203
FXUS61 KBUF 262242
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
642 PM EDT Sun May 26 2024

.SYNOPSIS...
Weak high pressure begins to depart off towards New England this
evening. A low pressure system tracking through the Great Lakes
region will bring increasing chances for showers and thunderstorms
tonight into Memorial Day as a pair of fronts push through our
region. Some of the stronger storms will have the potential to
produce torrential downpours and also gusty winds. Showers and some
thunderstorms will continue to be possible through midweek but drier
weather then return for the tail end of the week.

&&

.NEAR TERM /THROUGH MONDAY NIGHT/...
The fair weather will come to an end tonight, as a potent
shortwave nears the Great Lakes. A warm front tied to this
system will reach far Western NY around 9 or 10 p.m. and will
move across the area through around 4 a.m. HRRR and most other
high-res guidance weaken this convection as it becomes more
stable overnight, but can`t rule out a few storms with gusty
winds as it enters Chautauqua County late this evening. Chances
for severe winds diminish later tonight, but it likely will
bring showers and a few storms to most areas from the Genesee
River valley west. In addition, PWAT values increasing to around
1.5" will support some heavy downpours, although storms will be
moving which will limit the flood potential for tonight.

Memorial Day...a deepening low pressure system over Michigan looks
like it will bring a couple of rounds of widespread showers.
The primary forcing mechanism appears to be PVA associated with
the approaching mid-level trough and a pre- frontal trough.
While mid lapse rates are NOT forecast to be very impressive
(mainly ~7 deg c/km), there will be a lot of wind shear with
this trough with 850mb winds reaching around 50 knots and some
directional shear. The primary severe weather threat is strong
winds which could be transported to the surface within stronger
convection. The main forecast challenge will be determining when
and where there will be ample sunshine to destabilize the
atmosphere. In general it will be a mostly cloudy day, but
breaks of sun are possible and it will not take much sun to
produce ample instability to cause thunderstorms. Following
mesoscale guidance, perhaps there is a slightly greater risk for
severe weather east of Lake Ontario, where the shortwave trough
will move through during the afternoon hours. Given the wind
shear in place, cannot rule out an isolated tornado IF there
ample sunshine. However, without destabilization from breaks of sunshine,
this simply could turn out to be a non-event. SPC has the
entire forecast area in a marginal risk for severe weather.

In addition, heavy rain is also a concern. Given the
environment with PWATS still in the 1.5 range and short MBE
vectors...there will be an elevated risk for torrential
downpours and localized flooding concerns. This could
materialize if storms train across the same areas, especially if
this happens in areas which steep terrain or urban areas.

Monday night...broad area of low pressure to our northwest will
slowly track NNE into and across Quebec overnight. As the low
departs...showers and storms coverage will decrease with the passage
of the cold front. Although...we still can`t rule out a few
lingering showers overnight. Overall...much of the region will
see drier weather as the dry slot works through the Lower Lakes.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
The upper level pattern will feature a trough over the Great Lakes
region Tuesday through Wednesday night. There will be a series of
shortwave troughs that will rotate cyclonically and keep unsettled
and cooler conditions across western and north central NY.

The first shortwave trough and associated surface reflection will
move north of the forecast area Tuesday. A southwest flow will
increase through the day with breezy conditions northeast of Lake
Erie and east of Lake Ontario by afternoon. At 850mb, winds will be
near 40kts with temperatures around +5C. Cool air aloft during
daytime heating will create instability across the region. Showers
will increase in coverage through the daytime hours with a
convergence zone possibly forming from the Niagara Frontier to the
Syracuse region. An isolated thunderstorm can`t be ruled out.
Showers will quickly diminish in coverage Tuesday evening.

The next shortwave trough will sharpen as it approaches the region
from the north Tuesday night. A cold front will move into the Saint
Lawrence Valley by Wednesday morning. The chance for showers will
increase from north to south across the region Wednesday. Showers
will increase in coverage across the region Wednesday afternoon with
a low chance of thunderstorms. Ridging builds into the region
Wednesday night and mostly dry weather is expected overnight.

Notably cooler conditions will begin on Wednesday with daytime highs
in the mid 60s, upper 50s across the higher terrain.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
A relatively quiet stretch of weather expected as we close out the
month of May and move into June this period, with mainly dry weather
and a gentle day to day warming trend.

To open the period Thursday, the region will be situated under a
broad, positively tilted upper level trough centered over the
Canadian Maritimes. To the west, a strong, progressive ridge of high
pressure will be building eastward over the Great Lakes region. The
surface high from this feature will "undercut" the initial upper
level troughing to a degree, supporting fair albeit cooler than
normal weather for Thursday. Long range guidance is indicating an
uptick in moisture aloft as the trough axis pivots southward across
the eastern Great Lakes later Thursday or Thursday evening, with
some even producing some spotty light QPF as it moves through. Have
bumped up cloud cover by a small amount, but otherwise at this
juncture have stayed close to NBM output which places just sChc PoPs
across portions of the North Country Thursday afternoon.

The ridge of high pressure will begin to shrink as it quickly moves
across the Great Lakes and towards the East Coast Friday through
Saturday. On its heels will be a large troughing system over south-
central Canada and the Northern Plains. A robust shortwave rotating
through the base of this trough will move into the Midwest and into
the western Great Lakes in the back half of the weekend, which will
cause increased chances for showers and possibly thunderstorms
across our area late Saturday night through Sunday.

In regards to temperatures...Still under the influence of the upper
trough, temps Thursday and Thursday night will likely run some 5-10
degrees below normal with highs in the low to mid 60s and lows
ranging in the 40s. By the weekend however, temps should warm to
near or slight above normal with highs ranging in the 70s and lows
in the 50s.

&&

.AVIATION /22Z SUNDAY THROUGH FRIDAY/...
VFR flight conditions will be maintain across all terminals into
this evening.

Tonight...a warm front will approach the eastern Great Lakes
bringing showers with some embedded rumbles of thunder to our far
western terminals. Expect lowering Cigs overnight with low end VFR
to MVFR conditions area terminals.

While the potential is low (low confidence)...low level wind shear
will be possible over the western counties after 06z.

Outlook...

Monday...Restrictions likely with showers and thunderstorms.
Tuesday and Wednesday...Restrictions possible with showers.
Thursday and Friday...VFR.

&&

.MARINE...
Light wind and wave action will persist into this evening on area
lakes.

A warm front nears the Lower Lakes tonight with increasing chances
for showers and storms overnight. While winds are still expected to
remain light...gusty winds and higher wave action will be possible
with any of the showers and storms.

Wind flow picks up on Monday and remains elevated through Tuesday.
Winds could nudge into the 15 to 25 knots range with possible small
craft headlines needed during this time period. Scattered gusty
thunderstorms will also be possible Monday.

Boaters should continue to monitor the forecast, especially given
the holiday weekend which will likely increase boating activity.
This will especially be the case on Monday as conditions on the
lower Great Lakes will likely deteriorate.

Lighter winds and wave action return Wednesday through the rest of
the week.

&&

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

&&

$$

SYNOPSIS...AR
NEAR TERM...AR/Apffel/RSH
SHORT TERM...HSK
LONG TERM...PP
AVIATION...AR
MARINE...AR