141
FXUS63 KMQT 010536
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
136 AM EDT Tue Sep 1 2026

.KEY MESSAGES...

- Showers and thunderstorms are possible starting around 00z this
evening. There is a marginal risk (~%5 chance) of severe
thunderstorms over the southcentral and central UP during this time.
The main severe threats with these storms are large hail, damaging
wind, and heavy rain.

- Warm and dry Tuesday with highs in the 80s. The rest of the week
will not be as warm, but still above normal.

&&

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

The upper level low pressure over southern Saskatchewan will move
east to western Ontario by late tonight, weakening as it continues
to occlude. Deep moisture is expected to remain in place as mid-
level lapse rates steepen as instability increases to 2500-3000 J/kg
over the south-central U.P. by the most likely time of initiation
around 00z. Surface-500mb shear is expected to increase to 40-45kts
by this time as well. Thus, the instability and shear are present
for the potential development of a severe thunderstorm, if initiation
occurs. However, given that most models indicate a capping inversion
over much of the central U.P. through this evening and that only
minimal lift is expected as the boundary continues to occlude as it
passes through, thunderstorm development could be limited to only
those storms that are strong enough to break the cap. The 1630z
update of the SPC outlook continues the Marginal (5%) chance for
sever thunderstorms across the central U.P. The main hazards with
any storms that develop will be large hail, damaging wind, and heavy
rainfall.

Lows tonight are expected to be in the upper 50s inland and low 60s
near the lakeshore. Some patchy fog is possible for the central and
eastern U.P. after the passage of any thunderstorm, potentially
lingering into the early morning hours Tuesday. The western U.P. can
expect clearing skies and falling humidities overnight.

The upper low will shift east on Tuesday into central Ontario.
Significant drying noted on Advanced Layer Precipitable Water
imagery will spread into the area, with PWATs falling to around 0.75
inches. Deep mixing into this dry atmosphere is forecast, with
relative humidity values falling into the upper 20s/low 30s (%) over
the west half, with wind gusts of around 20 kt in the afternoon. In
consultation with fire weather partners, will hold off from issuing
an SPS at this time due to unsupportive fuel indices. It will be
warm with highs ranging through the 80s, 10-15 degrees above normal
in most spots. It will also continue to be fairly humid for the east
half with wind flow off of Lake Michigan.

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 60%) 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...
None.
Lake Superior...
  Dense Fog Advisory until 11 AM EDT /10 AM CDT/ this morning
     for LSZ162-243-244-263-264.

Lake Michigan...
None.

&&

$$

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