EST Thu Jan 18 2018

.SYNOPSIS...
Lake effect snows will return to portions of the forecast area
today. Snow showers will linger longest east of Lake Ontario, into
Friday morning, as an upper level disturbance transits the area
tonight. Temperatures will begin to rise on Friday, with mild
readings in the 40s by the weekend thanks to the development of
broad southerly flow around high pressure over the Southeast. The
influence of the high should keep most areas dry for much of the
weekend before a low pressure system tracking across the central
U.S. brings wet weather to start the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
A narrow ridge extending northeast off of high pressure centered
over the lower Mississippi valley has crossed the area overnight,
and this ridge has suppressed any lake effect activity thus far, in
spite of regional satellite imagery that continues to show a plume
of lake effect clouds streaming off of Lake Ontario.

While things have been quiet overnight, expect lake effect snow
showers to ramp back up again as we move through the morning hours
as the surface ridge moves off to the east. WV imagery shows a
relative increase in moisture upstream, supporting NAM BUFKIT
profiles that show an increase in 925-850mb moisture after 12Z.
While this moisture layer is shallow, it is positioned within the
-12 to -18C dendritic growth zone, and with persistent cold air in
the low levels on southwesterly low level flow, it is expected that
we will see lake effect showers develop as this nominally more moist
airmass infiltrates the region. While mesoscale models continue to
downplay this lake effect scenario, it is worth noting that they
also missed yesterday`s lake effect snows, likely due to the very
shallow nature of the airmass involved. With that in mind, this
forecast continues to support 2-3 inches of low-density, fluffy snow
across the Buffalo metro today, with a few more inches east of Lake
Ontario, where accumulations are enough to warrant continuing a
winter weather advisory.

In addition to the snow, the continued presence of a tight gradient
across the region will continue to produce strong winds aloft that
will have no trouble mixing down to the surface today, producing
winds gusting to 35 mph. This may reduce visibilities considerably
where snow is falling, while drifting of snow across roadways may be
an issue even where snow is not falling. The winds will also make
for another raw day across the area, with wind chills remaining in
the single digits across much of the forecast area, even with highs
that will top out in the low to mid 20s.

A well-defined, but weakening upper level disturbance will cross
the region tonight, helping to maintain snow showers east of Lake
Ontario. Moisture with this feature, and thus the bulk of any shower
activity will likely remain confined to the northern half of the
forecast area, while developing warm advection should shut off any
lingering lake effect showers off of Lake Erie this evening.
Temperatures will change little overnight, thanks to aforementioned
warm advection.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
High pressure centered over the Southeast states Friday will ridge
north into southern NY beneath expanding mid-level ridging over the
eastern Great Lakes. Lingering cool air at 850mb (-12C) Friday
morning should continue to support some lingering lake
enhanced/upslope snow showers east of Lake Ontario before
ending/tapering off later in the evening as surface and midlevel
ridging increase subsidence over the area. There is a lower risk of
potentially some freezing drizzle as thermal profiles show moisture
confined to below the dendritic snow growth zone. Otherwise, outside
of this limited lake effect, expect dry weather Friday. Warm air
advection aloft will help push temperatures back to near normal
levels with Highs expected to reach within a few degrees either side
of the freezing mark.

A 50-60kt low level jet is forecast to shift over western and
central NY Friday night. While the warm advection should keep the
highest gusts from mixing down to the surface, surface gusts beneath
the inversion per BUFKIT data should run around 40 mph with a tight
pressure gradient across the eastern Great Lakes. Temps Friday night
should rise a few degrees overnight in response to continuing warm
air advection under strengthening southwest flow.

Saturday, a lingering tight pressure gradient will result in
continued gusty winds to around 40mph especially across the Niagara
Frontier. Ridging over our region should promote dry weather with
only a slight chance for a rain shower on the Tug with westerly
upslope flow. The low level jet will boost 850mb temps above 0C for
the weekend which should help surface highs to push to near or into
the 40s. Winds will slacken Saturday night with the relaxing of the
pressure gradient and departure of the low level jet. Mostly cloudy
skies will keep overnight lows limited to within a few degrees
either side of the freezing mark.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
Sunday and Sunday night, a zonal mid-level flow with moisture
connection from the Gulf of Mexico along with increasing low level
southwesterly flow across Western and Central NY will bring similar
mild temperatures ahead of low pressure lifting out of the Central
Plains states. Warm air and moisture advection will bring increasing
chances of western NY rain and North Country possibly wintry mix
ahead of the low. POPs spread from the western Souther Tier north
and east later Sunday into Sunday night. Highs in the upper 30s to
low 40s Sunday will only slip a few degrees into the 30s Sunday
night. This may pose a problem east of Lake Ontario of temps dip
below freezing in the presence of rain.

The warm front is forecast to be over the North Country on Monday
where likely POPs for rain or rain/snow/mix have been placed. Just a
chance of rain in WNY behind the warm front and ahead of an
approaching cold front. Highest POPs in the long term (Likely) in
place Monday night where a cold front and low level jet, tied to low
pressure lifting across the western Great Lakes, is forecast to
cross our region. Thermal profiles support plain rain across western
NY with rain/snow or possible wintry mix in the North Country. PWATs
near 3/4 of an inch should bring some moderate to possibly heavy
rainfall.

Tuesday into Wednesday, Cooler air will rush back into the region
with blustery southwest to west winds behind the cold front. This
will bring a return to more seasonable mid-winter temperatures for
mid-week along with the potential for more lake effect snow within
wraparound moisture and lowering 850mb temps.

&&

.AVIATION /12Z THURSDAY THROUGH MONDAY/...
WV imagery shows increasing moisture across the region this morning.
This will allow for lake effect snow showers to develop ENE of the
lakes between 12-15Z, with IFR conditions in -SHSN persisting at
KART/KBUF through much of the day Thursday, while mainly VFR
conditions will persist outside of lake effect areas through most of
the period. An upper level disturbance will cross the lower Great
Lakes tonight, bringing a chance for more scattered snow showers and
associated MVFR conditions, with IFR conditions across higher
terrain east of Lake Ontario.

Outlook...

Friday...MVFR with a chance of snow showers E of Lake Ontario. VFR
elsewhere.
Friday night through Sunday...Mainly VFR.
Monday...Mainly VFR with a chance of rain showers.
Tuesday...IFR with rain early changing to lake effect snow late.

&&

.MARINE...
A persistent pressure gradient will maintain brisk west-
southwesterly flow across the lakes into the upcoming weekend, and
small craft advisories remain in place into Saturday. High pressure
nosing across the region will relax the winds Sunday before winds
freshen once again on Monday ahead of a strong low pressure system
tracking out of the central Plains.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Winter Weather Advisory until 7 AM EST Friday for NYZ006>008.
MARINE...Small Craft Advisory until 10 PM EST Saturday for LEZ040-041.
         Small Craft Advisory until 4 AM EST Sunday for
         LOZ042>045.

&&

$$

SYNOPSIS...WOOD
NEAR TERM...WOOD
SHORT TERM...SMITH
LONG TERM...SMITH
AVIATION...WOOD
MARINE...WOOD


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