878
FXUS63 KMQT 101800
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
200 PM EDT Sun Aug 10 2025

.KEY MESSAGES...

- Chances of showers and thunderstorms linger through Tuesday.

- High temperatures remain above-normal to near-normal
  throughout the next week.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 405 AM EDT Sun Aug 10 2025

Early morning RAP analysis and GOES Satellite imagery reveal a
closed upper low sitting just north of the Minnesota international
border with its surface pressure reflection underneath around
1006mb, extending a weak sfc trough across the Upper Midwest. Closer
to home, a weak perturbation in the longwave troughing is firing off
convection across s-central Lake Michigan. With the main forcing
displaced away from the UP, mostly clear skies are overhead save for
some anvil cirrus pushing northward. Temps have cooled into the 60s
area wide and patchy fog has been observed in the s-central where
recent rainfall has wet soils.

Through today, the aforementioned closed low to our N begins to
transition to an open wave as it reaches James Bay. The broad SW
flow extending across the Midwest and Northern Great Lakes will
allow for another warm and humid day. Though not as hot, daytime
temps pushing the low to mid 80s combined with upper 60s to near 70
degree dewpoints should create relatively uncomfortable muggy
conditions. The main forecast challenge for today aims to be
scattered showers and thunderstorms developing this afternoon across
the UP provided by weak synoptic lift via a subtle embedded
shortwave within broad troughing extending from the Plains.
Diurnally building instability should be sufficient for
thunderstorms with the HREF probability for 1000 j/kg of SBCAPE
reaching 60-70% between 18-21z. Bulk shear values 25-35 kts and
mostly straight hodographs suggest some gusty small hail producing
storms are possible in the strongest updrafts. The lack of strong
forcing, however, gives low confidence to anything reaching severe
intensity. Additionally, cant rule out the heavy rainfall potential
in strong storms with PWATs >1.5" and warm cloud layer depths exceed
10k ft. Recent rainfall and saturated soils may contribute to
localized ponding/flooding where the heaviest rainfall occurs. CAMs
are in fair agreement on a round of scattered convection pushing N-
NE into the s-central UP this afternoon and a second slug reaching
the western UP along a subtle cold frontal boundary in the evening.
As diurnal instability wanes with sunset and the main synoptic
forcing departs NE, would expect precipitation to diminish into the
overnight hours, though some CAMs hold onto precip in the eastern
UP. Otherwise, temps once again cool to the 60s area wide into
Monday morning.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Issued at 239 PM EDT Sat Aug 9 2025

By 00Z Monday, the cutoff low forcing this period of disturbed
weather will have weakened significantly as it lifts into the
Hudson Bay area. Longwave troughing will keep warm, moist air
over the area and thus keeping high temperatures Monday in the
low 80s despite falling 500mb heights with longwave troughing
extends from the Rockies into the Great Lakes. Remnant surface
troughing will keep PoPs in the forecast for Monday in the east
half, though the chances of rainfall rates over a quarter inch
per 6 hours is only around 15 percent per the LREF.

Attention turns to a shortwave trough rapidly moving southeast from
the Northwest Territories at 00Z Monday to just northwest of
the Upper Great Lakes basin by 18Z Tuesday. The last 24 hours of
ensemble guidance have granted much improved agreement on the
placement of the parent trough, though the resulting surface low
will be far enough north that precipitation over the UP may
need a boost from diurnal instability or perhaps a lake breeze
boundary. Instability looks ok, around 500 J/kg, and while bulk
sfc-500mb shear values around 40 kt look impressive, hodographs
look unidirectional for the most part. Winds aloft shifting out
of the northwest will be a little late to provide much relief
from above average temperatures as Tuesday`s highs will be
around 80 per the NBM, though overnight lows in the mid 50s in
the interior will be a welcome return to near-normal for this
time of year.

Quasi-zonal flow aloft is then expected for the midweek period,
keeping primarily dry weather in the forecast with near- to slightly
above-normal temperatures, though this pattern may allow for some
lake breeze showers if the conditions line up correctly. Model
spread then increases for the Friday and beyond period as the
various global deterministic and ensemble suites disagree on the
breakdown of southern US ridging and the arrival of a cutoff low
over the Canadian Prairie. Lots of variance in the resulting weather
is seen in the ensembles, though on a conceptual level, warm
southwesterly flow seems probable to return with chances of showers
and thunderstorms probably dependent on upstream convective
development over the Upper Midwest.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 200 PM EDT Sun Aug 10 2025

Lingering IFR/MVFR cigs this afternoon at IWD/SAW will lift to VFR
by this evening with VFR conditions then persisting the remainder of
the period, save for BR/FG at SAW tonight. CMX likely will remain
VFR the entire duration of the 18Z TAF period. Scattered SHRA/TSRA
are expected across the UP this afternoon and evening, but
confidence in timing and coverage impacting sites is not high.
Removed TSRA altogether from SAW and refined PROB30 groups at
IWD/CMX. Otherwise S winds around 10-12 kts this afternoon gradually
taper off into tonight.

&&

.MARINE...
Issued at 405 AM EDT Sun Aug 10 2025

Breezy southerly flow will keep afternoon gusts 15-20 kts in the
forecast through today, calming below 15 kts during the overnight
hours into the work week. Thunderstorms pressing N-NE this afternoon
and evening may cause gusty and erratic winds, primarily over the
eastern half of the lake. A strong shortwave passing through the
Northern Great Lakes Tuesday looks to increase SW winds upwards of
25 kts funneling between Isle Royale and the Keweenaw, elsewhere 20
kts or less.

&&

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

&&

$$

SHORT TERM...BW
LONG TERM...GS
AVIATION...Jablonski
MARINE...BW