569
FXUS63 KMQT 110814
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
414 AM EDT Fri Jul 11 2025

.KEY MESSAGES...

- Isolated to scattered showers and thunderstorms are possible this
afternoon and evening, mainly along the MI/WI state line.

- More showers and thunderstorms are expected Saturday. Some of
these storms may produce strong winds and heavy downpours.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 413 AM EDT Fri Jul 11 2025

Upper air pattern over the northern CONUS and southern tier of
Canada per RAP analysis consists of primarily zonal 500mb flow
interrupted by a shortwave trough extending from southern MN to
eastern Nebraska and deteriorating ridging over northern Ontario as
well as a trough over Saskatchewan. For now, weak high pressure is
prevailing in the sensible weather over the UP this morning with the
1014mb high centered over southern Ontario keeping weather dry this
morning, though some scattered clouds over various portions of the
UP and Lake Superior are showing signs of the subsidence weakening
in favor of the lift just upstream. A few patches of fog are seen on
various METAR reports but nothing with particular spatial or
temporal consistency thus far. A few spots in the east have already
fallen into the mid 50s for lows, though lows in the west half are
expected to remain in the 60s (with Ontonagon still at 68 at almost
08Z with light warming downslope flow off of the Porkies).

PoPs have taken a considerable trend downwards with respect to
today`s precipitation outlook. CAMs now show only sufficient
forcing for precipitation with the first upstream shortwave
remaining to the south of the UP with the exception of a couple
of CAMs showing some diurnal convection over the western UP and
another couple that show the southern and eastern UP getting a
glancing blow from precipitation late this evening (though most
of the other CAMs confine that wave of precipitation to the
Lower Peninsula). Thus, today looks to be another warm day
across the UP with warm southerly flow allowing highs to
continue to trend upwards, around the 80 degree mark. CAMs for
the most part do resolve another Lake Superior lake breeze,
though the background southerly flow will result in fairly
shallow inland penetration of such a breeze, perhaps around 5
miles.

Tonight, attention turns upstream to the aforementioned trough
currently over the Canadian Prairie as it approaches the Great Lakes
basin. The trough will support a weak surface low pressure, which
will lift a weak warm front towards the region around 12Z Saturday.
Of particular note however will be the cold front draped south of
the low, which the available CAM guidance shows approaching or being
over the western arm of Lake Superior by 12Z Saturday. Forcing looks
to be stronger with the cold front, so severe thunderstorms ahead of
its arrival are not expected, though Euro ensemble MUCAPE values
around 250 J/kg will be sufficient for a few rumbles of thunder
(conditional on the presence of showers). Another warm night is
expected with lows in the lower 60s expected.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
Issued at 207 PM EDT Thu Jul 10 2025

Beginning Saturday, phasing split flow over the Upper Great Lakes
with the passage of a cold front from west to east will result in
showers and thunderstorms moving through the forecast area for a
majority of the day. Increasing jet dynamics in the afternoon and
evening, alongside deep layer shear of 35-45kts and MUCAPE growing
potentially to 1000-1500j/kg should support upscale convective
growth ahead of the front, posing a strong to severe thunderstorm
risk. Location of this risk will depend on the rate of
destabilization ahead of the front through the day. However, with 12z
guidance leaning into the front pushing into the western counties
near 12z, suspect shower and thunderstorm activity may begin early
in the west, with strong to severe potential increasing by late
morning and early afternoon interior west and central, then peaking
in the mid afternoon and evening central and east. Mid-level lapse
rates near 6C/km and DCAPE ~1000j/kg suggest mainly a severe wind
risk, but should a stronger updraft get going, small hail can`t be
ruled out. Shower and storms may have difficulty moving off the
frontal boundary per MBE velocities, which with PWATs increasing to
near 1.5 inches, the warm cloud layer increasing to 10-12k feet, and
some guidance packages suggesting low corfidi vectors, heavy rain
will be possible should backbuilding or training occur. Right now
flash flood potential, per WPC, is marginal (5-14%), but
deterministic guidance suggests potential of 1 to 2 inches of QPF
will be possible for parts of central Upper Michigan. Shower and
thunderstorms looks to exit east near midnight, with surface ridging
building in afterwards. Should notable QPF occur Saturday with
enough dry air afterwards to support clear skies overnight,
overnight fog may develop.

The surface high will dip southeastward through the day Sunday while
maintaining ridging overhead. This keeps conditions mostly dry into
Monday, although a secondary shortwave within the broad transiting
trough may support an afternoon uptick in cloud cover, perhaps
diurnally enhanced. In the past 24 hours, guidance on the next
wave Monday into Monday night has trended more north, although
some deterministic guidance solutions continue to resolve
rain/storms. Further upstream, a deep trough and cold front
moving through the Canadian Prairies and a shortwave lifting
northeast from the Central Plains will shift toward Upper
Michigan on Monday. 6z Euro suggest the two features may remain
separate, while the GFS continues to suggest potential phasing
overhead in the Tuesday and or Wednesday period. Given this
uncertainty, confidence in the timing and position of when that
batch of precip occurs is low. Daytime highs each day look to
climb into the 70s to mid 80s. After next week`s cold front,
daytime highs look to climb only into the upper 60s to near 70.
Overnight lows are largely expected to be in the 50s and 60s,
with potential for may interior locations to cool into the low
to mid 40s behind next week`s front.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 149 AM EDT Fri Jul 11 2025

VFR conditions are expected at CMX/SAW through the duration of the
6Z TAF period while IWD likely lowers to MVFR early this morning for
FG/BR development. SHRA/TSRA look to return late Fri
afternoon/evening, continuing into Fri night at IWD/SAW. With precip
onset timing near the end of the period and still some spread yet in
guidance, opted to add a PROB30 group in at IWD, but left mention
out at SAW for now. CMX likely holds dry until Sat. Otherwise light
winds are expected with wind direction possibly impacted by a lake
breeze this afternoon.

&&

.MARINE...
Issued at 155 PM EDT Thu Jul 10 2025

Winds generally remain around 15 kts or less into the weekend with
the exception of some 15 to 20 kts over eastern portions of the
lake. By Saturday though, 15 to 20 kt winds out of the southwest
will become more widespread through Sunday before decreasing again
late Monday. This will coincide with some disturbances moving
through the Great Lakes Region over the weekend. With these
disturbances, showers and thunderstorms will overspread the lake
from west to east Friday through Saturday. Further out, additional
shower and thunderstorm chances will accompany a Clipper system late
Monday through Tuesday. Also of note, patchy fog could result in
reduced visibilities across far western portions of the lake
tonight.

&&

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

&&

$$

SHORT TERM...GS
LONG TERM...JTP
AVIATION...Jablonski
MARINE...TDUD