901
FXUS63 KDTX 160400
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1200 AM EDT Sun Aug 16 2026

.KEY MESSAGES...

- Gradually increasing chances for showers and possibly some
thunderstorms through tomorrow. Heavy rainfall leading to localized
flooding is possible, mainly along and south of the I-94 corridor.

- Showers and storm chances late Tuesday into early Wednesday.

&&

.AVIATION...

Smaller scale deformation forcing and broader 875-700mb thetae
advection attempted to bring shower activity to Southeast Michigan
for a period this evening. Uncertainty does continue to exist for any
coverage and duration of shower activity now that a little deeper
moisture is in place. Will need to monitor for the potenital of IFR
ceilings to develop overnight with weak flow. Additional activity is
forecasted to develop on nose of 850mb jet impulse back across
northern Illinois tonight and will brush Southeast Michigan sometime
between 10-14z Sunday morning. The potential does exist for some
intermittent shower activity at DTW during that timeframe but very
low confidence exists. Quiet period midday Sunday with another chance
of shower and isolated thunderstorm in southwest flow and along a
cold front 21z Sun to 6z Monday.

D21/DTW Convection... No thunder activity anticipated at the
airfield tonight. Additional window for convection is possible
Sunday morning 10-15z and again 21z Sun-06z Mon, but overall thunder
coverage is expected to be limited.

.DTW THRESHOLD PROBABILITIES...

* High for ceiling 5000 feet or less tonight and tomorrow.

* Low for thunderstorms this evening and again Sunday.

&&

.PREV DISCUSSION...
Issued at 301 PM EDT Sat Aug 15 2026

DISCUSSION...

Cloud shield has overspread a good portion of Southeast Michigan
today.  The clouds originated with yet another episode of deep
convection across Illinois and Indiana this morning.  The persistent
ribbon of deep moisture and reduced moist stability continues to
lurk just to the south with peripheral influence in the form of a
gradual increase in near surface moisture and expanding cloud cover.
Meanwhile, the warmest conditions are observed across the Thumb and
Saginaw Valley, where sunny skies remain.

A weak zone of stretching deformation below 700-mb is draped along
the southern border counties.  It is currently supported by
unbalanced flow through increasing system-relative cyclonic flow and
is maintaining forcing for light shower development, which is
expected to continue through the balance of the daylight hours.
Furthermore, a weak MCV just south of Lake Michigan will move
eastward along this zone - potentially augmenting the ongoing
activity into this evening.  The response will be muted in
intensity, though, due to the lack of instability.

Looking upstream, a shortwave trough over Montana and the southern
Prairie provinces will slide toward the region tonight. As this wave
approaches, it will start to interact with low-level frontal zone
across the corn belt.  One result will be the southwestward
extension of the upper-jet and the induction of below entrance
region ascent.  Coincidentally, the moist unstable airmass over the
mid-Mississippi Valley will claw northeast across the Lower
Peninsula tomorrow morning in a corridor ahead of the wave and the
approaching cold front.  Some residual upstream shower activity may
survive along the leading instability gradient as it advects into
Southeast Michigan during the early to mid morning.  Otherwise,
scattered showers and thunderstorms will develop across Lower
Michigan tomorrow afternoon into the evening. The best support for
coverage will be closer to the main shortwave across central Lower
Michigan into the Thumb region. Instability source depth will be
restricted to the lowest 1-km, with not much CAPE depth to govern a
higher predictability zone for sustained development. Furthermore,
the lack of deep layer shear projects the lack of convective
organization - aside from any activity that is forced along cold
frontal zone.

In the wake of the cold front, Monday and the first half Tuesday
look quiet and seasonable.

A broad region of height falls is expected across eastern Canada
into the Lakes region and the northeast going into midweek. All the
global ensemble families are trending toward lower with height
projections in the context of reduced intra-family spread - garnering
greater confidence in a meaningful pattern shift.  The onset of the
cooler conditions will be prefaced by a cold front with some showers
and storms possibly as early as Tuesday afternoon.  Chances are
lingering into early Wednesday, as the timing of the front is still
getting sorted out.  An early arrival would offer greater
thunderstorm chances during peak heating hours on Tuesday, while a
delayed arrival would place the region in the nocturnal minima for
convection.  The replacement airmass will be cooler and drier with
highs in the 70s and dewpoints in the low-mid 50s.

MARINE...

High pressure over the Northeast continues to move east over the
Atlantic as low pressure tracks across Ontario through Sunday. As
the low tracks north of the area, it will push a cold front through
the central great lakes region late Sunday. Ahead of the front,
south winds prevail for much of Sunday around 10 to 20 knots. Behind
the cold front, northwest winds fill in and increase across Lake
Huron, and eventually down through Lake St. Clair and the Michigan
waters of Lake Erie late Sunday. While the strongest winds are
expected across Lake Huron, especially the Open Waters with 20-25
knot winds expected Sunday evening into early Monday morning, will
need to keep an eye on the wave forecast and the potential for Small
Craft Advisories for nearshore waters across the tip of the Thumb of
Michigan. Showers and thunderstorms will be possible as this system
moves through Sunday and Sunday night. The best chance for
thunderstorms will be along the cold front later in the day and into
the evening hours.

&&

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

$$

AVIATION.....CB
DISCUSSION...Mann
MARINE.......JA


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