963
FXUS63 KMQT 231829
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
229 PM EDT Sun Aug 23 2026

.KEY MESSAGES...

- A Beach Hazard Statement is in effect today for the shorelines of
Marquette and Alger Counties due to strong winds and high waves
creating dangerous rip currents and swimming conditions.

- Spotty light lake effect rain showers/sprinkles are possible over
the east half through this evening.

- The next chances for widespread showers and thunderstorms arrives
in the west Tuesday PM, spreading east overnight and ending for most
late Wednesday.

- Seasonable temperatures are expected through the week with the
exception of slightly below normal temperatures today and tonight.
Some patchy frost is possible in the typical cold spots and elevated
surfaces in the interior west tonight.

&&

.DISCUSSION...
Issued at 228 PM EDT Sun Aug 23 2026

Late morning GOES-East Day Cloud Phase RGB imagery and KMQT radar
reflectivity show a few bands of isolated to scattered light rain
showers this morning over mainly the central UP with bands of clouds
across the rest of the UP. Temperatures at 850mb of around 5 C are
above a Lake Superior that ranges from 12 C to 20 C, which ranges
from "good enough for lake effect clouds" to "good enough for lake
effect showers", reflecting the variable effects of lake effect that
is ongoing this morning. Impacts will be low to none as the showers
are not particularly intense, but it may keep temperatures from
breaking out of the 60s today for all except for the south-central
and Isle Royale which will see less clouds today. The brisk
northwesterly flow today will continue, and the wind-driven waves of
5-7 ft east of Marquette from 1-5 miles out from the shores will
drive a high risk of dangerous swim conditions including rip
currents.

RAP analysis shows a 1004mb low pressure over the Ontario/Quebec
line with broad 1018-1020mb high pressure stretching from far
northwestern Ontario to Missouri. The low is vertically stacked with
deep 500mb troughing extending over much of eastern North America,
opposed by a 500mb ridge spanning from the Four Corners region to
the Canadian Prairie. While the trough will not be moving much
tonight, the ridge axis will pivot from the Canadian Prairie
towards the Manitoba/Ontario line, which will advance the high
pressure towards the UP and clear out skies for most after 00Z.
As the high brings relaxing winds, efficient radiational cooling
will allow temperatures to plummet in the interior west
tonight, with a few interior western locations reaching the mid
30s (wouldn`t be surprised if Alberta Ford Center or other
traditional cold spots dipped to freezing). This will result in
some patches of frost (especially on elevated surfaces or low
spots where cold air pools), however, with the prior August heat
still hanging on in the soil temperatures, widespread frost is
not forecast, so an advisory will not be sent this shift.
However, some caution should still be taken for those in the
interior west with sensitive vegetation. Also, with temperatures
falling overnight, a few patches of fog cannot be ruled out in
areas sheltered from the wind in the west (around 20% chance).

As high pressure establishes itself over the region, dry weather and
seasonable temperatures are expected Monday into Tuesday. Meanwhile,
a 500mb trough currently over eastern Washington and southeast
British Columbia will complete its journey around the northern
periphery of the western CONUS ridge, arriving around the Northwest
Angle Tuesday afternoon. This will drive significant PVA and also
support a surface low of 1005-1010mb arriving near western Lake
Superior by 00Z Wednesday. Moisture advects into the region ahead of
the cold front and PWATs climb to 1-1.25 inches. Directional wind
shear will certainly be present as southerly to southwesterly low
level flow is contrasted with the westerly to northwesterly flow
aloft, though speed shear is somewhat lacking as LREF 500mb winds by
00Z Wednesday around the interior west are only around 25 kt.
Instability is likely going to be sufficient for thunderstorms as
Euro ensemble MUCAPE is 40-60% likely to exceed 750 J/kg for the far
western UP by 00Z Wed. Instability probabilities fall off overnight,
but by 18Z Wed, mean MUCAPE values for the east half are widespread
over 1000 J/kg, though uncertainty in the available forcing by
Wednesday afternoon to realize such an uncertain airmass (and paltry
shear profiles to organize buoyant updrafts) casts doubt on the
severe weather potential, though unorganized thunderstorms with
plenty of available moisture can still bring notable rainfall, with
the LREF probability of 0.5+ inches of rain by 06Z Thursday
widespread 40-70%.

With 850mb temperatures around 60% likely to fall to around 8 C,
some lingering light lake effect showers (or at least, cloud cover)
is possible for Thursday into Friday. Models diverge on solutions
beyond then as different members of different ensemble suites handle
the persistent Four Corners ridge and troughs over Hudson Bay and
southwestern Canada differently, but at least some period of ridging
seems reasonable to bring dry weather to the UP to kick off the
weekend before the next ridge-riding shortwave arrives.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 207 PM EDT Sun Aug 23 2026

Mainly VFR conditions are anticipated at all three sites for the
period, with the exception of visibility restrictions at IWD prior
to dawn and MVFR ceilings at SAW this afternoon due to to lake
enhanced clouds and showers. At KIWD, LAMP LIFR ceilings and
visibility probabilities run around 15% for the pre-dawn period;
given very low winds and a moist atmosphere, included BR in TEMPO
group for this site. At KCMX, gusty northerlies lay down a bit
overnight. At KSAW, expecting ceilings to bounce between VFR and
MVFR this afternoon as showers are generated from onshore northerly
flow; these should clear out as diurnal heating increases throughout
the day.

&&

.MARINE...
Issued at 228 PM EDT Sun Aug 23 2026

Northwest wind gusts continue especially over the east half of Lake
Superior at 25-30 kt into tonight, with European ensemble
probabilities of gales at 15 percent or less. Wind gusts linger
around 20-25 kt early Monday before falling below 20 kt Monday
afternoon through Tuesday afternoon with high pressure settling over
the region. Southerly to southeasterly wind gusts of around 25 kt
pick up Tuesday night ahead of an approaching cold front, with winds
turning northwesterly behind the front by Thursday morning,
including a few gale force gusts to 35 kt possible (20-40% chance
particularly south of Stannard Rock). Winds quickly relax below 20
kt Thursday night into Friday as uncertainty in the forecast grows
into the weekend. Along the midweek cold front will be 20-40%
chances of thunderstorms. Ongoing waves of 4-7 ft fall below 3 ft
Monday afternoon before increasing again to 4-7 ft in the southeast
part of the lake Thursday morning through Thursday night.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Beach Hazards Statement until 10 PM EDT this evening for
     MIZ005-006.

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

&&

$$

DISCUSSION...GS
AVIATION...RE
MARINE...GS