447
FXUS63 KMQT 200500
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
100 AM EDT Wed Aug 20 2025

.KEY MESSAGES...

- Areas of patchy and locally dense fog are expected tonight
  through Wednesday morning.

- Dry weather expected Wednesday and Thursday before the next
  chances of showers and thunderstorms return to the UP Friday.

&&

.SHORT TERM /THROUGH WEDNESDAY NIGHT/...
Issued at 254 PM EDT Tue Aug 19 2025

GOES satellite and RAP analysis reveal plenty of clouds overhead the
Upper Great Lakes as weak troughiness is in place overhead ahead of
an incoming upper ridge and plenty of low level moisture lingers. So
far today, light winds, drizzle, fog, and overall dreariness has
been observed along with afternoon temps clocking the upper 60s to
low 70s. More of the same will continue tonight with an expected
increase fog development through the earlier morning hours. Areas of
patchy to dense fog may locally reduce visibility below 1 sm, so
take caution if traveling tonight and or during tomorrow morning`s
commute.

Through Wednesday, the encroaching upper ridge will support sfc high
pressure building south from Ontario across Lake Superior, ushering
in a drier airmass and slowly eroding cloudy conditions through the
afternoon and evening hours, though guidance hints at additional fog
and low clouds developing, particularly across the northerly upslope
locations of the central and western UP. Otherwise, dry weather and
light northerly flow will be the rule. Daytime temps once again
reach the upper 60s to low 70s. Overnight lows cool to the 50s
across the interior, closer to 60 along the lake shores.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
Issued at 254 PM EDT Tue Aug 19 2025

By 00z Thursday, ~1020mb sfc high pressure will be placed solidly
atop Lake Superior as a digging trough in the Canadian Rockies and
stout upper ridge over the Four Corners amplify heights over the
central CONUS. With this, quiet weather and a brief warm up is
expected Thursday and Friday. 850 temps reaching 13-15C will allow
daytime temps under sunny skies to climb near the 80 degree mark.
The next chance for precipitation across the Upper Peninsula arrives
sometime Friday evening as the aforementioned Canadian Rockies
trough swings southeast into western Ontario by 00z Saturday,
sending a cold front across the region that may kick off showers and
thunderstorms. Behind the cold frontal passage, modest cold air
advection aloft spills across Lake Superior. 850 temps fall below
10C Saturday and even further towards 5C by the end of the weekend
into early next week. With average lake temps near 17-18C, would not
be surprised to see some lake effect/enhanced clouds or precip as
multiple passing shortwaves embedded within the adjacent closed
low press through the Upper Great Lakes this weekend.
Additionally, gusty W to NW winds and cooler temps aloft will
bring in cooler daytime temps in the 60s to upper 50s
Sunday/Monday with overnight lows in the 40s away from the
lakeshores.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 100 AM EDT Wed Aug 20 2025

Ceiling and visibility restrictions to persist at all TAF sites
through this morning as moist northerly flow continues to support
fog and low clouds. Currently, VFR has briefly returned to CMX, but
anticipate that site to deteriorate to LIFR again in the Wed 06-09Z
time frame along with both IWD and SAW. IWD could see a return to
MVFR by mid-morning, but not much improvement is expected at CMX
or SAW.

&&

.MARINE...
Issued at 133 PM EDT Tue Aug 19 2025

Light winds becoming northerly by tonight will hold below 20 kts
through tonight. Patchy fog is expected over much of the lake during
this period, becoming dense at times to 1 mi or less into Wednesday
morning. A Dense Fog Advisory has been hoisted for much of the
central lake through this evening, but extending and expanding of
the advisory is anticipated to capture increasing visibility
deterioration into Wednesday.

Variable winds less than 15 kts are expected for Wednesday and much
of Thursday as high pressure builds overhead. Southerly winds
increase Thursday night as troughing develops to the west, becoming
southwest up to 20 kts for Friday as high pressure shifts to the
Lower Great Lakes. A low pressure system then tracks over northern
Ontario this weekend, sending a cold front across the lake Friday
into Saturday and reintroducing west becoming northwest winds into
the 20-30 kt range for Saturday and Sunday as a seasonably cold
airmass settles in. Significant wave heights are expected to
increase to 4-6 ft as a result of persistent winds. Gales to 34 kts
are currently unlikely (<15% chance), but will continue to monitor
this period.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
  Dense Fog Advisory until 4 AM EDT early this morning for
     LSZ263-264-266.

Lake Michigan...
None.

&&

$$

SHORT TERM...BW
LONG TERM...BW
AVIATION...TDUD
MARINE...Jablonski