335
FXUS61 KBUF 150521
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
121 AM EDT Thu May 15 2025

.SYNOPSIS...
Broad weak low pressure over the Ohio Valley and Mid-Atlantic
will gradually shift east before stalling along the Delmarva
Peninsula Thursday, resulting in a few showers through Thursday.
A few scattered thunderstorms will be possible Thursday
afternoon. An occluded front will lift northeast across the
region early Friday, supporting the continued chances for
showers and thunderstorms. Low pressure associated with the
occluded front will then reside across the Great Lakes through
the weekend supporting continued chances for showers. While this
all sounds pessimistic, should note that the rest of the week
and weekend will have periods of dry time.

&&

.NEAR TERM /THROUGH TODAY/...
An open negatively tilted trough across the Ohio Valley will drift
north across the Great Lakes and southern New England through
Thursday.

Minimal forcing and limited mid-level moisture will keep the area
mainly dry through tonight. However, due to a surface low entering
the Mid-Atlantic region, a few isolated showers are possible across
the western Southern Tier as the next area of moisture advects
northward late tonight.

The mid-level trough axis will lie overhead Thursday, sending a
plume of moisture and instability across the eastern Great Lakes.
The morning will start off mainly dry, with the exception of a few
showers to develop across the western Southern Tier. Diurnal
instability and low level forcing from lake breeze boundaries will
support an increase in shower activity Thursday afternoon. The best
coverage of showers will lie from the Southern Tier northeast across
the Genesee Valley to the western Finger Lakes, and across the
southern Tug Hill region. Weak flow and poor lapse rates will keep
the severe risk to a minimum through Thursday evening.

&&

.SHORT TERM /TONIGHT THROUGH SATURDAY/...
First upper low exits east across New England, making way for the
next stronger upper low to approach from the upper Midwest, making
it into the central Great Lakes by late Saturday.

Transient ridge crosses the area Thursday night in between these two
systems providing a brief period of dry time, before a potent
shortwave and associated surface trough push into western NY late
Thursday night, pushing across the remainder of the region through
the day Friday with a line of showers and storms along and ahead of
the boundary. While diurnal timing is not favorable for surface-
based convection, there will be plenty of elevated instability to
support/maintain thunderstorm activity. Couple this with 6 km bulk
shear values of 30-40 knots and there will be at least the limited
risk for a few severe storms across western NY late Thursday night
into early Friday morning, with strong gusty winds and some hail the
primary hazards. SPC continues with a Day 2 Marginal Risk across
this portion of our area to account for this. Line of showers and
storms will then continue to move east across the remainder of the
area through the day, however there is more uncertainty wit regard
to severe weather possibilities from the Finger Lakes east as better
shear is projected to move northeast of the area. This will
obviously need to be monitored going forward.

Upper level and associated surface trough exit east late Friday,
with just some lingering widely scattered showers/rumble of thunder
through the first half of Friday night, but also some dry time built
in as well. This will once again be short-lived as a pair of cold
front moves are set to cross the region second half of Friday night
through the day Saturday, bringing a couple more rounds of organized
showers and storms into western and north-central NY. Low confidence
in severe potential at this point, however steepening lapse rates
aloft coupled with bulk shear values once again around 30-40 knots
could support a few stronger storms.

It will be somewhat humid during this time period, with temperatures
remaining above average.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
This period will feature much cooler and showery weather for the
second half of the weekend as a stacked area of low pressure and
broad surface wave move across the area Saturday night, then exit
east into New England Sunday. General troughing will linger across
the Northeast well into next week, with strong CAA around the system
bringing below normal temperatures for much of the period, before
returning to near normal levels by mid week.

Medium range guidance then diverges with just how fast our area
dries out next week, especially eastern half the area as some
projections show the upper low stalling out over New England, while
other guidance shunt it eastward allowing a large area of high
pressure to build in quicker, with dry conditions for the entire
area by the start of the new work week. That said, do expect all but
the eastern Lake Ontario to dry out Monday/Tuesday, with again our
extreme eastern areas with some uncertainty as to when they will
completely dry out. Ridge will then move east as yet another area of
low pressure approaches, bringing rain chances back into the
forecast by mid week.

&&

.AVIATION /06Z THURSDAY THROUGH MONDAY/...
A broad negatively tilted trough will lift northward into the Great
Lakes overnight and into Thursday, then weaken and shift east of the
region later Thursday evening. A steady influx of moisture within
this trough will result in a wide range of cigs through at least
Thursday morning, though little in the way of forcing present to
induce much in the way of showers. VFR is expected to prevail across
the lower terrain areas (KBUF/KIAG/KROC) with low MVFR and spotty
IFR across the higher terrain areas and east of Lake Ontario. Lower
confidence in cigs at KJHW and KART.

Cigs are expected to improve through Thursday morning with mainly
VFR by the afternoon. Diurnal instability and lake breeze boundaries
will then cause the development of scattered showers and a few
thunderstorms with brief, localized MVFR restrictions into Thursday
evening.

Outlook...

Friday and Saturday...VFR/MVFR with showers likely and
afternoon/evening thunderstorms with local/brief restrictions.

Sunday...Mainly VFR with scattered showers.

Monday...Mainly VFR.

&&

.MARINE...
Diminishing easterlies on Lake Ontario will continue to produce a
light chop across the western half of the lake overnight. Otherwise,
relatively light wind and wave action is expected through Thursday
night.

Winds will become south/southwesterly Friday through
Saturday and increase, with Small Craft Advisory conditions possible
by Saturday as a cold front crosses the eastern Great Lakes. Small
Craft Advisory conditions may continue through Sunday behind the
cold front with moderate westerlies.

&&

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

&&

$$

SYNOPSIS...EAJ/TMA
NEAR TERM...EAJ/TMA
SHORT TERM...JM
LONG TERM...JM
AVIATION...PP
MARINE...EAJ/Hitchcock/PP/TMA