490
FXUS63 KMQT 031055
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
655 AM EDT Wed Sep 3 2025

.KEY MESSAGES...

- A cold front will continue through the region today. This will
  bring widespread light to moderate rain and breezy winds to
  Upper Michigan, with the Keweenaw having the greatest wind
  gusts (30+ mph).

- A cool airmass will build over the Upper Great Lakes the rest
  of this week, providing the region below normal temperatures
  all the way to the week`s end.

- Gales to 35 knots are expected over Lake Superior today,
  mainly north and perhaps west of the Keweenaw Peninsula.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 353 AM EDT Wed Sep 3 2025

As the main line of convection associated with the cold front
descending over us continues to push into the eastern half of the
U.P. this morning before departing for Ontario, expect temperatures
to remain fairly mild for the next few hours as the bulk of the cold
air advection is just now (as of the time of this writing) entering
the Arrowhead of Minnesota. While some showers and an occasional
rumble of thunder or two is being seen via radar behind the main
line, convection doesn`t look to pick back up again all that much
until the colder temperatures arrive later this morning. According
to the latest guidance, it seems that temperatures really start
dropping from northwest to southeast across the U.P. around dawn; as
that happens, expect the lows for this morning and highs for today
to simultaneously occur as temperatures will continue to lower
throughout the day. Given the strength of the cold air advection and
gusty winds off of Lake Superior, expect the generally northwesterly
winds to gust up to 20 to 25 mph across the area by this afternoon,
with the Keweenaw gusting up to 30 mph or higher at times. In
addition, with 850mb temperatures dropping into the -3 to +1 C range
today, expect lake enhanced/effect rainfall to develop over the
northwest wind belts, continuing through the overnight hours too as
cold air advection continues to cycle across the region. While the
rainfall is expected to be rather light, there is enough to be
wetting (0.10-0.20") across the northwest wind belts today and
tonight.

Outside of the rain and cooler conditions today, given then strong
winds over the Great Lakes today (especially Lake Superior), a Beach
Hazard Statement has been issued for Marquette, Alger, and southern
Schoolcraft counties; stay safe and out of the water! Once we move
into the overnight hours, expect the lake effect rain showers to
become more confined to the northwest wind belts as the moisture
with the system begins to depart and winds also weaken a tad. In
addition, we may see a patch of frost or two pop up in the south
central or along the Wisconsin in spots where the cloud cover
ceases; however, given the lake effect cloud cover and breezy
conditions expected, even during the overnight hours, these spots
will be VERY isolated if they even occur. With the lake effect cloud
cover over most of the area tonight, we get insulated a little bit.
HOwever, with anomalously cold temperatures moving over us today and
remaining through the overnight hours, expect lows to drop down into
the mid 30s in the interior areas.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
Issued at 356 PM EDT Tue Sep 2 2025

It will feel much like fall into at least the early weekend with
cool, breezy conditions along with lake effect rain showers at
times. A stronger cliper-like low could bring a round of widespread
rain to the U.P Thursday night into Friday as it moves through the
area. Winds will shift westerly on Thursday with most lake effect
shifting into the west wind belts.

Thursday night into Friday a clipper-like low will swiftly move
southeast out of Alberta into the the Upper Midwest and Great Lakes
region. There is still uncertainty with the exact track of the low
but overall impacts should be low with this system.

Expecting lingering lake effect showers to diminish though the day
on Saturday with dry and cool weather for Sunday. Monday will be see
temperatures moderating into the 60s for most of the U.P.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 655 AM EDT Wed Sep 3 2025

Expect conditions at the terminals to generally be non-VFR the next
24 hours as we transition to lake enhanced and lake effect rain
showers over the northwest wind belts. LIFR to IFR conditions this
morning do eventually look to improve to MVFR across the area this
afternoon, although some terminals like CMX may take their sweet
time doing so (if they even do improve). As we transition to pure
lake effect rainfall tonight, expect rain chances to end at SAW late
in the evening, potentially bringing cigs back up to VFR near the
end of the period. However, given that lake effect cloud cover is
still expected to be over the area throughout the next 24 hours, and
LAMP guidance keeps things socked in at 2500`, decided to follow the
LAMP guidance and keep SAW high-end MVFR late tonight. Depending on
the wind direction, IWD may get out of the lake effect showers and
cloud cover late tonight too, but uncertainty on that is high at
this time given that a subtle change in the winds could completely
change flight categories (and weather conditions too).

Gusty northwesterly winds are expected to dominate today into
tonight behind a cold front moving through Upper Michigan this
morning. While we may see winds weaken late tonight due to cold air
advection slowing down and the pressure gradient weakening,
confidence on the weakening surface winds is very shaky as model
skew-Ts for the terminals show that mixing could still occur from
time to time during the overnight hours.

&&

.MARINE...
Issued at 410 AM EDT Wed Sep 3 2025

Deepening low pressure over Lake Superior early this morning will
quickly lift northeast, reaching northern Ontario by late this
morning. The low is pulling a cold front through the lake early this
morning, resulting in southwesterly winds shifting north-
northwesterly to northwesterly (as can be seen on the 8z
observations). Behind the front today and tonight, cold air
advection and pressure rises will result in north-northwesterly to
northwesterly winds increasing to near 30 kts lakewide, with the
north central lake seeing solid gales to 35 kts until this evening
(a few gale force gusts to 35 kts are expected west of the Keweenaw
too, but I suspect that they won`t be as frequent). While many of
the CAMs aren`t showing high gale chances, given that this is a
setup where wind gusts often overachieve the max of model guidance,
went more with the traditional gust tool that mixed down much higher
winds than model guidance anticipates (NBM was the exception).
Therefore, a Gale Warning has been issued for the nearshore along
the northern shore of the tip of the Keweenaw, and for the open
waters north of it (and east of Isle Royale) as well. Given the
stronger winds and gusts expected from the previous forecast
package, significant wave heights are now projected to build to 5-
10ft north and east of the Keweenaw today. In addition to the winds,
given the strong temperature difference between the cold air aloft
and the relatively warm waters, as well as the low being overhead
today, some waterspouts are possible today through Thursday.

Winds become more westerly then southwesterly Thursday. Relaxing
pressure gradient and advection aloft will allow winds to fall to
near 20kts by Thursday night. These winds again increase Friday as a
clipper-like low presses quickly into Minnesota/Wisconsin Thursday
night. This low will reach northern Lake Michigan Friday morning
before entering Quebec Friday evening. Westerly to northwesterly
wind increasing to near 30kts is expected, with gales to 35 knots
having a 50 to 60% chance of occurrence according to the latest NBM
extended run. In addition, given how the low moves through Lake
Michigan, some waterspouts could return to the lake late Thursday
night and Friday over Lake Superior. Expecting winds to gradually
relax Saturday, then fall back below 20kts Sunday night. These
lighter winds hold into at least midweek next week.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Beach Hazards Statement from 10 AM EDT this morning through
     this evening for MIZ005-006.

  Beach Hazards Statement until 2 PM EDT this afternoon for
     MIZ014.

Lake Superior...
  Gale Warning until 8 PM EDT this evening for LSZ244-264.

Lake Michigan...
None.

&&

$$

SHORT TERM...TAP
LONG TERM...NL
AVIATION...TAP
MARINE...JTP/TAP