519
FXUS63 KAPX 171909
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
309 PM EDT Fri Jul 17 2026

.KEY MESSAGES...

- Air Quality Alert remains in effect through Saturday

- Showers/thunderstorms tonight/Saturday with passing cold front

- Stronger thunderstorm threat possible Monday

- Cooler weather settles in Tuesday/Wednesday.

&&

.DISCUSSION...
Issued at 309 PM EDT Fri Jul 17 2026

Pattern Synopsis/Forecast: Broad typical summertime ridging
encompasses much of the CONUS...with the notable exception of a
strong upper low (-3 sigma 500mb height anomaly) over Atlantic
Canada.  Troughing off the west coast as well...part of a larger
split long wave trough (weak +EPO/-PNA look).  Broad upper level low
circulating beneath the broad CONUS ridge over Texas...and causing
all of the flooding issues across the Hill Country.  Pacific-
dominant (southern branch) west-northwest upper level flow across
the Great Lakes...with a couple of upper level short wave
troughs/height falls in the northern branch flow across northern
Saskatchewan/Manitoba/ northwest Ontario.  Mid level short wave
trough across Manitoba extending south into North Dakota/
Minnesota...with low/mid level warm advection ahead of it. Strong
east-west low level moisture gradient across the upper Lakes this
morning...~20C 850mb dew point change from drier Lower Michigan west
into Wisconsin.  More importantly from an air quality perspective..
850/700mb winds are backing from northwest to southwest which
hopefully will nudge of the near surface smoke east/northeast later
today and improve things a bit.  Broad area of surface high pressure
encompasses much of the eastern CONUS...1008mb surface low over
northern Minnesota with a trailing cold front back across the
Dakotas and a warm front extending southeast into the Ohio
Valley/mid Atlantic.

Upstream northern branch short wave trough digs southeast and across
the upper Lakes Saturday.  Associated surface wave will pass east of
Lake Superior by Saturday morning and drag a cold front across
Michigan.  Back into the northwest flow aloft Sunday with ridging
building back into central Canada and surface high pressure settles
in over the Great Lakes/Midwest.  Split short wave trough off the
west coast today will propagate inland across Canada this weekend...
flattening the ridge and eventually sending stronger height falls
and a cold front across the state sometime in the Monday night/
Tuesday time frame.  This will eventually evolve into a long wave
trough getting carved out across eastern Canada and the northeast
quadrant of the CONUS for the latter half of next week.

Primary Forecast Concerns:

Air Quality Alert remains in effect through Saturday: Have
definitely seen an improvement in visibility this afternoon...along
with some lowering AQI values though still in the Unhealthy to Very
Unhealthy category.  KAPX VWP showing low/mid level winds backing to
the west/southwest today...and bringing in some better conditions
from the other side of Lake Michigan though better air quality is
still closer to the Mississippi River.  Winds remaining from the
southwest through tonight...along with precipitation helping scrub
the lower atmosphere to some degree...should allow conditions to
continue to improve (at least across northern Lower).  Cold front
passage Saturday morning will swing winds back around to the
northwest (with gusts 20-30mph)...with trajectories from the smoke
region over northwest Ontario so expecting a return of thicker smoke
and reduced air quality again starting late Saturday afternoon and
probably lingering into Sunday.  Air Quality Alert from EGLE has
already been extended through Saturday.

Showers/thunderstorms tonight/Saturday with passing cold front:
Scattered convection has been developing along the low level
moisture gradient this afternoon across northern Michigan to the
east of the warm front pressing eastward across Wisconsin/western
Upper.  May get a lull in this convection by early evening with
passage of a short wave trough at 700mb...but anticipate additional
thunderstorm development ahead of approaching cold front.  Heavy
rainfall a possibility across eastern Upper and the Tip of the Mitt
counties; axis of 1.75+ inch precipitable water values and K Indices
near 40 suggest an environment supportive of heavier downpours
though convection should be progressive.  Good bit of deep layer
shear in place as well tonight (30-40+kts 0-6km bulk shear) with
MUCAPE around 2000J/kg also suggestive of at least a large hail
threat with stronger embedded cells.  Think convection will mostly
be south of the Bridge Saturday morning as cold front sinks
southeast across northern Lower...with some low clouds and maybe
some drizzle across eastern Upper through midday Saturday. Remaining
convection (and later threat) expected to move into southern Lower
by early Saturday afternoon.

Stronger thunderstorm threat possible Monday: Probably more like
later Monday/Monday night ahead of next digging short wave trough
and thermal ridge...accompanied by stronger westerly flow/shear.
Already in the Day 4 15% outlook from SPC so an evolution worth
monitoring.

Cooler weather settles in Tuesday/Wednesday: Behind Monday`s system
looking at another push of colder with the potential for 850mb
temperatures dropping below +10C.  Looks potentially windy during
midweek especially Wednesday with strong cold advection...and warm
lakes which looks marginally interesting from the perspective of
kicking off some lake induced showers Tuesday night/Wednesday.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 132 PM EDT Fri Jul 17 2026

Widespread visibility restrictions should continue to improve
through the issuance period as wind directions shift more
southerly and shower/storm chances increase region-wide.
Scattered showers are noticed on radar currently, with
additional showers expected later on tracking north to south,
with the potential for some stronger storms to develop into
tonight. Within any stronger storms, conditions may deteriorate
(particularly visibilities) with heavy rain and gusty winds
being the main threats. Otherwise, light winds into this
evening, with southwest winds becoming a bit gusty later
tonight, and shifting northwest as we head into Saturday
(remaining gusty) and potentially bringing that smoke right back
into the region as we progress through Saturday.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory from 5 AM Saturday to 5 AM EDT Sunday for
     LHZ347-348.
     Dense Smoke Advisory until 11 PM EDT this evening for LMZ323-
     341-342-344>346.
     Small Craft Advisory from 5 AM Saturday to 5 AM EDT Sunday for
     LSZ321.

&&

$$

DISCUSSION...JPB
AVIATION...NSC