423
FXUS63 KMQT 220018
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
818 PM EDT Thu Aug 21 2025

.KEY MESSAGES...

- Dry weather is expected through this evening before the next
  chances of showers and thunderstorms return to the UP Friday.
  There is currently a Marginal Risk (level 1 of 5) for severe
  weather.

- A seasonably strong system moving north of the Great Lakes
  will bring hazardous marine conditions to Lake Superior this
  weekend; gales up to 35 knots are possible (30 to 40% chance).

- Cooler than normal temperatures and lake enhanced to lake
  effect rain showers are projected to return this weekend.

&&

.SHORT TERM /THROUGH FRIDAY NIGHT/...
Issued at 313 PM EDT Thu Aug 21 2025

Satellite imagery shows diurnal cu dotting most of the U.P.
landscape early this afternoon as high pressure continues to meander
its way southwards the rest of today into Friday morning. As it does
so, winds so far today have been fairly light and variable; given
the warm lake and near-normal temperatures being realized across the
area, the lake breezes off of the Great Lakes have struggled to
really push all that far inland. However, as troughing increases
with time from the northwest the rest of today to Friday as a system
moves from northern Manitoba to northern Ontario, expect southerly
downslope winds to begin picking up during the overnight hours as
slight warm air advection works into the region ahead of the system.
With warmer and more moist air working into the region the rest of
today through tonight, expect the cloud cover to increase late
tonight after the diurnal cu erodes away this evening; thus, we can
expect lows tonight to be a bit warmer than last, getting only down
to around 60 tonight instead of the 50s and 40s in spots (as was
seen this morning).

Rain chances begin to move into the western U.P. on Friday as
moisture-rich air continues to advect into the region and a weak
shortwave influenced by the more northerly system flies through
Upper Michigan. While it`s expected that this will bring rain
showers and thunderstorms back across the area Friday and Friday
night (mainly beginning in the afternoon according to the latest
CAMs), a `sneaky` stronger thunderstorm or two could bring some
gusty winds and small hail to the surface. However, with tall,
skinny CAPE and an unimpressive hodograph expected within the model
soundings, chances for marginally severe hail and winds look to be
rather slim (~5%). We can expect Friday to feel warmer though as
temperatures could squeak to around 80 along the downslopes by Lake
Superior and in the central and eastern U.P. As the rain chances
exit to our east Friday night, clearing skies behind the convection
are expected to help lows drop back down into the 50s across most of
the area.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Issued at 345 PM EDT Thu Aug 21 2025

The long term period starts out fairly interesting as cold air
advection associated with a system moving from northern Ontario into
northern Quebec this weekend into early next week is projected to
bring early Fall-like conditions to the U.P. throughout the weekend
into next Monday. With 850mb temperatures progressively lowering
down to as low as 3C between Saturday morning and Sunday night,
given that the latest Lake Superior surface temperature analysis
from GLERL shows temperatures in the mid teens to around 20C, we can
expect lake enhanced rainfall to develop over the northwest wind
belts, eventually transitioning to pure lake effect rain by late
this weekend into early next week as delta Ts drop into the mid
teens. The increase in near-surface instability could make things
rather breezy for the Keweenaw on Saturday, with winds potentially
gusting above 30 mph throughout the day. With the European ensemble
highlighting the anomalously cold air aloft and low-level clouds
expected to develop from Lake Superior, expect the warmest
temperatures probably near the Great Lakes this weekend into early
next week; highs are expected to only get to mid 60s to lower 70s on
Saturday before plunging down to around 60 Sunday and Monday. As for
the lows, while the expected low-level cloud cover should help
insulate things, given the cold air advection getting into the area,
expect temperatures to progressively drop into the 40s through this
weekend to early next week; we may even see low even into the 30s by
Monday night/early Tuesday morning as the cloud cover clears out and
the lake effect rainfall ends.

While we should warm a bit closer to normal for middle to end of
next week, with high pressure blocking dominating the western half
of North America next week, we are expected to remain within the
influence of the cooler air brought about by a synoptic-scale low
that looks to set up shop by Hudson Bay/northern Quebec.
Nevertheless, we can expect highs to progressively rise from the 60s
into the lower 70s as we head into the end of the work week.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 818 PM EDT Thu Aug 21 2025

VFR conditions will prevail through tomorrow morning and even then
will likely be the predominant flight category for most of the TAF
period. However, will carry PROB30 groups at all TAF sites by mid-
morning tomorrow for a 10-20% chance of thunderstorms, increasing to
60% by the afternoon as a shortwave traverses Upper Michigan. So,
there could be brief deterioration at times to MVFR/IFR levels in
any heavy downpours/thunderstorms that do form. In addition,
westerly winds will be strong at CMX with sustained speeds up to 15
kts, gusting to 20 to 25 kts.

&&

.MARINE...
Issued at 345 PM EDT Thu Aug 21 2025

Fairly light and variable winds this afternoon give way to southwest
to westerly winds up to around 20 knots Friday over the western lake
between the Keweenaw and Isle Royale as a frontal boundary pushes
eastwards across the lake. This boundary could bring showers and
storms across the western lake tonight and is expected to bring
additional convection across the entire lake Friday and Friday
night, with some of the storms potentially bringing gusty, erratic
winds and small hail to the sfc.

As cold air advection behind a low pressure system moving eastwards
from northern Ontario to northern Quebec moves across the area this
weekend, expect the winds across Lake Superior to pick up, with west
to northwesterly gusts of 20 to 30 knots expected across the lake on
Saturday (highest along the northern shore of the Keweenaw); there
is even a 30 to 40% chance according to the LREF and NBM that gales
to 35 knots will be realized as well late Saturday afternoon. While
no gale products have been issued yet due to the probabilities being
too low at this time, we are continuing to monitor the situation as
it evolves; stay tuned to the marine forecast for the latest
details!

With cold air advection still cycling across the region the rest of
the weekend into early next week, west to northwesterly winds to 25
to 30 knots are still expected to continue across the lake, with
decreased chances of low-end (35 knots or so) gales still being
highlighted. However, as ridging builds back into the Upper Great
Lakes Monday night into Tuesday, expect the winds to begin dying
down once again, becoming 20 knots or less again late Monday night
and remaining that way until the middle of next week.

&&

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

&&

$$

SHORT TERM...TAP
LONG TERM...TAP
AVIATION...TDUD
MARINE...TAP