277
FXUS63 KMQT 122337
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
737 PM EDT Sat Sep 12 2026

.KEY MESSAGES...

- A few light showers in the east diminish this afternoon.

- Cooler on Sunday with isolated to scattered showers in the north
half.

- Chilly Sunday night with patchy frost in the interior.

- Widespread rain moves into the UP from west to east late Monday
into Monday night, ending Tuesday morning.

&&

.DISCUSSION...
Issued at 140 PM EDT Sat Sep 12 2026

Early afternoon water vapor and RAP imagery show a closed upper low
over southwestern Hudson Bay (500 mb heights at 10pctl of climo)
with strong zonal flow over the northern tier of the west half of
the CONUS. Band of clouds associated with departing moist axis is
over the eastern half of the UP with clearing skies to the west.
Surface front is coincident with this band of clouds, along which a
band of showers/sprinkles is occurring from eastern Alger SW through
Dickinson County. Cannot rule out an isolated TS over
Schoolcraft/Luce through early this afternoon with dewpoints in
the low to mid-60s and SBCAPE 500-1000 J/kg per SPC
Mesoanalysis. Otherwise, winds shift NW behind the front,
ushering in a cooler and drier airmass as lower heights
associated with the Hudson Bay low pivot across the upper Great
Lakes. LREF mean 850 mb temps fall to 2- 3C over Lake Superior
on Sunday, which is 15-20pctl of climo, and should result in
some lake-induced instability with surface to 850 mb delta-Ts
around 13C. CAMs show lake-effect rain showers developing during
the late morning into afternoon, particularly over the east
half as the dry column will be more prominent over the west.

Sunday night, ideal radiational cooling conditions develop as PWATs
fall to 0.3-0.4 in (5-10pctl of climo) associated with a building
~1025mb high. Have reduced lows relative to NBM guidance Monday
morning, with widespread 30s in the interior and patchy frost
expected.

Another closed upper low shifts from the northern Rockies into
central Canada early next week, with a strong LLJ feeding Gulf
moisture poleward ahead of it. This will boost PWATs up to 1.5-1.75
inches Monday night, and an area of rain will move from west to east
along the nose of the LLJ across the UP late Monday into Monday
night. This looks to be a fairly quick-hitting system with most of
the rain having exited east of the UP by Tuesday morning, but should
provide at least a wetting rainfall for the entire area. A blend of
LREF and NBM probs of > 0.50" in 24 hours are 50-80%, and > 1.00"
are 30-50%, lowest over the Keweenaw and highest over the south-
central. Cluster analysis shows variability with respect to precip
amounts is tied to the 500 mb heights in central Canada - a deeper
trough resulting in a stronger low actually results in a drier
solution for the UP, possibly due to the LLJ forcing moving through
quicker.

Temps should be fairly seasonable on Monday, and a sneaky warm day
is possible Tuesday with mixing into warm temps aloft in the wake of
the Monday night system. The rest of the week looks fairly
seasonable as we are favored to be on the northern extent of the
persistent positive height anomaly over the south-central US,
although proximity of a moisture plume along the edge of this
high means we can`t rule out some rain toward the middle/end of
the week.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 737 PM EDT Sat Sep 12 2026

VFR conditions expected through the period with high clouds
beginning to stream across Upper Michigan from the west this
evening. Gusty west winds diminish below 10 kt at KIWD and KSAW by
02-03z this evening, but stay around 10-15 kt at KCMX tonight. A
weak disturbance passing to the north will bring a slight chance for
rain showers over the area Sunday morning, but chances are low
enough to not include a PROB30 at any of the terminals. Cigs may
lower to FL035-060 during this time but are expected to stay VFR.
West-northwest winds become gusty again on Sunday afternoon, gusting
to 25 kt at KIWD and KSAW and 30 kt at KCMX.

&&

.MARINE...
Issued at 140 PM EDT Sat Sep 12 2026

Lake Superior: Westerly winds behind a cold front continue today
with 25-30 kt common, and a few gusts touching gale force cannot be
ruled out. Winds may relax somewhat tonight, but the arrival of a
pocket of cold air aloft will cause stronger winds to mix to the
surface on Sunday, with 25-30kt W-NW winds expected again, and a few
gusts to 35 kt over south-central portions of the lake. Significant
wave heights of 3-6 feet will be common. Small craft advisories
remain in effect through Sunday. High pressure briefly results in
diminishing winds Sunday night into Monday, but strong southerly
winds will increase through the day on Monday as the high shifts
east. Although stability will be increasing, temperatures should be
cool enough at the onset to mix some of the stronger low-level jet
winds to the surface, with a 50-70% probability of southerly gales
developing over the east half of the lake Monday night, likely
peaking around 40 kt. A brief period of westerly gales is likely (50-
70%) in the vicinity of the Keweenaw to Stannard Rock on the back
side of this system on Tuesday, with winds quickly diminishing
Tuesday night.

Northern Green Bay and northwestern Lake Michigan: Winds and waves
should continue diminishing for the rest of today into tonight as
they shift westerly. However, northwesterly winds will increase to
near Small Craft Advisory criteria on Sunday as colder air aloft
moves over the waters. Winds diminish Sunday night as high pressure
builds in, but the next period of active marine weather occurs late
Monday into Monday night with strong S-SW winds developing.
Probability of gales is 30-40% at this time Monday night, and waves
build to around 6 feet in the bay, and 6-10 feet in the nearshores
of Lake Michigan. Wind and waves gradually diminish through the day
Tuesday as they shift westerly.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Beach Hazards Statement until 8 PM EDT this evening for MIZ014.

Lake Superior...
None.
Lake Michigan...
None.

&&

$$

DISCUSSION...Thompson
AVIATION...CB
MARINE...Thompson