217
FXUS63 KAPX 231757
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
157 PM EDT Sat Aug 23 2025

.KEY MESSAGES...

- Showery and cooler weather ahead

- Thunder today, and off and on through the weekend

- Waterspouts possible this weekend into early next week...

&&

.SHORT TERM /THROUGH SUNDAY/...
Issued at 431 AM EDT Sat Aug 23 2025

PATTERN SYNOPSIS/FORECAST:

Upper ridge retrograding over the Desert SW as a potent 557dm upper
low digs into the Upper Great Lakes, resulting in a generally
westerly 80kt upper jet across the northern tier of the CONUS...as
Post T.C. Erin heads out to sea well off the coast of New England.
Upper difluence over the Midwest atop a stretched-out and subtle
boundary with moisture pooling of higher pwats (around 1.5in) from
the Central Plains to the Upper Great Lakes/eastern Ontario, along
which some convective activity is re-firing as of 7z over northern
Lake Michigan into the EUP, where instability remains present over
the still-warm lakes amid subtle theta-e advection from upstream. A
second area of storms across the western UP trying to hold together
along the cold front itself, which stretches from central Ontario
down into southern MN. A second surface trough axis becoming
apparent near the International Border, behind which much colder air
exists...850mb temps falling toward +4C across central Canada.

Cold front to swing across the region this morning/midday from west
to east, with much cooler temps aloft (and at the surface) to
follow...at least, for most of the region, though the Saginaw Bay
area could see another day of warmer temps, pending the quickness of
fropa today. Aforementioned secondary trough to swing in late,
keeping instability in the fray, particularly with temps falling
aloft...leading to a potential second round of afternoon showers
(more lake-effect in nature) and additional shower activity
continuing right on into Sunday. Sharper trough axis swings through
Sunday, with a much colder air mass present...resulting in a very
fall-like end to the weekend.

Primary Forecast Concerns through Sunday:

Showers and Storms Today...Primary timeframe of concern for storms
is from now (7/8z) through 18z when we should have our best shot at
convective instability with the dry slot along/ahead of the cold
front...and with surface temps remaining on the warm side to keep
instability a bit better early in the day (a few hundred to perhaps
a thousand J/kg CAPE?). Deep-layer shear appears marginal (25-
35kts), which could be enough to try to organize storms today,
though there is some suggestion from soundings that a mid-level
inversion could keep convection from getting too rowdy. Think some
gusty winds will be possible with any storms, as well as perhaps
some small hail, given the cooling temps aloft.

A brief lull in the activity immediately behind the cold front
around midday/early afternoon should be followed by redevelopment of
potentially vigorous diurnal showers with the next niblet of energy
aloft/subtle surface troughing crossing the region later in the day
into the evening.

Think Sunday will be a downright fall-like day as the trough axis
swings in, with increasing low-level moisture behind it, leading to
a dreary and cool day with highs hanging on in the 60s. Not
impossible a few spots could fall short of 60 for a high, especially
the inland zones across the interior, where it should be cloudier
with northwest flow lake effect showers persisting.

Waterspout potential... Think waterspouts will be possible (perhaps
even likely) in this regime, perhaps as early as this afternoon,
given the cold air moving in aloft...particularly going into Sunday,
as delta-Ts fall toward 10-15C with periods of equilibrium levels
around 8-12kft.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Issued at 431 AM EDT Sat Aug 23 2025

Days 2-3 (Sunday night-Monday)...

Fall-like weather continues as unusually deep troughing settles
across the Upper Great Lakes (-3 to -4 standard deviations from the
mean) with unusually cold temperatures aloft to boot. While heights
should be rising as ridging slowly tries to build into the Upper MS
Valley Monday...will look for continued shower activity with
continued waterspout potential. Highs Monday will again hang out in
the unseasonably (but not entirely uncommonly) cool upper 50s to
lower 60s...likely resulting in lows Monday night in the 40s
(potentially colder if any areas are able to clear out, though not
sure winds will be calm enough).

Days 4-7 (Tuesday-Friday)... Another trough axis slips in Monday
night into Tuesday, which could flare up the lake effect potential
again. Does look like ridging and high pressure should start to
build in by Tuesday night and Wednesday, and will look for activity
to finally start to taper off. Lingering cold air mass, coupled with
high pressure slipping by, could lead to a much colder night Tuesday
night...may not be impossible a few sites come in in the 30s where
it is able to clear out and winds go light.

Another trough axis may try to approach the region Wednesday, with
potential for additional activity as we go into late week, though it
is unclear attm how this will evolve. However, signals point toward
cooler air hanging on through the remainder of the week.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 139 PM EDT Sat Aug 23 2025

Predominantly VFR conditions expected across the northern
Michigan terminals through the 18Z TAF valid time. Mainly
diurnally driven VFR CIGs will fade this evening, along with the
gusty westerly winds. Winds will increase again after daybreak
Sunday. CIGs will redevelop as well, along with scattered rain
showers.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory until 2 AM EDT Sunday for LHZ345-347.
     Small Craft Advisory until 2 AM EDT Sunday for LMZ323-342-
     344>346.
     Small Craft Advisory until 2 AM EDT Sunday for LSZ321.

&&

$$

SHORT TERM...FEF
LONG TERM...FEF
AVIATION...PBB