158
FXUS61 KBUF 270439
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
1239 AM EDT Mon May 27 2024

.SYNOPSIS...
While the VAST majority of Memorial Day will be rain free...a
relatively deep storm system moving out of Lower Michigan will push
a pair of frontal systems through our area that will result in
several rounds of showers and drenching thunderstorms.
Unfortunately...unsettled weather will persist through mid week
while it will become progressively cooler.

&&

.NEAR TERM /UNTIL 6 PM MONDAY EVENING/...
A warm front pushing northeastward across our region overnight
will generate some showers...but with waning instability...the
coverage and intensity of this activity should continue to drop
off. Most areas will have trouble `measuring` any pcpn.

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 less
than 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 THIS 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 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 /06Z MONDAY THROUGH FRIDAY/...
While a warm front will push northeastward across the region
overnight...most areas will maintain VFR flight rules. There will be
MVFR cigs though across the western Southern Tier and the higher
terrain of the Finger Lakes region.

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.

An area of showers and thunderstorms is then forecast to push across
the far western counties during the morning hours with a few hours
of MVFR conditions possible within the activity. The showers and
storms will move to the Eastern Lake Ontario region for the
afternoon. Thunderstorms for that particular area will likely
include torrential downpours and possibly strong to damaging wind
gusts.

Speaking of which...more scattered convection will redevelop over
the western counties after 18z. This convection could also include
strong to severe weather...although the bulk of the time will
feature VFR weather.

Outlook...

Monday night...VFR/MVFR. Showers and thunderstorms likely.
Tuesday and Wednesday...Restrictions possible with showers.
Thursday and Friday...VFR.

&&

.MARINE...
While showers will move through the Lower Great Lakes overnight...
the risk for convection has greatly diminished. Otherwise moderate
easterlies will be in place for the bulk of the region.

Winds will freshen on Monday in the wake of a warm front and will
remain elevated through Tuesday in the wake of a cold front. 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...RSH
NEAR TERM...AR/Apffel/RSH
SHORT TERM...HSK
LONG TERM...PP
AVIATION...RSH
MARINE...AR/Apffel/RSH