656
FXUS63 KAPX 122334
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
734 PM EDT Sat Sep 12 2026

.KEY MESSAGES...

- Cold front passage late this afternoon/evening.

- Cooler with shower chances Sunday.

- Dry Monday with more substantial rain threat Monday night/
  Tuesday (and possibly beyond but much uncertainty regarding
  that).

&&

.DISCUSSION...
Issued at 302 PM EDT Sat Sep 12 2026

Pattern Synopsis: Broad long wave trough in place across western/
central North America; stronger short wave trough/PV anomaly over
northwest Ontario with another digging southeast across the Prairie
provinces.  Water vapor imagery also shows a weaker short wave
trough crossing the Dakotas.  Weak upper low over the lower
Mississippi/Tennessee River Valleys.  Positive tilt/-PNA trough over
the Pacific Northwest and adjacent Pacific Ocean...trying to pick up
an old cut off low northeast of Hawaii and pull it back into the
"PV reservoir" so to speak.  This attempt looks like it will be
unsuccessful...but the remnants of the Pacific Northwest short wave
trough will feature prominently in Great Lakes weather during the
first half of the coming week.  Strong -EPO ridge south of Alaska
(+3 sigma 500mb height anomaly) poking northeast into the Canadian
Territories. Narrow axis of 1.25-1.50 inch precipitable water values
and steeper mid level lapse rates extends from the upper Lakes
southwest into the Central Plains ahead of cold front...with
cold/dry air advection behind it across the northern Plains/upper
Midwest.

Primary Forecast Concerns:

Cold front passage late this afternoon/evening: Cold front at 1800Z
ran from a MQT-GRB-DBQ line...with a pre-frontal wind shift moving
into Lake Michigan.  Water vapor imagery shows upward motion field
with short wave trough north of Lake Superior spreading across Upper
Michigan and toward Lake Michigan.  Getting an increase in cloud
streets bubbling up across Lower Michigan...with a few hundred J/kg
of MLCAPE west of the I-75 corridor along with decreasing CINH.  So
expect the threat for scattered showers/thunderstorms to continue
until the cold front and short wave trough depart the area this
evening.   Narrow band of post-frontal St/Sc will give way to some
lake induced Sc overnight as 925mb temperatures sink below +12C.

Cooler/breezy with shower chances Sunday: Next short wave trough in
the series...digging southeast out of the Canadian Prairies this
afternoon...will swing across the upper Lakes Sunday.  850mb
temperatures dropping below 4C across Lake Superior will result in a
decent amount of lake-induced instability.  Combined with larger
scale forcing/moisture will likely get showers going off Lake
Superior Sunday morning.  For now expect rain chances will be lower
south of the Straits Sunday afternoon...won`t rule it out given the
strength of the forcing but the instability/moisture profiles across
northern Lower not as impressive.  Wondering how much of the lake
component will linger into Sunday evening.  High temperatures in the
70s and lower 80s this afternoon will give way to highs mainly in
the 60s for Sunday (with highs 70-75 across far southeast portion of
the forecast area closer to Saginaw Bay).  Winds also expected to be
gusty with mixing during the day...west/northwest gusts 20 to 30 mph
anticipated.

Dry Monday with more substantial rain threat Monday night/Tuesday
(and possibly beyond but much uncertainty regarding that):  High
pressure centered over Michigan Monday gives way to deep layer
southwest flow Monday evening...low level jet directed into the
upper Lakes with precipitable water values at or above 1.75 inches.
Main focus Monday night will be across Upper/northwest Lower
Michigan...then shifting into central and northeast Lower as the day
progresses Tuesday.  Trends continue to suggest drying across Upper
Michigan during the afternoon Tuesday...remains to be seen how
aggressively this pushes into northern Lower (more on that below).
Highest probabilities exceeding 1 inch rainfall/24 hours ending
0000Z Wednesday remain across eastern Upper and the Tip of the Mitt
counties.  Probably some much needed rain across eastern Upper where
things have been quite dry over the past two weeks (less than 25
percent normal precipitation) with some spots of D1 (moderate)
drought showing up.

Evolution beyond Tuesday afternoon is rather interesting...with an
upper anticyclone become established over the southeastern U.S.
Monday...and then expanding north with 594dam 500mb heights knocking
on the door of southern Lower Tuesday.  This will set up a
baroclinic zone across the upper Lakes during midweek...a
synoptically ideal setup for a corridor of heavier rain potential.
Exactly where this sets up will determine if our southern zones get
clipped by this.  For now the forecast is dry for Wednesday...with
rain returning Thursday.  There are some very small probabilities of
>2 inches of rain Wednesday night/Thursday south of M-32.  So
something to keep an eye on going forward.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 734 PM EDT Sat Sep 12 2026

Some MVFR cigs will be seen for another couple hours at PLN, but
that and any leftover showers will otherwise quickly depart.
Clouds return Sunday, with a chance for showers by afternoon,
especially CIU/PLN. Winds lighten into tonight. Nw breeze
returns Sunday.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...Beach Hazards Statement until 8 PM EDT this evening for MIZ025-
     031-095-098.
MARINE...Small Craft Advisory until 8 PM EDT this evening for
     LHZ345>347.
     Small Craft Advisory until 8 PM EDT this evening for LMZ323-
     341-342-344>346.
     Small Craft Advisory until 8 PM EDT this evening for LSZ321-
     322.

&&

$$

DISCUSSION...JPB
AVIATION...JZ