031
FXUS61 KBUF 200736
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
336 AM EDT Fri Sep 20 2024

.SYNOPSIS...
High pressure will remain centered over Quebec through tonight, with
a ridge extending back towards the eastern Great Lakes providing
another day of dry and warm weather. A mid level disturbance will
then cross the area Saturday through early Sunday morning, bringing
showers and a few thunderstorms with uneven coverage of rain. A
narrow ridge of high pressure will bring a brief return to dry
weather for much of Sunday and Sunday night. A slow moving area of
low pressure will then bring several days of rain showers starting
Monday and lasting much of next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
IR satellite imagery and surface observations showing clear skies
across the region early this morning, with areas of fog developing
from the Southern Tier river valleys east across the Finger Lakes to
areas southeast of Lake Ontario. The fog will continue through mid
morning before burning off.

Surface high pressure centered over eastern Quebec will remain in
place today, with a weaker ridge surface and aloft extending back
across the eastern Great Lakes. This will provide another dry and
warm day with mostly sunny skies outside of some modest increase in
high clouds from west to east, and a few diurnal cumulus along and
inland of the lake breeze boundaries. Highs will be similar to
yesterday, with lower 80s for the lower elevations and mid to upper
70s for higher terrain and the immediate lakeshores.

Tonight, weak surface high pressure will remain in place across the
eastern Great Lakes. A mid level trough over the upper Great Lakes
will advance ESE overnight, with height falls and DPVA starting to
spread into southern Ontario just upstream of Western NY. This will
bring an increasing and lowering mid level cloud deck overnight, but
showers should remain west of the area until around or just after
daybreak Saturday. The increase in clouds and an uptick in southerly
flow should keep fog formation to a minimum.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
Saturday, a mid level shortwave will move from northern Lake Huron
in the morning southeast across the eastern Great Lakes by afternoon
and evening, spreading DPVA and height falls into our region.
Meanwhile, an ill-defined baroclinic zone stretching from just west
of James Bay to the eastern Great Lakes will tighten and become
better defined through the day in response to weak easterly flow and
cold advection over Quebec and eastern NY, and warm advection over
the central Great Lakes. The combination of forcing from the mid
level shortwave and the frontal zone combined with adequate moisture
and weak diurnal instability will support the likelihood of showers
and a few thunderstorms Saturday.

The first of the showers may already be moving into far Western NY
by around daybreak Saturday, but overall the best coverage of
showers and a few thunderstorms will be Saturday afternoon through
early to mid evening across Western NY, the Genesee Valley, and
western Finger Lakes. A few of the embedded thunderstorms may
contain moderate downpours in the afternoon and evening, but expect
the coverage of rainfall to be very uneven. The North Country should
stay mainly dry in closer proximity to drier air and subsidence
associated with high pressure over eastern Quebec.

Saturday night, the mid level shortwave will move southeast across
NY/PA, reaching the Mid Atlantic states by Sunday morning. Still
expect good coverage of showers and a few thunderstorms early in the
evening, especially across the Genesee Valley and western Finger
Lakes. The coverage of showers will gradually decrease overnight,
with the last of the showers over the Genesee Valley and Finger
Lakes ending around or shortly before daybreak Sunday.

Sunday, once the last of the showers exit early in the morning,
expect mainly dry weather for the rest of the day with a mix of sun
and clouds. Sunday night will start dry, then clouds will increase
from west to east overnight ahead of a more substantial mid level
trough digging into the upper Midwest. Height falls and an
associated cold front will move through the central Great Lakes
overnight, and the first of the showers with this system may reach
Western NY by late Sunday night. More on this system in the long
term section below.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
A pattern change this period will return unsettled weather to the
Eastern Great Lakes. Aloft a 250/300 hPa southern branch of the jet
stream will lift northward towards the Ohio Valley, while a northern
branch jet within a developing long wave trough will be dropping
over the Prairies of Canada and into the Northern Plains. In an
amplifying pattern, these jets will help to close the upper level
trough over the Great Lakes region, which will linger unsettle
weather through the remainder of this period.

Initially through Wednesday several shortwave troughs within the
southern branch of the jet will be driving our weather, but by
Wednesday night and into Thursday the northern jet will become more
of a factor.

Will carry chance to likely PoPs each day through this period.
Marginal instability will allow for a risk of thunder, though none
of the days is overly convincing for thunder chances.

Cloud cover and showers will keep daytime highs close to normal,
while these same clouds will hold overnight lows above normal
through the period.

&&

.AVIATION /08Z FRIDAY THROUGH TUESDAY/...
Clear skies and light winds will promote an expansion of fog through
the early morning hours, with areas of MVFR/IFR. The fog will be
most prevalent from the river valleys of the Southern Tier through
the Finger Lakes to points southeast of Lake Ontario. KJHW, KART,
and KROC all may see a few hours of IFR in fog around daybreak,
although confidence is not particularly high for any of those
airfields.

The fog will burn off by 14Z, leaving VFR to prevail for the rest of
the day with just a modest increase in high clouds from west to
east, and a few diurnal cumulus along and inland of the lake breeze
boundaries. Dry weather and VFR will continue to prevail tonight
with mid level clouds increasing and lowering from west to east. The
increase in clouds and increasing southerly winds should keep fog
formation to a minimum.

Outlook...

Saturday...VFR/MVFR with showers likely and a chance of
thunderstorms, especially across Western NY.
Sunday...VFR, except for patchy early morning fog with local IFR
across the Southern Tier and east of Lake Ontario.
Monday and Tuesday...VFR/MVFR with showers likely and a chance
of thunderstorms.

&&

.MARINE...
High pressure will remain over eastern Quebec and the Canadian
Maritimes through the weekend. The pressure gradient to the west of
this high will start to increase east to northeast winds on Lake
Ontario today with a light chop, and moreso over the weekend with a
moderate chop developing. Winds will generally be lighter on Lake
Erie through the weekend.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...None.

&&

$$

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