661
FXUS61 KBUF 241815
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
215 PM EDT Tue Sep 24 2024

.SYNOPSIS...
Low pressure will move across the Great Lakes tonight,
spreading another round of rain across the region. A trailing
front will move slowly across the area Wednesday through
Wednesday night and support some additional rainfall. A few
showers may linger Thursday, especially east of Lake Ontario.
High pressure will then build into the Great Lakes region,
bringing a return to mainly dry weather Friday through the
weekend.

&&

.NEAR TERM /THROUGH WEDNESDAY NIGHT/...
A deep longwave trough will dig across the Great Lakes and Ohio
Valley through Wednesday. Large scale forcing for ascent will
increase ahead of this trough through tonight. This lift will
be supported by DPVA, topped by mid/upper level diffluent flow,
and deep moisture transported northward by a 40 knot southerly
low level jet. As a result steady showers will continue to spread
from west to east across Western NY through this evening.
Terrain influences will play an important role in coverage of
rain and also rainfall amounts. Persistent south/southeast
downslope flow will result in shadows of lower rainfall amounts
and diminished rain coverage to the north of terrain and on the
lake plains. For these areas rainfall totals will average a
tenth to a quarter inch, with the greatest rainfall amounts east
of Lake Ontario where around a half inch of rain is expected.

Southerly downslope winds will continue Wednesday, and the lake
plains may see a period of completely dry weather Wednesday
morning due to a mid level dry slot and the drying influence of
downslope flow. However, the frontal zone will remain draped
from the Ohio Valley to Central NY, and this along with diurnal
heating/instability will support an uptick in showers Wednesday
afternoon.

While there will not be much surface based instability during
this event, there will be elevated instability which could
support some thunderstorms embedded in heavier showers this
afternoon through Wednesday evening.

The surface low will track to our north and into southern Quebec
Wednesday night, with a trailing cold front moving across our
region. This will bring another round of showers to the area,
especially east of Lake Ontario which will be closer to the
upper level trough. This will bring another half inch or so of
rainfall to that region.

During this time temperatures will average above normal,
especially overnight lows. The lake plains will be the warmest
locations due to warming from the southerly flow downsloping.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY/...
Dry air filters into the region Thursday as the mid-level
trough axis moves east of the forecast area. The strong ridge
will move into the Great Lakes region while the potential
tropical storm moves into the southeast U.S. through Thursday
night. A strong southeasterly jet will transport moisture into
the Mid-Atlantic region and central Appalachians, however the
strong ridge will suppress moisture south of the forecast area.
By Friday, the remnants of any tropical storm will move
northward while high pressure extends into the forecast area
from Quebec. Dry weather will continue across the forecast area.


Temperatures will be slightly above normal with highs in the low to
mid 70s Thursday and Friday and lows in the 50s Thursday night.

&&

.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
The evolution of the upper low over the Mississippi Valley will be
the large scale feature to watch during this period. Ensemble
systems show a ridge across the Great Lakes region which should keep
the forecast mostly dry, however there are some signals from the
ensemble systems that draw the upper low further north and/or open
the low into a trough across the forecast area. This could result in
increasing moisture and therefore there are low chances of showers
across the forecast area through the weekend and into Monday.

Temperatures remain above normal through the period.

&&

.AVIATION /17Z TUESDAY THROUGH SATURDAY/...
An upper level trough will slowly dig across the Great Lakes
through Wednesday. A round of steady rain showers with a few
embedded thunderstorms will move from west to east across the
area through tonight. Rain will be moderate at times, reducing
vsby to MVFR. Cigs will vary, with southerly downslope flow
helping to keep the lake plains mainly VFR/MVFR despite the
rain. This includes KBUF/KIAG/KROC/KART. Mainly IFR cigs at
KJHW, with fog possible tonight.

Expect a break in the showers for most locations Wednesday
morning as a LLJ exits to the east. However, showers and a few
thunderstorms will expand in coverage Wednesday afternoon due to
diurnal heating, especially from the Genesee River valley
eastward.

Outlook...

Wednesday night...MVFR/IFR with showers likely. A few widely
scattered thunderstorms possible.

Thursday...MVFR east of Lake Ontario with a chance of showers.
Becoming mainly VFR elsewhere.

Friday through Sunday...Mainly VFR. Local IFR in valley fog
across the Southern Tier possible overnight into the morning.

&&

.MARINE...
A moderate pressure gradient will remain in place over the eastern
Great Lakes through Wednesday between persistent high pressure over
the Canadian Maritimes and low pressure moving through the central
Great Lakes. This will maintain moderate southeasterly flow through
Wednesday, with the strongest winds on the east half of Lake
Ontario tonight through the first half of Wednesday. The
southeast wind direction will continue to push the greater wave
action into Canadian waters, but the offshore winds will become
strong enough to require a Small Craft advisory for the eastern
ends of Lake Ontario and Lake Erie.

Winds will gradually become southwest and then west Wednesday night
through Thursday as a trough crosses the eastern Great Lakes from
west to east, with wind speeds decreasing with the passage of the
trough. Northeast flow will then pick up Friday, possibly
requiring small craft headlines on Lake Erie and western Lake
Ontario.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...Small Craft Advisory from 7 PM this evening to 8 AM EDT
         Wednesday for LEZ040-041.
         Small Craft Advisory from 10 PM this evening to 2 AM
         EDT Thursday for LOZ045.

&&

$$

SYNOPSIS...Apffel/Hitchcock
NEAR TERM...Apffel/Hitchcock
SHORT TERM...HSK
LONG TERM...HSK
AVIATION...Apffel
MARINE...Apffel/Hitchcock