Altmar, New York Weather Forecast Discussion

184
FXUS61 KBUF 222249
AFDBUF
Area Forecast Discussion
National Weather Service Buffalo NY
649 PM EDT Mon Sep 22 2025
.SYNOPSIS...
A slow moving trough of low pressure will bring beneficial rain to
the region through midweek, with several rounds of showers and
scattered thunderstorms. Another low pressure system will move into
the Great Lakes late in the week, with additional rain chances in an
unsettled pattern.
&&
.NEAR TERM /THROUGH TUESDAY/...
Deep moisture and the passage of several low amplitude shortwaves
will continue to support a few waves of showers and isolated to
widely scattered thunder moving from southwest to northeast across
the region tonight. One such area of rain will move across the
Southern Tier and western Finger Lakes this evening, with another to
follow overnight through early Tuesday morning. In general, the most
widespread rain and greatest rainfall amounts will be found across
the Southern Tier and western Finger Lakes, with much lower amounts
close to the Canadian border.
Unsettled weather will continue Tuesday as additional shortwave
energy works through the region and an associated weak wave of low
pressure moves through the forecast area. Expect scattered to
numerous showers and storms around much of the day. The greatest
coverage of showers and storms will once again be across the
Southern Tier, Finger Lakes, and inland areas east of Lake Ontario,
with stable lake shadows lowering the rain chance and rainfall
amounts east of the lakes. Marginal instability and limited shear
should limit severe threat. Outside of the showers and storms it
will be humid with highs in the 70s.
&&
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
During Tuesday the axis of an elongated...positively-tilted upper
level trough will gradually slip southeastward from the Upper Great
Lakes/central Quebec...with the eastern and western portions of this
trough then gradually separating Tuesday night and Wednesday. As
these separate...the eastern portion will eject east across the
Canadian Maritimes...while the western portion merges with
additional shortwave energy making its way eastward from the Plains
states...leading to the development of a rather broad cutoff low
somewhere between the Mississippi Valley and Upper Great Lakes.
Before this separation occurs...the gradual southeastward
advancement of the upper trough axis will encourage an associated
weak surface cold front and wave of low pressure to push across our
area during the course of Tuesday. In the process...these features
will interact with a rather moist (PWATs of 1.50-1.75") antecedent
airmass and developing modest amounts of diurnally-driven
instability...leading to numerous showers and scattered storms
across interior portions of the CWA... particularly as the front
pushes south during the late morning and afternoon. Further north
and west...convective coverage should be notably lower back closer
to/over Lakes Erie and Ontario as per the shorter-term/higher-
resolution guidance...and as such have cut back on the far-too-
broadbrush likely/categorical PoPs advertised by blended guidance in
these areas.
During Tuesday night convective coverage will wane with the loss of
heating and as the weak cold front/surface wave and deeper moisture
depart to our south and east...and as surface-based ridging edges
southward from Quebec. This should lead to a drier period for later
Tuesday night and Wednesday...though still cannot rule out a few
isolated to widely scattered showers as the lingering troughing
aloft slowly gives way to the developing closed low to our south and
west.
After that time...there is loose agreement amongst the guidance that
the cutoff low to our west will tend to open up and slowly push
eastward across the Upper Great Lakes and Ohio Valley through the
balance of this period...though there remains a considerable amount
of variance on the details of all this. At the surface...this should
result in some semblance of an attendant surface wave lifting
northward and near/across our region...with this and an attendant
increase in Gulf-based moisture leading to another uptick in shower
potential through Thursday/Thursday night.
While temperatures during this period will generally be cooler than
those of the preceding couple of days...these will still average out
above normal...with readings running roughly 5 degrees above normal
each day...and some 5-10 degrees above normal each night.
&&
.LONG TERM /FRIDAY THROUGH MONDAY/...
The unsettled weather continues early in the period as the mid
level trough slides across the region. Moist southerly flow
maintained ahead of the trough should continue the showery
pattern on Friday. Main trough axis will shift east by the
weekend with an overall trend toward drier weather as a surface
ridge builds in later in the weekend and into early next week.
&&
.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
Deep moisture and the passage of several low amplitude upper level
shortwaves will continue to support numerous rounds of showers and a
few embedded thunderstorms tonight through Tuesday, with individual
waves of rain difficult to time and place. In general, the greatest
coverage and frequency of rainfall will be found across the Southern
Tier and western Finger Lakes, with lower rain chances close to the
Canadian border. Any of the heavier showers will produce local VSBY
restrictions. Thunder coverage will remain fairly sparse, with most
of the limited thunder this evening and again Tuesday afternoon.
CIGS will generally run VFR this evening except in any heavier
showers. Overnight, MVFR/IFR CIGS will become more widespread across
the higher terrain of the Southern Tier and western Finger Lakes.
Tuesday, expect widespread MVFR CIGS to expand to lower elevations,
with some IFR continuing across higher terrain.
Outlook...
Wednesday...VFR/MVFR with scattered showers and isolated
thunderstorms.
Thursday...MVFR/IFR with showers likely and a chance of
thunderstorms.
Friday...VFR/MVFR with scattered showers.
Saturday...Mainly VFR.
&&
.MARINE...
Southerly component winds will continue to decrease into this evening,
with light winds expected tonight. Light winds and calm waters
continue Tuesday and Tuesday night. A northeast wind will create
a moderate chop on the waters starting Wednesday.
&&
.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...None.
&&
$$
SYNOPSIS...Hitchcock/TMA
NEAR TERM...Hitchcock/TMA
SHORT TERM...JJR
LONG TERM...TMA
AVIATION...Hitchcock
MARINE...HSK/TMA

NWS BUF Office Area Forecast Discussion