933
FXUS63 KMQT 301827
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
227 PM EDT Sat Aug 30 2025

.KEY MESSAGES...

- Patchy dense fog is possible across the interior portions of
  Upper Michigan tonight.

- Isolated showers and thunderstorms are possible (~20% chance)
  west half Sunday and Monday afternoons.

- A cold front will move through the region Tuesday night and
  Wednesday. This will bring widespread rain to Upper Michigan
  and strong winds to the Keweenaw.

- A cool airmass will build over the Upper Greats late this
  week.

- There is a 25-60% chance for northwest gales Tuesday night
  into Wednesday, mainly west and north of the Keweenaw
  Peninsula.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 123 PM EDT Sat Aug 30 2025

High pressure over the area while a mid-upper level low spins to the
east is keeping the region region dry today. Under these mostly
clear skies, temperatures have climbed into the upper 60s to low 70s
for most of the region. Winds have been mostly light and variable
this morning. For the rest of today, additional warming into the mid
70s and an afternoon lake breeze are expected. Dry conditions will
prevail. Tonight, temperatures should dip down into the 50s by the
lakes and upper 40s interior where patchy dense fog may develop by
morning.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Issued at 227 PM EDT Sat Aug 30 2025

An expansive mid-upper level ridge will stretch across the Upper
Great Lakes through at least Tuesday. With 1020-1025mb ridging over
the region thanks to a surface high slowly stretching eastward
through the Great Lakes into New England, mostly dry conditions are
expected in Upper Michigan. There are 2 potential exceptions though:
Sunday and Monday afternoons. Both days, weak retrograding vort
maxes alongside daytime instability growing to ~1000j/kg,
potentially higher Monday, may yield isolated to scattered showers
and thunderstorms along the lake breeze boundaries of north-central
and western Upper Michigan. Deep layer shear overall looks to be
weak, so strong or severe storms are not anticipated should
convection develop. Steady 850mb temps of 11-13C Sunday-Tuesday will
produce temperatures in the mid to upper 70s for most of the region.
Although increasing clouds on Tuesday may result in highs only
peaking in the low 70s in some locations across the west half.
Overnight lows Sunday and Monday night will fall into the mid to
upper 50s near the lakeshores and in the Keweenaw and then to near
50F away from the lakeshores.

A pronounced upper level low is expected to dive southeast through
Manitoba and Ontario late Tuesday and Wednesday. 0z and 12z
deterministic guidance suggests this feature will park over the
Upper Great Lakes Wednesday night into Thursday as it takes on a
negative tilt, then lift north and northeast into Hudson Bay through
Friday night. There`s more ambiguity in the surface features, but
the overall consensus is a deepening low will develop along a
descending cold front late Tuesday. The low, or a secondary surface
low, will move through or near Upper Michigan/Lake Superior
Wednesday or Wednesday night before being pushed northward Wednesday
night, potentially retrograding Thursday over northern Ontario, then
finally exiting northeast into Hudson Bay Friday night. Despite
being 4+days out, this general evolution is handled well by the
deterministic and ensemble guidance suites. This includes the cold
front moving through Upper Michigan Wednesday, resulting in a large
swath of precip spreading across the area ahead of the boundary, and
the stronger wind signal for the Keweenaw, which may result in 30-40
mph wind gusts Wednesday. Additionally, model run to run consistency
includes a surge of cooler air filling in behind the front,
resulting in below normal temperatures to finish off the work week.
Exactly where the coldest air ends up is still a question, but the
general idea is for 850mb temps to fall to +1 to -3C. This will
yield daytime highs in the 50s or low 60s and overnight lows in the
40s by the lakes and 30s interior. Suspect frost could be a concern
toward the latter half of the week, although the cooler temps aloft,
continued cyclonic mid-level flow, potential for a secondary surface
trough, and lake effect/enhanced rain, may work against significant
overnight cooling in some locations.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 123 PM EDT Sat Aug 30 2025

VFR conditions and light winds will prevail at all sites this
afternoon and evening. Expecting VFR to continue at KCMX/KIWD
overnight into Sunday while fog developing overnight may result in
IFR visibilities at KSAW.

&&

.MARINE...
Issued at 227 PM EDT Sat Aug 30 2025

High pressure ridging over the region will, overall, result in winds
below 20kts for a majority of the period through Tuesday morning. By
afternoon on Tuesday, increasing pressure gradient will allow for
increasing southwesterly winds across the western and northern
portions to build to near 20kts. A cold front will move move through
the region late Tuesday/Tuesday night into Wednesday. Behind the
front, winds will quickly become northwest and increase as cooler
air builds over Lake Superior. Guidance continues to suggest the
potential for gales Wednesday. Latest ensemble guidance packages
vary, but generally suggest 25-60% chance of NNW or NW gales Tuesday
night and Wednesday. Highest probabilities are located west of the
Keweenaw between the peninsula and Isle Royale and lesser amounts
northeast and east of the Keweenaw Peninsula. Northwest to westerly
flow will persist over the lake for the remainder of the week,
slowly falling below 20kts by late Friday.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.

&&

$$

SHORT TERM...JTP
LONG TERM...JTP
AVIATION...JTP
MARINE...JTP