975
FXUS61 KBUF 270203
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
1003 PM EDT Sun May 26 2024

.SYNOPSIS...
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 /UNTIL 6 PM MONDAY EVENING/...
A warm front entering far western NY late this evening will
weaken as it moves across the area through about 4 a.m. Can`t
rule out a few storms with gusty winds for the next couple
hours, but the risk is low since most mesoscale guidance weakens
this line overnight. It will bring at least some rain to most
locations, and with PWAT values increasing to around 1.5" it
could produce brief heavy downpours even if flood potential is
limited due to storm motion.

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 (particularly the 00Z HRRR),
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, but would
not be surprised to see the Eastern Lake Ontario region to be
upgraded to a slight risk.

In addition, heavy rain is also a concern. Given the
environment with PWATS in the 1.5 inch 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 with 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 /6 PM MONDAY EVENING 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 SATURDAY/...
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 /02Z MONDAY THROUGH FRIDAY/...
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.
Storms may produce brief periods of MVFR or lower.

Also, winds aloft will increase but the stronger winds will be a
bit above 2k feet. This will result in wind shear but it appears
slightly too high to include LLWS in the TAFS.

Another line of thunderstorms will move through with the leading
edge of a shortwave and a pre-frontal trough. This line will
move across Western NY during the morning hours, reaching the
eastern Lake Ontario region in the afternoon. Strong winds aloft
may support some strong to severe storms with gusty winds. There
also will be lots of low moisture ahead of this trough, with
MVFR cigs likely. Following the trough, winds will pick up at
KBUF and KIAG, but these winds will help suppress afternoon
convection at these terminals.

Outlook...

Monday night...VFR/MVFR. Showers and thunderstorms likely.

Tuesday and Wednesday...Restrictions possible with showers.

Thursday and Friday...VFR.

&&

.MARINE...
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 small
craft headlines likely to be needed during this time period.
This also could require beach hazards statements for dangerous
swimming conditions.

Strong to severe thunderstorms with gusty winds possible
Monday.

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/Apffel
MARINE...AR/Apffel