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540
FXUS61 KBUF 191044
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
644 AM EDT Mon May 19 2025

.SYNOPSIS...
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Canadian high pressure over the region will result in cool, dry
weather through Tuesday. Clearing skies will likely result in
areas of frost tonight, particularly across wind sheltered areas
east of Lake Erie. A closed low pressure system will then bring
unsettled weather and more unseasonably cool temperatures
Wednesday through Saturday.
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&&

.NEAR TERM /THROUGH TONIGHT/...
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A closed low will churn over the southern Canadian Maritimes through
the day today, then pivot southeast into the Atlantic tonight. Cool
northerly flow on the backside of this system will result in
early clouds and patchy drizzle (S. Tier). Otherwise it`ll be
another day with temperatures largely in the 50s, though a wedge
of Canadian high pressure extending southward from Hudson Bay
will at least finally erode away the cloud cover across Western
NY by this afternoon.

While the clearing will result in some welcomed sunshine later today,
after dusk it will combine with light winds and min temps in
the 30s to pose a risk of frost development. Confidence in this
occurring is highest across the Southern Tier, especially in the
wind sheltered areas which may see widespread frost. Further
north across the lower terrain areas frost coverage should be
lower, with patchy coverage at best across the counties
bordering the southern Lake Ontario shoreline. Overall lower
confidence east of Lake Ontario where a lingering gradient wind
and cloud cover could preclude frost development entirely.
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&&

.SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
Retreating surface high pressure Tuesday...this between a low
pressure system off the Atlantic coastline and an incoming mid level
low/surface low over the midwest. This will bring a sunny start to
the day, but increasing clouds through the afternoon with the loss
of mid level subsidence. This may very well prove to be the start of
a lengthy period of cloud cover for our region, so enjoy the
sunshine for Tuesday.

As the low pressure system to the west and its associated warm front
draws closer to the Great Lakes region ongoing convection over the
eastern Corn Belt States will attempt to push into our region. There
continues to be model disagreement to the arrival timing of
convective activity Tuesday night as instability will generally
linger well to our west, which is where most of the convective
shower activity will likely be concentrated. A few rain showers will
become likely later in the night across SW NYS as upstream
convection advances farther eastward.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
A slow moving, moisture rich, cool, vertically stacked low through
the lower and mid atmosphere will bring an extended period of
unsettled weather with on again/ off again rain showers through
this period.

There may be some improvement for Sunday with less duration/coverage
area of showers as the low moves off the New England coastline, but
moist cyclonic flow will maintain cool conditions with still chances
for showers.

&&

.AVIATION /12Z MONDAY THROUGH FRIDAY/...
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A closed low pressure system will remain over the southern Canadian
Maritimes today. Cyclonic NW flow and residual low level moisture on
the backside of this system will result in a wealth of patchy
stratocu with variable bases through at least the first half of the
morning. Patchy drizzle in the Southern Tier should taper off after
12z.

Conditions will improve to mainly VFR generally from north to south
across Western NY as clouds scour out late morning into the early
afternoon. Confidence is lower in the timing and amount of clearing
that will occur east of Lake Ontario in closer proximity to the
lingering area of low pressure. OVC/BKN cigs will likely prevail at
KART through this afternoon, then SCT/FEW tonight.

Outlook...

Tuesday...Mainly VFR.
Wednesday and Friday...IFR to MVFR with showers.
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&&

.MARINE...
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A light to modest chop at times along the the southern half of Lake
Ontario as a north to northwest wind persists on the backside of a
low pressure system over the Canadian Maritimes. Surface high
pressure building southward from northern Canada should keep winds
light enough to preclude SCA conditions on the lakes through Tuesday.

A low pressure system moving into the eastern Great Lakes from the
Ohio Valley Wednesday will then very slowly cross the lakes through
Friday. This will cause northeast winds to strengthen starting
Tuesday night. The greatest wave action is expected to remain mostly
offshore through Wednesday night, though SCA conditions could be
reached for a time along the southwestern shoreline of Lake Ontario.
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&&

.BUF WATCHES/WARNINGS/ADVISORIES...
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NY...Frost Advisory from 2 AM to 8 AM EDT Tuesday for NYZ010>014-
     019>021-085.
MARINE...None.
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&&

$$

SYNOPSIS...PP
NEAR TERM...PP
SHORT TERM...Thomas
LONG TERM...Thomas
AVIATION...PP
MARINE...PP