421
FXUS63 KDTX 111002
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
602 AM EDT Mon Aug 11 2025

.KEY MESSAGES...

- Warm and muggy conditions continue today through Tuesday with
highs in the low 90s and heating indices in the mid-90s.

- Potential for showers and non-severe thunderstorms from mid
afternoon into the evening hours today.

- Showers and thunderstorms again possible Tuesday, with the
potential for heavy rainfall.

- High pressure brings less humid conditions for the latter half of
the week.

&&

.AVIATION...

Predominately VFR conditions today with the possible exception of
later this afternoon/evening when a round of showers and
thunderstorms is expected to develop and drift east mainly between
20-00Z. Should have a quiet period until later overnight when the
low level jet flares up ahead of the cold front in the moisture rich
air. Could see a cluster of storms work northeast through the region
around 09-12Z for a few hours. Both periods offer better chances for
MBS/FNT/PTK but a chance farther south to Detroit as well. Being
toward the end of the taf period for most, held off on introducing
prob30 for the morning activity. Winds will be out of the south-
southwest around 10 knots with some gusts into the teens today.

For DTW/D21 Convection... There is a greater chance of thunderstorms
toward the northern reach of D21, lower toward DTW mid afternoon
into this evening. Second round of activity possible around 09-12Z
tonight into Tuesday morning.

THRESHOLD PROBABILITIES...

* Low for thunderstorms after 18Z Monday afternoon.

&&

.PREV DISCUSSION...
Issued at 352 AM EDT Mon Aug 11 2025

DISCUSSION...

Entrenched higher magnitude warmth with accompanying elevated
humidity will continue to mark conditions to start the work week.
Governing high amplitude ridging maintains control through at least
the first half of the daylight period today, with deeper layer
stability held under a warm mid level profile lacking in meaningful
thermal/moisture advection. This affords a similar outcome in
projected heat index, with afternoon readings again peaking in the
middle 90s. The ejection of a surface low into the northern great
lakes will combine with subtle height falls to draw a plume of
higher mid level theta-e attendant to a surface trough into the
region during peak heating. The improvement in 925-700 mb moisture
quality and subsequent destabilization beneath any lingering mid
level capping appears sufficient to support some degree of
convective development along the advancing convergence axis anytime
between mid afternoon and the evening hours. Convective depth muted
by paltry mid level lapse rates, while meager 0-6 km bulk shear will
keep any activity disorganized. Slow storm motion within a high pwat
environment offers localized heavy rainfall potential.

Southwest flow of greater depth will exist tonight and Tuesday. This
maintains potential for intervals of greater moisture advection to
occur at times, with a particular focus with nocturnal low level jet
development overnight and any less defined convectively enhanced
vorticity remnants traversing the mean flow. A virtually impossible
environment to offer any confidence in terms of timing, location and
coverage of convective development this period given the ill-defined
forcing field. Plausible the existing environment simply becomes
supportive of a more chaotic free convective release once daytime
heating finds an attainable mid 80s convective temperature. Forecast
will continue to highlight a scattered to numerous shower/storm
mention, targeting the Tue afternoon and evening window. Efficient
rate rate likely with any activity given the moisture quality, again
raising concern for some pockets of heavy rainfall.

A more dynamic mid level wave lifting across the northern great
lakes will shift a cold front across the region early Wednesday
morning. Secondary shorter window for convective development given
the increase in large scale forcing this period, but offset by a
noteworthy reduction in available instability at this stage,
particularly if earlier activity effectively stabilized the profile.
Temperatures then trending more seasonable with notably less
humidity for the late week period as Canadian high pressure takes
control.

MARINE...

Southwesterly winds persist today and Tuesday with a corridor of low-
end concern for isolated to scattered convective activity, mainly
for northern and central Lake Huron. Favorable marine conditions
persist for the rest of the central Great Lakes due to high pressure
anchored over The Southeast. A northern Great Lakes cold front will
take until midweek to clear through the region which eventually
offers chances for showers and thunderstorms across all the local
waterways. The front should exit Tuesday night, followed by a zonal
wind shift into Wednesday behind boundary which translates to drier
conditions.

HYDROLOGY...

Multiple rounds of showers and thunderstorms are possible this
afternoon through Tuesday ahead of a cold front that tracks through
the area Tuesday night. Moisture rich conditions are characterized
by PWAT values up to 2 inches and dewpoints in the low 70s.
Scattered thunderstorm activity will be capable of producing heavy
rainfall with rates over an inch per hour this afternoon and
evening. This will be followed by multiple potential waves of
thunderstorms Tuesday through Wednesday morning, in which slow-
moving and/or training thunderstorms will be possible. Flash
flooding will be possible in urban and low-lying areas along with
rises in areas rivers.

&&

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

$$

AVIATION.....DRK
DISCUSSION...MR
MARINE.......KGK
HYDROLOGY....MR


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