513
FXUS63 KAPX 212336
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
736 PM EDT Thu Aug 21 2025

.KEY MESSAGES...

-One last dry and warm day Friday with a southwesterly breeze.

-Cold front brings shower and embedded thunder chances later
 Friday night into Saturday, favoring the eastern U.P. and the
 Straits.

-Turning much cooler with well below normal temperatures amid a
 showery regime (partially influenced by lake effect processes)
 later Sunday through Monday.

&&

.SHORT TERM /THROUGH FRIDAY/...
Issued at 152 PM EDT Thu Aug 21 2025

Current Overview / Pattern Synopsis:

Northern Michigan remains sandwiched between two pretty potent
synoptic features... Hurricane Erin now making her departure off to
the north and east along the Gulf Stream from the Cape Hatteras
region, and a more potent longwave trough digging south and east
across the Canadian prairies. Closer to home, 1022mb surface high
over central upper Michigan along with ridging overhead is keeping
things on the dry side, with a stout 700mb subsidence inversion
reinforcing a cap across the region. Just a mix of higher based
cumulus, some looking quite agitated, but not enough to produce much
in the way of sensible weather. Anticipating lake breezes to be
active later this afternoon, particularly on the Lake Michigan side,
amid a NNE flow regime. As the troughing over central Canada works
closer, ridging is expected to fold south and east of the area,
leading to a decrease in heights. Surface reflection associated with
the troughing regime set to pass through northern Ontario, forcing a
cold front through the region late Friday night into Saturday, and
drumming up the next rain chances, and ultimately, the eventual
arrival of an early October like airmass.

Forecast Details:

Not much in the way of sensible weather the rest of today, though
with some of this stubborn cloud cover, highs probably settle in the
upper 70s to lower 80s, perhaps a degree or two cooler than guidance
has been depicting recently. That strong subsidence inversion will
remain in place, and with another night of modest radiational
cooling, it will be possible for some more patchy fog development,
though the extent of coverage is questionable due to the intrusion
of return flow disrupting the decoupling process. Regardless,
anticipating a breezy Friday, with SW winds pumping in the warm air
advection. Ample mixing may knock dewpoints down across northern
lower, but moisture pooling ahead of the boundary will lead to a
spike in dewpoints across the eastern Yoop with time through the day
Friday. Anticipating most shower and thunder activity to hold off
until later Friday night, so likely another dry day across the board
amid increasing cloud cover. Highs top out 80 to 87 (warmest NE
lower). For more details regrading rain chances and evolution Friday
night, please see the Long Term discussion below.

&&

.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
Issued at 152 PM EDT Thu Aug 21 2025

Surface cold front passes through the region from NW to SE with time
Friday night into Saturday afternoon. This uptick in forcing,
coupled with 500mb height falls will lead to the next rain chances,
though it won`t be overly widespread. As it stands right now, better
moisture and forcing will be displaced north toward the surface low
that will eventually mature and stall out over James Bay... thus,
anticipating the most favorable area for more widespread shower and
thunder coverage to favor eastern upper later Friday night into
Saturday morning, with just some scattered showers along and west of
I-75 / US-127. As one would expect, probabilistic guidance is
bringing better probabilities for at leas 0.50" of rain across
eastern upper, with values as high as 35%, with less than 10% probs
across the rest of the region. The front will be in the process of
making its passage Saturday, which should bring about a period of
cloudier, and perhaps somewhat more damp conditions to the region as
cooler air begins to spill into the region. Will have to see how
quickly the front is dispatched east to Lake Huron, as a slower
passage could bring about the potential for afternoon redevelopment
across northeast lower (specifically Saginaw Bay). Not a ton of
confidence in this for the time being, but something to watch.

The bigger story will be the cooldown and the ramp up in rain
chances... some by lake effect processes (*gasp*)... as the first
true bulldozer of colder air graces us with its presence Sunday and
beyond. For the time being, post frontal subsidence may actually
keep most dry early Sunday... aside from the lake effect precip
belts (declining to bust out the 4-letter S-word that rhymes with
"glow" for the time being). That is not anticipated to last long as
the longwave trough parks itself over James Bay. The first of
several embedded surface troughs will pass through the region late
Sunday afternoon into Sunday evening, which will really flare up the
precipitation activity across the board for a period. Anticipating
these waves of precip to continue (with embedded lake effect rain in
the belts between passages) through Monday before this feature makes
its exit. Tentatively, it looks like we will be dry by Tuesday, but
we all know lake effect likes to take its time when it departs. With
this feature, most areas probably see a prolonged rainfall of 0.25
to 0.50", but would not be surprising to see some rainfall well over
1.00" in the areas that bag the most persistent lake effect rain
showers. And now for those temperatures... Sunday looks like a
modestly decent day, with highs ranging from the mid 60s to mid 70s
before the bottom falls out on Monday... with highs struggling to
break 60. A slow warming trend commences, with highs poking above 70
across the board midweek and beyond.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 730 PM EDT Thu Aug 21 2025

Another quiet TAF period outside of BR/FG later tonight. Expect
patchy BR/FG to develop predominantly after midnight, with MVFR
to IFR VSBYs possible, perhaps brief CIGs below 010 as well in
the densest BR/FG. Any BR/FG should quickly diminish at around
or by 12Z with VFR conditions through Friday. CIGs will
steadily lower later Friday consequent of an increase in
moisture.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.

&&

$$

SHORT TERM...HAD
LONG TERM...HAD
AVIATION...JLD