-- Discussion containing changed information from previous version are highlighted. --
385
FXUS61 KBUF 221733
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
133 PM EDT Sun Sep 22 2024

.SYNOPSIS...
A cold front will near the region late tonight and Monday, bringing
showers and an isolated rumble of thunder, primarily Western New
York. As a warm front lifts across the region Tuesday night and
Wednesday, more widespread rain showers will fall upon the entire
region.

&&

.NEAR TERM /THROUGH MONDAY NIGHT/...
While this evening will start off rain-free throughout the region...
an approaching wavy frontal boundary will spread some showers across
the western counties after midnight. It will remain mild tonight
with mins ranging from the lower 60s in most areas...to near 50 in
the vcnty of the Tug Hill.

Monday, a mid level shortwave and associated surface trough will
move east across the eastern Great Lakes, weakening with time and
eastern extent. Showers will have spread into much of Western NY
from the Genesee Valley westward by daybreak Monday with the arrival
of deeper moisture and forcing. The showers will then spread east
through the day, reaching Central NY and the eastern Lake Ontario
region by afternoon. The coverage and intensity of showers will
likely diminish with eastern extent as forcing weakens. Meanwhile
across Western NY, expect some dry time to develop Monday afternoon
in the wake of this first trough as a mid level dry slot moves into
the area.

Monday night, the initial mid level and surface trough will continue
to weaken and wash out over Central NY and the eastern Lake Ontario
region as it moves into a persistent ridge and subsidence over the
northeast US. An area of mid level dry air will move into the
eastern Great Lakes, supporting a temporary lull in rain. Low level
moisture will persist, so a few isolated light showers cannot be
ruled out, but expect it to be rain free much of the time Monday
night.

&&

.SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
-- Changed Discussion --
Tuesday through Tuesday night, a northern stream trough will
dig into the Upper Midwest, carving out a deep longwave trough
over the upper Mississippi Valley and western Great Lakes. The
digging upstream trough and associated downstream flow
adjustments will force a southern stream shortwave and a
substantial area of deep moisture to move northeast from the
Ohio Valley into the eastern Great Lakes later Tuesday through
Tuesday night. Tuesday may start mainly dry in Western NY, but
rain chances will then increase through the day as deep moisture
and forcing increase with the approach of the southern stream
shortwave. Farther east, expect dry time to last longer through
the day Tuesday, with rain arriving in the eastern Lake Ontario
region later in the afternoon or evening. Rain will be
widespread Tuesday night as the best forcing and deepest
moisture cross the region. There could be some isolated thunder
later Tuesday through Tuesday night with limited instability,
but expect coverage to remain sparse.

Temperatures will trend downward through the first half of the week
with persistent clouds, showers, and a somewhat cooler airmass.
Highs Monday and Tuesday will be in the lower 70s for lower
elevations and 60s for higher terrain, but it will be cooler than
that during periods of rainfall.
-- End Changed Discussion --

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
A deep longwave trough over eastern North America on Wednesday will
advance slowly east to the eastern seaboard through the end of the
week. While this general large scale pattern is well agreed upon in
model and ensemble guidance, the smaller scale details have shown
considerable run to run differences, especially in the handling of a
potential closed low over the south central US late in the week.

For our area, the slow eastward progress of the longwave trough will
keep unsettled weather in the forecast with a good chance of rain
showers Wednesday through at least Thursday. The finer scale
synoptic details that are quite uncertain at this point will
determine how widespread the rain will be on these days. The rain
chances will gradually taper off from west to east Friday through
Saturday as the trough moves slowly east, and the plume of deeper
moisture moves to along, and eventually off the east coast.

Temperatures will continue to run cooler than the past few weeks.
Highs most days will be in the lower 70s for lower elevations and
60s for higher terrain, but it will be cooler than these values
during periods of rain.

&&

.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
While cigs will lower tonight with some showers developing over the
far western counties...VFR weather can be expected for most areas.
The exception will be across the western Southern Tier where cigs
may drop to 1500 ft by daybreak.

Cigs will continue to deteriorate during the day Monday...as a wavy
frontal boundary will become nearly stationary over the far western
counties. This feature will be accompanied by increasingly likely
showers and possible thunderstorms.

Outlook...

Tuesday...IFR to MVFR cigs over the western counties in scattered
showers and thunderstorms, but mainly VFR and dry east of Lake
Ontario.
Wednesday...IFR to lower end MVFR regionwide with the likelihood of
more showers and thunderstorms.
Thursday...MVFR with scattered showers...mainly east of Lake
Ontario.
Friday...VFR.

&&

.MARINE...
A weak ridge of high pressure will maintain light winds and low wave
heights on the Lakes today. There may be a little fog over the
western Lake Ontario waters through the morning and early afternoon
hours.

Tonight winds will become southeasterly ahead of a cold front. These
southeast winds will approach 20 knots over the offshore waters of
eastern Lake Ontario...with waves around four to five feet rolling
into the Canadian waters.

This cold front will stall just to the west of the Lower Great
Lakes, with a south to southeast flow maintained over the Lake
waters through Wednesday. Eventually this cold front will push
eastward, with winds veering to a westerly flow Wednesday night and
Thursday.

&&

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

&&

$$

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