119
FXUS63 KDTX 251034
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
634 AM EDT Sat Jul 25 2026

.KEY MESSAGES...

- Dry conditions with near normal temperatures are expected today.

- Heat and humidity build back into the region Sunday-Monday with
highs around 90 degrees and heat indices in the low to mid 90s.

- Isolated strong to severe thunderstorms Sunday, with a more
organized severe weather threat arriving Monday. Damaging winds are
the primary hazard both days.

&&

.AVIATION...

Residual dry and stable air associated with sfc high pressure
departing the eastern Great Lakes will maintain continued dry
conditions today. Aside from occasional mid/high level clouds,
diurnal mixing will result in a scattered diurnal cu field, based
around 5000 feet. Return flow associated with the sfc high will
result in light SSW winds during the afternoon.

D21/DTW Convection...No thunderstorms forecast today and tonight.

.DTW THRESHOLD PROBABILITIES...

* None.

&&

.PREV DISCUSSION...
Issued at 338 AM EDT Sat Jul 25 2026

DISCUSSION...

The 00z.KDTX RAOB sampled a very dry airmass last night, with PWAT
of 0.61" falling in the 10th percentile of daily sounding
climatology. The dry column is still in place this morning, with
mostly clear conditions observed via satellite across Lower
Michigan. Intervals of cloud anchored to a shortwave over the Upper
Midwest will begin to work across Lower Michigan around mid-day,
although not expecting any precipitation given how dry the resident
airmass is. The wave combined with a shift to southwest flow signals
the pattern shift on tap for Sunday-Monday, with just one more day
of seasonable temperatures in the mid-80s before warm and humid
conditions arrive.

Main drivers of this pattern shift are the amplifying ridge sprawled
over western CONUS and a strong low over Hudson Bay. Placement of
these features puts the Great Lakes within the enhanced belt of NW
flow aloft and in the path of multiple embedded shortwaves over the
next couple of days. Arc of instability advects into SE Michigan
late tonight-Sunday coincident with the arrival of left exit region
dynamics, triggering shower/isolated thunderstorm chances as early
as Sunday morning across the Saginaw Valley/Thumb. The instability
plume then presumably expands into all of SE Michigan during the day
Sunday, with models signaling possible peak heating redevelopment
followed by MCS potential overnight-Monday morning. The enhanced NW
flow (35-45 knots at 500mb) will be supportive of organized
convection, but with low confidence in timing and coverage. SPC
SWODY2 Marginal Risk reflects the uncertainty in both scenarios,
where several models suggest a capping inversion is in place during
the afternoon and/or send the nocturnal MCS activity to our
south/west toward the instability bullseye. For any thunderstorms
that do overcome these barriers, main concerns will be damaging wind
and heavy rainfall.

The more organized severe weather potential still looks to be latter
half of Monday with the arrival of the surface low and cold front.
This is going to depend largely on how convection unfolds throughout
the day, and how much instability is available to be engaged by the
stronger forcing. Still looking at a lot of model variability for
Monday, including thunderstorm coverage, timing of the frontal
passage, etc. which makes it difficult to glean any meaningful
details from the global/regional models beyond a broad severe
weather threat. All modes of severe weather are possible including
heavy rain, although damaging wind is again the primary threat. The
latest SWODY3 puts all of Lower Michigan in a Slight Risk of severe
weather.

The other aspect of this airmass is the heat and humidity, in which
temperatures both Sunday and Monday climb toward 90 degrees. This
pushes heat indices into the low-mid 90s each afternoon, supported
by a humid airmass with dewpoints in the 70s. More seasonable
temperatures then return mid-week behind the frontal passage, with
drier weather also anticipated.

MARINE...

Influence of high pressure wanes over the course of today as it
moves more along the Atlantic coast and as low pressure organizes
over the Plains states and central Canada. Light southerly wind
between the systems pulls warmer air and greater instability into
the central Great Lakes leading to increasing thunderstorm activity
by Sunday, including the chance for a strong to severe storm Sunday
night. The primary low pressure system then tracks across the
northern Great Lakes during Monday. Thunderstorm activity continues
to increase coverage and intensity with this system, especially
along the trailing cold front that brings a chance of strong to
severe thunderstorms as it moves through the region. Outside of
storms, wind and waves are low until the northerly wind shift post
front late Monday night into Tuesday when speed has potential to
reach 25 knots over southern Lake Huron.

HYDROLOGY...

Several rounds of showers and thunderstorms are possible Sunday into
early next week. An increasingly humid and unstable airmass will
lead to rainfall rates over an inch per hour in some thunderstorms.
Recent dry weather and low soil saturation will help mitigate
widespread flooding concerns, although localized flash flooding of
low-lying, urban, and other flood-prone areas remains possible if
thunderstorms repeatedly impact the same locations.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...None.
Lake St Clair...None.
Michigan waters of Lake Erie...None.
&&

$$

AVIATION.....SC
DISCUSSION...MV
MARINE.......BT
HYDROLOGY....MV


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