822
FXUS61 KBUF 201730
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
130 PM EDT Fri Sep 20 2024

.SYNOPSIS...
Little by little...our prolonged stretch of outstanding weather will
come to an end. A vigorous mid level disturbance will dive across
the region on Saturday to generate some showers and thunderstorms
over the western counties...then after a fine day on Sunday...a wavy
frontal boundary will set up over our area to support scattered
showers and potentially some thunderstorms through much of the
upcoming week. The change to unsettled weather will be accompanied
by cooler...more seasonable conditions.

&&

.NEAR TERM /THROUGH SATURDAY NIGHT/...
Fantastic weather will be found throughout the region through this
evening...as high pressure extending from the Canadian maritimes to
the Lower Great Lakes will maintain sun filled skies with July like
temperatures. Highs will be similar to that of the past week with
readings generally topping out in the lower 80s for most areas and
the mid to upper 70s for higher terrain and the immediate
lakeshores.

Persistent high pressure arching from eastern Quebec to the Lower
Great Lakes will remain in place tonight to assure us of more fair
dry weather...but high clouds will return ahead of a vigorous mid
level disturbance that will approach from the Upper Mississippi
valley. The increased cloud cover will portend more unsettled
weather for the start of the weekend...at least across the western
counties. Otherwise it will be mild tonight with the mercury only
dropping off into the mid 50s (Srn Tier/Lewis county) to lower 60s
(most elsewhere).

A vigorous shortwave...seen in WV imagery crossing the upper-most
portion of the Mississippi valley this afternoon...will make its way
across the Upper Great Lakes tonight before diving southeastward
across our western counties on Saturday. Fairly strong low level
convergence with the passing of this feature will be accompanied by
some added lift from a 100kt jet to our west...and this will result
in showers and possible thunderstorms over the western counties...
mainly during the afternoon. A tenth to a quarter inch of rain is
forecast for this area...while increased cloud cover but mainly dry
conditions will be found east of Lake Ontario. It will remain warm
though...as max temps will range from 75 to 80.

The aforementioned shortwave will exit across Pennsylvania Saturday
night...stripping away the mid level moisture and taking the
associated shower activity with it in the process. Meanwhile...mid
level ridging will quickly build in from the Upper Great Lakes. This
will aid in at least partially clearing the skies with the most
stubborn cloud cover expected to be over the Finger Lakes region.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
After the mid-level shortwave trough passage on Saturday, a brief
ridge will slide across the lower Great Lakes Sunday. At the surface
this will support surface high pressure over the Canadian maritimes
to extend southwestward across the Northeast and into the lower
Great Lakes. This will support one last day of dry weather across
western and northcentral New York Sunday.

The mid-level pattern will then shift Monday initiating a period of
active weather. This being said, surface low pressure will lift
northeast across the central Great Lakes, dragging a cold front
across the area Monday and Monday night. Starting late Sunday night,
the first of the showers will move into far Western New York. Then
as the cold front sweeps across the area, showers and thunderstorms
will gradually move from west to east across the area.

&&

.LONG TERM /TUESDAY 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 /18Z FRIDAY THROUGH WEDNESDAY/...
VFR conditions with light winds will remain in place through tonight.

While cigs will drop to less than 10kft over the western counties
Saturday morning...VFR conditions will persist. The lowering cigs
will be accompanied by scattered showers.

Outlook...

Saturday night...Mainly VFR weather with showers over the western
counties ending. MVFR to IFR cigs developing across the Srn Tier.
Sunday...Mainly VFR.
Monday through Wednesday...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...RSH
NEAR TERM...RSH
SHORT TERM...EAJ
LONG TERM...Thomas
AVIATION...RSH
MARINE...Hitchcock