742
FXUS61 KBUF 211825
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
225 PM EDT Sat Sep 21 2024

.SYNOPSIS...
An upper level disturbance will cross the area, producing
scattered showers and a few isolated thunderstorms, mainly
through this evening across Western New York, the Genesee
Valley, and Finger Lakes. A narrow ridge of high pressure will
then bring a return to dry weather Sunday. The weather will then
turn unsettled, as a cold front moves into the area Monday and
stalls out, with several areas of low pressure moving northeast
along it through the course of next week, with numerous rounds
of showers and a few thunderstorms.

&&

.NEAR TERM /THROUGH SUNDAY/...
A mid level shortwave within northwest flow aloft will cross the
eastern Great Lakes through this evening. Modest diurnal instability
has developed this afternoon with surface-based CAPES nearing 1500
J/Kg. This combined with the forcing from the incoming shortwave
will produce an increasing coverage of showers and a few
thunderstorms. HREF/HRRR suggesting the best coverage will be
across the Genesee Valley/western Finger Lakes and interior
Southern Tier through about 8 PM this evening. A few showers
may reach the eastern Lake Ontario region, but coverage here
should be much less.

The evening showers/storms will faded by mid to late evening
with loss of heating and exiting shortwave, with any remaining
spotty showers ending before daybreak Sunday morning. Some
clearing along with light winds overnight will promote areas of
fog, especially across the Southern Tier and western New York,
and in any areas which receive rainfall through this evening.

Any morning fog and low stratus will burn off by mid morning,
leaving a mix of sun and clouds for the rest of the day with dry
weather prevailing as a narrow ridge builds into the eastern Great
Lakes. Temperatures will remain above normal with most highs in the
mid 70s to around 80.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/...
A well defined closed low over the desert Southwest this early
morning will open up with a piece of energy transversing the Plains,
and phasing with a northern branch jet to bring enhanced synoptic
lift for the formation of showers late Sunday night and through
Monday. Deeper moisture will be near the surface low along a stalled
frontal boundary...with this low just to north of Lake Erie. This
will allow for rainfall amounts Monday and Monday night for most
areas to remain a third of an inch or less...with heavier rain just
to our west and north.

With this low remaining to our west, surface winds will generally
remain south to southeast, with the downslope regions near Lake
Erie/Thruway and along the southern Lake Ontario shoreline likely to
top the 70 degree mark Monday, while cloud cover over higher terrain
will keep the interior higher terrain of WNY and the Tug Hill in the
lower to mid 60s.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
Pattern this period will feature unsettled weather throughout. 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
Plains/Midwest region, which will linger unsettle weather through
the remainder of this period. Where this closure occurs is still
with great uncertainty among the models, increasing further the
uncertainty in the weather towards the end of this period.

Will carry chance to likely PoPs each day through this period.
Wettest period may end up being Tuesday night into Wednesday as a
stronger LLJ of 30 - 35 knots, and surface warm front moves across
the region. Marginal instability will allow for a risk of thunder
through Thursday, 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 SATURDAY THROUGH THURSDAY/...
A mid level shortwave will cross the region bringing with it a
period of cloudiness with VFR bases and scattered showers through
this evening. Most of the shower activity will be from western New
York to the Finger Lakes. Overall, coverage of the showers will stay
scattered to widely scattered, with the best chance of a more
organized cluster of showers across the Genesee Valley and Southern
Tier between 19z and 24z. There may be a few isolated
thunderstorms as well in this area. Given the expected scattered
nature of showers, and even more sparse coverage of thunder,
used VCSH in the TAFs for now.

Tonight, any remaining showers will taper off and end, and skies
will partially clear. The light winds and clearing skies will allow
areas of IFR fog and low stratus to develop, especially across the
Southern Tier and Finger Lakes valleys and in any locations that
receive rainfall today. KJHW is the most likely terminal to
experience fog and IFR overnight through Sunday morning.

Outlook...

Sunday...Patchy IFR fog and low stratus through mid morning, then
mainly VFR.
Monday through Thursday...VFR/MVFR with showers likely and a chance
of thunderstorms at times.

&&

.MARINE...
East to southeast winds will continue through the weekend on the
lower Great Lakes, directing most of the moderate chop into the
middle of the lakes and Canadian waters.

Low pressure and a cold front will approach from the west late
Sunday night and Monday, with increasing south to southeast winds on
both lakes. This wind direction will once again keep the greater
wave action well offshore and in Canadian waters.

&&

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

&&

$$

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