911
FXUS63 KDTX 052246
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
646 PM EDT Fri Sep 5 2025

.KEY MESSAGES...

- Cool this weekend with highs in the 60s and lows in the 40s.

- Isolated showers possible Saturday afternoon and Sunday.

&&

.AVIATION...

Standard loss of boundary layer depth with sunset will bring a
steady decline in gust frequency and magnitude this evening.
Lingering VFR cloud supported by diurnal processes will also fade
accordingly. Pocket of thicker cirrus will mark conditions for the
overnight period within a modest southwest gradient. Inbound mid
level wave pivoting through the broader upper level trough will
support an increasing coverage of lower VFR cloud late tonight and
into Saturday morning. Extensive VFR cloud solidified by daytime
heating for the afternoon and evening hours. Plausible for a few
inconsequential late day showers to materialize within this
environment. Occasional westerly gusts into the 20 knot range for
the afternoon.

THRESHOLD PROBABILITIES...

* Low for cigs 5000 feet or less Saturday

&&

.PREV DISCUSSION...
Issued at 329 PM EDT Fri Sep 5 2025

DISCUSSION...

Respectable low pressure sliding over the eastern UP has maintained
healthy wind gusts across SE MI so far today with most areas having
already seen frequent gusts between 30-40mph. Surface cold front is
in the process of clearing east of the region around time of
discussion ushering in another round of reinforcing CAA dropping
850mb temps to 3-4C by tonight continuing the pattern of overnight
lows in the 40s. Winds eventually slacken this evening as surface
low pressure quickly shifts into northern Quebec loosening the
gradient.

Upper trough settles over the Great Lakes this weekend keeping
temperatures a solid 10 degrees below normal as highs generally only
reach the mid 60s. Upper pattern allows a series of weak shortwaves
to traverse into the central Great Lakes offering lingering unsettled
weather. First of these waves swings out of the northern Plains over
the southern Great Lakes Saturday afternoon and is the weakest of
the two. System is fairly lean on accompanying moisture transport,
only a 0.1-0.3" increase in PW, however with lake temps still in the
60s, delta-t`s are more than sufficient for additional supplemental
moisture flux off the waters. This is likely the primary reason why
the coarser global models advertise little if any rain whereas high-
res solutions are able to generate isolated to scattered light
showers/drizzle latter half of the day. For now introduced slight
chance Pops (15-20%) across the vast majority of SE MI Saturday
afternoon-evening given the agreement across the higher res suite.

Second shortwave drops across the northern Great Lakes and across
the central portions of the lower peninsula Sunday morning. Track
supports a multi-lake connection between Superior and Michigan to
enhance accompanying shower activity. That said, northwesterly lower
level flow with the wave is an unfavorable direction to see this
moisture fully reach SE MI. This in addition to the main PV anomaly
tracking towards the Saginaw Bay results in better shower chances
(20-30%) being confined towards the Tri-Cities/Thumb.

Surface high pressure builds over the region by Monday as upper
troughing retracts towards Quebec. Moderation in temperatures each
day follows as highs return to the mid 70s by Tuesday with a shot to
see near 80 Wednesday ahead of the next approaching cold front. This
front currently looks to sag into southern MI more as a weak
backdoor cold front leading to a dry or mostly dry fropa.

MARINE...

The passage of the cold front this afternoon has veered the winds
more westerly but they remain at gale force mainly 35 to 40 knots
across most of Lake Huron and slightly lower around 25 to 30 knots
over Lake Erie and Lake St Clair. Headlines will remain through 10
pm with the expected decrease as we lose diurnal mixing processes
and the pressure gradient relaxes. We may need to transition from
the Gale Warning to Small Craft Advisory for Saginaw Bay  for the
rest of tonight as winds hover around 25 knots with waves around 4
feet for several more hours. The upper level trough will hold over
the region through the weekend with several weaker troughs/fronts
passing over. This will reinforce the cold airmass in place keeping
temps in the 60s this weekend. Waterspouts will be possible today
into this weekend with this colder air over the waters. Cooler,
unsettled weather lingers into early next week as the upper trough
settles over the Great Lakes.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Beach Hazards Statement until 10 PM EDT this evening for MIZ049-055-
     063-083.

Lake Huron...Gale Warning until 10 PM EDT this evening for LHZ361>363-421-422-
     441>443-462>464.

Lake St Clair...Small Craft Advisory until 10 PM EDT this evening for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory until 10 PM EDT this evening for LEZ444.

&&

$$

AVIATION.....MR
DISCUSSION...KDK
MARINE.......DRK


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