856
FXUS63 KMQT 010747 CCA
AFDMQT

Area Forecast Discussion...CORRECTED
National Weather Service Marquette MI
347 AM EDT Tue Sep 1 2026

.KEY MESSAGES...

- Widespread dense fog is expected this morning during commuting
  hours. If you`re on the road, slow down and leave extra following
  room.

- Today will be warm and dry with gusts to 20 mph in the west. This
  will result in borderline elevated fire conditions in the western
  UP.

- Scattered rain showers are possible (20-40%) along the southern
  tier on Wednesday.

&&

.DISCUSSION...
Issued at 341 AM EDT Tue Sep 1 2026

GOES water vapor imagery this early morning shows a stream of
Pacific monsoonal moisture trailing across the UP as a closed 500mb
low enters into the province of Ontario. With most stationary land
and marine observation platforms showing near dead calm and dewpoint
depressions of 0 degrees, fog is pervasive across the CWA tonight.
All TAF sites currently show visibilities persistent at 1/4 mi or
less and ceilings at or below 200 feet, and METAR sites are
reporting fog or dense fog. With widespread fog currently evolving,
have hoisted a Dense Fog Advisory for most of the CWA.

High surface moisture should be alleviated into the morning hours as
the Ontario low tracks east, moving subgeostrophic flow and
subsidence over the area. The tighter pressure gradient associated
with the center of the low comes into closer proximity, causing
winds to increase as diurnal heating kicks in. All this to say, fog
is not expected to linger long into the morning. In fact, high
temperatures well into the 80s and resultant deep mixing with a dry
airmass aloft will lead to RHs dropping down into the high 20-
percents over the west this afternoon (40s/50s in the east). The NBM
shows over 90% probability of highs above 85F for much of the
western and southern UP, making this the warmest day the UP has had
in a while. Given gusts to 20 mph in the western and central UP
(higher in the Keweenaw), spots of borderline elevated fire
conditions may occur for a short while this afternoon.

As the Ontario low track east toward Quebec throughout the day
today, a weak front swings down from the northwest. As of now, a few
of the CAMs are suggesting isolated rain/thunder cells between 22Z-
00Z. Soundings are showing elevated CAPE above a small inversion
during the evening hours and a far from saturated atmosphere. Thus,
opted not to include this possibility in current PoP issuance.

Weak warm frontogenesis will occur Tuesday night/Wednesday morning
to our south as PWATs increase again to 1.25-1.50 inches, with
guidance mixed on whether associated rainfall will reach far enough
north into the UP. Best chances (up to 40%) over the south.

For late week into the Labor Day weekend, ridging builds over the
northern Plains, while a deep trough evolves over the Canadian
Maritimes. While this pattern is generally favorable for subsidence
over the local area, as evidenced by a high pressure ridge building
in from the northeast, western parts of the UP may be close enough
to the moisture/instability reservoir to see convection at times.
Currently capping out at 20-30% PoPs though, so the evolution is far
from certain.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 134 AM EDT Tue Sep 1 2026

Apart from stray high level cloud cover, skies are largely clearing
over the UP. Clear skies and light winds are in turn leading to the
development of fog and low stratus, with LIFR/VLIFR already at
the TAF sites; these conditions are expected to continue
through the night. An improvement to VFR is expected by mid-
morning Tuesday as skies clear out. Otherwise, light and
variable winds overnight will increase out of the west to
southwest Tuesday afternoon; gusts to 20 kts will be possible.

&&

.MARINE...
Issued at 219 PM EDT Mon Aug 31 2026

Lake Superior: There is the potential for dense fog at times through
tonight and will continue to monitor conditions for potential marine
dense fog headlines. Winds will be SE to 15 to 20 kts over the
eastern half of the lake today. Expect light winds of 20 kts or less
to return to Lake Superior tonight. However, SW winds of 20 to 25
kts could return between Isle Royale and the Keweenaw on Tuesday
before becoming 20 kts or less again Tuesday evening. The light
winds remain until potentially late on Thursday when NE winds of 20
to 25 kts possibly return to the western arm.

Northern Green Bay and northwestern Lake Michigan:  Winds will
generally be southerly 5-10kt today. A few strong to severe
thunderstorms are possible this afternoon and evening which could
product large hail and strong winds, however the probability is only
around a 5% chance. Expect mainly light winds to continue through
the rest of the week, although more showers and storms could return
on Wednesday.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Dense Fog Advisory until 9 AM EDT /8 AM CDT/ this morning for
     MIZ001>007-009>011-013-014-084-085.

Lake Superior...
  Dense Fog Advisory until 2 PM EDT this afternoon for
     LSZ245>247-251-265>267.

  Dense Fog Advisory until 11 AM EDT /10 AM CDT/ this morning
     for LSZ162-243-244-263-264.

Lake Michigan...
  Dense Fog Advisory until 2 PM EDT this afternoon for LMZ221-
     248.

&&

$$

DISCUSSION...RE/LH/Thompson
AVIATION...LC
MARINE...LH/NL