035
FXUS63 KMQT 020807
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
407 AM EDT Tue Sep 2 2025

.KEY MESSAGES...

- A cold front will move through the region tonight and
  Wednesday. This will bring widespread light to moderate rain
  to Upper Michigan and breezy winds in the Keweenaw.

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

- There is up to a 30% chance for northwest gales Wednesday into
  Wednesday night, mainly west and north of the Keweenaw
  Peninsula.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 406 AM EDT Tue Sep 2 2025

Remnant high pressure ridging over us early this morning is allowing
mostly clear skies to dominate, as well as letting temperatures drop
down into the 50s in the interior areas. However, expect cloud cover
to begin moving into the west this afternoon as a cold front drops
down from northern Ontario. As the front approaches, expect showers
and storms to develop over the U.P. late today through tonight,
beginning in the west. While there is around 1 kJ/kg of CAPE to work
with over the west by this afternoon, given the lack of wind shear
throughout the atmospheric profile, no severe weather is expected;
if any, expect the convection to be `popcorn`-like, coming up and
crashing down relatively quickly. As the convection continues to
move eastwards across the U.P. tonight, there looks to be a few
hundred J/kg of CAPE still above the nocturnal boundary layer across
the area, allowing low-end chances (30% or less) for thunderstorms
to continue through the overnight hours. As the cold front begins to
push into the west late tonight/early Wednesday morning, expect the
temperatures to begin dropping down to around 50F.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 406 AM EDT Tue Sep 2 2025

Late tonight/early Wednesday through Thursday morning, a cold front
sweeps over Lake Superior. While the surface low is expected to stay
to the north of the UP, the attendant cold front will march across
the area Wednesday, bringing with it widespread rainfall and a few
thunderstorms. The post-frontal winds will be worth watching
especially for interests on Lake Superior or near the lakeshores as
rapid height falls along with rapid pressure falls is generally a
good setup for winds to overperform model guidance, and the LREF
already has chances of gales around 20-40 percent. This forecast
will reflect sub-gale conditions in line with the NBM, though would
not be surprised if this climbed up more as more medium-range
guidance begins to model this regime.

The cool northwesterly flow and lowered heights behind the cold
front will lead to cool temperatures both at the surface (NBM
*highs* Thursday in the upper 40s in interior Marquette County) and
aloft, with the LREF showing 90+% chances of prolonged temperatures
below 3 C, which when compared to Lake Superior`s temperature being
around 16 C, leads to unstable enough conditions for lake enhanced
to lake effect precipitation. As the LREF still shows no surface
temperatures sub-freezing yet, this will fall as light rain.

A secondary trough will drop down from the Canadian Prairie into the
Midwest Friday through the weekend, eventually merging with the
aforementioned trough which will continue to wobble around northern
Ontario. This will bring another surge of yet-cooler temperatures,
with Sunday morning being the coolest morning of the forecast as NBM
lows fall into the mid-30s for the interior west. Should some breaks
in the lake-effect/enhanced precip and clouds occur, some frost is
possible, but with the uncertainty around the potentially insulating
cloud cover, will elect to keep just mentions of patches of frost at
this time. This trough will also bring chances of gusty
northwesterly winds potentially up to gale force (20% chance late
Friday) and rain (lake enhanced and lake effect). Following the
trough merger, troughing advances towards eastern Canada and the UP
finds itself upstream of central North American longwave ridging,
and the resulting surface high pressure eventually brings an end to
precipitation and slightly warmer temperatures by the late
weekend/early next week timeframe.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 129 AM EDT Tue Sep 2 2025

VFR conditions expected much of the 06z TAF period aside from patchy
fog at IWD/CMX. Any fog will burn off come sunrise. Otherwise,
increasing clouds (VFR) are expected today with breezy S-SW winds
upwards of 15 kts. A cold front will bring showers and thunderstorms
late in the period into the western UP. Guidance shows varying
degrees of coverage, including some possible prefrontal convection
this afternoon. Have generally timed out -shra/tsra at IWD and CMX
first with prob30 groups ~16-18z, then SAW later towards 20z.

&&

.MARINE...
Issued at 406 AM EDT Tue Sep 2 2025

Remnant high pressure ridging will keep winds at around 20 kts or
less today over the lake. Overnight into Wednesday, increasing
pressure gradient ahead of the next system will allow for increasing
southwesterly gusts across the eastern end of the lake to build up
to 20-25kts.

A cold front will then move move through the region late tonight
into Wednesday. Overall, the forecast represents southwesterly to
southerly winds to 20 kts ahead of the front and then increasing to
25 to 30kts from the north-northwest to northwest behind the front
(tonight and Wednesday). Differences in the exact setup of the
system continue to reduce confidence in gales, though this is a
setup that tends to outperform guidance. Currently, chances of gales
are about 15-35 percent, with localized gales potentially in the
Isle Royale vicinity Wednesday night. This front will also bring
with it 30-40 percent chances of thunderstorms and the gusty winds
behind the front will bring waves up to 6 ft.

For the late week period, as the main trough remains broadly over
northern Ontario, winds shifting to the west and southwest remain
around 20 kt, perhaps falling below 20 kt late Thursday into early
Friday. A secondary trough will merge with the first Friday into the
weekend, reinvigorating wind gusts into the 20s kt range with
another around 20 percent chance of gales Friday night. Northwest
winds remain gusty and waves increase to 5-7 ft Saturday before the
gusts fall below 20 kt by Sunday as the disturbance lifts out of the
area and high pressure establishes itself to end the weekend and
begin next week.

&&

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

&&

$$

SHORT TERM...TAP
LONG TERM...GS/TAP
AVIATION...BW
MARINE...GS/TAP