Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 231946
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
246 PM EST Thu Nov 23 2017

.SYNOPSIS...
A shortwave and weak frontal boundary will help enhance some weak
lake effect showers north and east of Lake Ontario this evening, and
to a lesser extend off of Lake Erie. High pressure will bring a
quiet but mild day Friday ahead of a cold front passage Friday night
into Saturday morning with scattered rain showers. Some weak lake
effect is then possible again southeast of the lakes Saturday night
into Sunday with only minor accumulation.

&&

.NEAR TERM /THROUGH FRIDAY/...
A mid level shortwave seen in WV imagery over the upper Great Lakes
will track across the lower Great Lakes this evening. The continue
height fall aloft and ascent ahead of the wave will help to enhanced
a minor lake response northeast of Lake Ontario and to a lesser
extend off of Lake Erie. While most the area will remain dry this
afternoon and evening, the lake response will bring some rain
changing to snow showers northeast of Lake Ontario, with light snow
accumulations around an inch over the higher terrain. Otherwise,
less favorable lapse rates and drier air near Lake Erie will keep
the lake response limited to some flurries/sprinkles early with a
few light rain turning to snow showers this evening. A light dusting
in the Boston Hill is possible, although not expected.

Otherwise, the weak ascent with the wave quickly departs to our east
overnight with drier air quickly building back in across the lakes.
Any lake response will diminish overnight, yielding a dry start to
the day Friday with just some lingering low-level lake clouds. High
pressure will slide to our east with the thermal ridge axis arrive
into western NY late in the day Friday. This will allow for
overnight low temperatures around 30 to quickly climb to the upper
40s to low 50s on Friday. The warmest temperatures will be found in
the typical downslope regions across the lower Genesee Valley and
Northern Finger Lakes.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
Mid level trough will dig east into the Great Lakes and Ohio Valley
Friday night into Saturday. Weak cold front associated with this
upper level feature will push east through the region Friday night
into Saturday morning. Moisture is limited, so for the most part,
light rainfall amounts are expected. A deep southerly flow ahead of
the front will keep temperatures from dropping off much Friday night.

Colder air will be slow to deepen behind the front, with the better
part of Saturday likely to be dry outside of lingering showers with
the front and associated shortwave.

A secondary cold front crosses the lower Great Lakes late in the day
Saturday which will allow for better lake responses. Temperatures
aloft will gradually fall behind the front, perhaps just cold enough
for some light lake effect rain or snow showers by Saturday evening.
Accumulating snows may not occur until later Saturday night into
Sunday when 850 mb temperatures drop to near -6C, but even at then
over-lake instability is not overly impressive. Snow amounts should
be on the light side given the marginal over-lake instability. The
best chances for minor accumulations will be in favored west-
northwest flow areas of the Chautauqua ridge, and areas southeast of
Lake Ontario from Rochester to Oswego. While accumulations are
expected to be on the lighter side, it still could make untreated
roadways more difficult to navigate. In addition, BUFKIT profiles
indicating plentiful low level moisture will be available through
the night even with lake induced equilibrium levels crashing below
5kft. This could be a set up for some freezing drizzle as surface
temperatures will be below freezing and lingering moisture will be
below the dendritic snow growth zone. This will need to be monitored
over the next few days.

&&

.LONG TERM /MONDAY THROUGH WEDNESDAY/...
Surface and mid-level ridging will build across western and central
New York Monday. Expect dry weather with low clouds breaking for
some sun on Monday. Temps with the riding aloft will make a run into
the low 40s across WNY but likely linger in the 30s east of Lake
Ontario.

The surface and mid-level ridge axis shift east of our area by
Tuesday with southerly flow picking up ahead of what the GFS/GEM
show as another cold frontal passage for Tuesday night/Wednesday.
The ECMWF however does not show a front crossing our region. With
these differences in mid have only brought in slight chance POPs for
Tuesday night with Tuesday expected to largely be dry. The global
models do show a strong 50 knot low level jet crossing our region
Tuesday which could lead to some gusty winds with diurnal mixing.
Temps Tuesday under Southerly flow may make a run toward the upper
40s to low 50s with clouds possibly increasing from the west if the
GFS is correct with the approach of a front. Wednesday continues a
spread in guidance with the GFS/GEM showing -10C 850mb temps behind
a cold front and the EC showing +2C to +6C in zonal flow. Have
leaned toward GFS/GEM with chance POPs while surface temps have a
high bust potential with such spread. Have leaned toward a blend of
guidance for now yielding mid to upper 40s for highs but cloud be
cooler especially if the cold frontal passage occurs.

&&

.AVIATION /20Z THURSDAY THROUGH TUESDAY/...
Primarily MVFR CIGS will prevail downstream from the lower Great
Lakes this afternoon, with most locations seeing some improvement to
VFR this evening and overnight. Some light lake enhanced rain
changing to snow showers are possible near KART this evening, with
localized MVFR restrictions. VFR conditions will prevail on Friday
with high pressure in control.

Outlook...

Saturday...VFR/MVFR with rain showers likely.
Sunday...Mainly MVFR, localized IFR in -SHSN SE of the lakes.
Monday and Tuesday...VFR.

&&

.MARINE...
Small Craft Advisories are in place, as the pressure gradient
increases this afternoon. In addition, a cold front will cross the
Eastern Great Lakes region Saturday, with a secondary cold front
Saturday night that will bring a prolonged period of SCA conditions
to Lake Erie, and the far western and eastern sections of Lake
Ontario. A lighter southerly fetch of winds Friday will allow for
non-SCA conditions along the nearshore waters of central Lake
Ontario.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...Small Craft Advisory until 10 AM EST Sunday for LEZ040-041.
         Small Craft Advisory until 10 AM EST Friday for
         LOZ043-044.
         Small Craft Advisory until 4 AM EST Monday for LOZ042-045.

&&

$$

SYNOPSIS...CHURCH
NEAR TERM...CHURCH
SHORT TERM...TMA
LONG TERM...SMITH
AVIATION...CHURCH
MARINE...CHURCH/THOMAS


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