895
FXUS63 KDTX 120400
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1200 AM EDT Wed Aug 12 2026

.KEY MESSAGES...

- Isolated thunderstorms are possible through this afternoon and
evening with a low probability for severe weather and localized
heavy rainfall.

- The potential exists for showers and thunderstorms to develop both
Wednesday and Thursday.

- Drier conditions develop Friday through most of Saturday.

- Renewed chance of storms and potential for heavy rainfall by
Saturday night into Sunday.

&&

.AVIATION...

Calm wind environment with persistence of low to midlevel
deformation has led to invervals of MVFR ceilings across Southeast
Michigan this evening. Kept with the inherited br mention tonight
and low ceilings with peak August evapotranspiration and a calm
wind. Daytime heating and mixing should result in some boundary
layer cloud but kept clouds of below 5.0 kft agl at SCT. Increasing
anticyclonic flow late Wednesday will favor the development of a
backdoor cold front during the evening hours. Model signal currently
supports any increased probability for showers and thunderstorms to
remain north and east of the terminals across the Thumb.

D21/DTW Convection...No thunderstorm activity is anticipated during
the taf forecast period.

.DTW THRESHOLD PROBABILITIES...

* High for ceiling 5000 feet or less this morning.

&&

.PREV DISCUSSION...
Issued at 346 PM EDT Tue Aug 11 2026

DISCUSSION...

Fast west-northwest upper flow remains directed across the Great
Lakes tonight through Thursday as the synoptic pattern holds
relatively stagnant over much of the continent. This maintains a
modestly unstable environment with periodic chances for shower and
thunderstorm activity each day, but details on timing and placement
will continue to be governed by smaller scale perturbations within
the upper flow. Thus, this part of the forecast continues to carry
relatively low confidence for the local area. The greater threat of
severe weather and heavy rainfall will continue to be favored over
the Ohio Valley through midweek.

For the near term, a mature MCV is driving decaying convection
across northern OH along a CAPE gradient reinforced by remnant
outflow from a morning MCS. The orientation of this gradient and
Corfidi vectors favor further ESE propagation to continue along this
corridor to our south. The northern edge of remnant convection is
curling across areas south of I-94 with an isolated threat of a
gusty winds to 40 mph and localized heavier rainfall, but this
threat is rapidly sinking south of the border. Otherwise, stratiform
rain passes across areas south of I-96 over the next few hours with
upstream observations indicating potential for a few embedded
lightning strikes.

After the MCS departs, outflow on the northern flank meets a diffuse
stationary front positioned across southern lower MI and may provide
the trigger for additional isolated to widely scattered smaller
scale and disorganized convection south of I-69 the rest of the
afternoon. The thick cirrus shield associated with the MCS has
dampened afternoon destabilization, but latest mesoanalysis
advertises 500 to 1000 J/kg of MLCAPE given sfc dew points in the
lower 70s and mid-level lapse rates of 6.5 to 7 C/km. The main
window for convection will be through about 8pm with any lingering
activity tapering off by 10pm. Included a patchy fog mention tonight
as the front lingers in the area with higher humidity and clearing
skies.

Subtle height falls on Wednesday cause a weak surface
trough/convergence axis to sink south from northern Lower into the
Saginaw Valley and Thumb vicinity during the afternoon. This may be
enough to trigger convection, and with the active jet overhead there
will be a threat for isolated strong to severe wind or hail as well
as a localized downpour. Hi-res ML guidance favors a window between
3pm and 9pm for any stronger convection. The favored area for
convection on Thursday looks to again set up south of the area
toward the Ohio Valley.

By late Thursday into Friday, the large scale pattern will begin to
evolve with the western CONUS ridge amplifying over the Rockies.
Surface high pressure builds across northern Ontario on Friday then
migrates south into the Great Lakes to provide more tranquil and
slightly cooler weather through most of Saturday. This is followed
by a more potent system set to track across the Great Lakes on
Sunday. Its warm front arrives late Saturday, bringing a chance of
showers and storms by late evening. Ensemble QPF output indicates a
threat for heavy rainfall somewhere in the vicinity - 13Z NBM
advertises 30% for over 1 inch for parts of Lower MI by 00z Mon.

MARINE...

Weak wind fields will remain in place through Thursday as a frontal
boundary hangs around the Great Lakes region before dropping south
Thursday night. Periodic chances of showers and thunderstorms will
persist through that timeframe. Any strong thunderstorms will have
the potential to produce hail and winds in excess of 35 knots. With
the lighter winds, there are some weak signals for patchy dense fog
over Lake Huron at times, through confidence remains low.

A large area of high pressure builds into northern Ontario Thursday
night, allowing north-northeast winds to increase on Friday. Winds
are expected to reach at least 20 knots over southern Lake Huron,
which may allow waves to approach 4 feet over the southern basin.
The ridge extending from the high slides through Friday evening,
supporting lighter winds into Saturday morning. Southerly winds will
then peak out around 20 knots ahead of a cold front Saturday night,
with winds shifting to west on Sunday behind the front.

HYDROLOGY...

Slow-moving thunderstorms embedded within a broader area of light
rain will continue across areas south of I-94 through 5pm, bringing
a threat for localized heavy rainfall in excess of 1 inch.
Additional isolated thunderstorms are possible to develop this
afternoon and evening, mainly south of I-69. These storms would also
be slow-moving and pose a threat of localized heavy rainfall and
isolated totals up to around 1 inch. Minor flooding in urban and poor
drainage areas is possible through this evening.

&&

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

$$

AVIATION.....CB
DISCUSSION...TF
MARINE.......SF
HYDROLOGY....TF


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