629
FXUS63 KDTX 240958
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
558 AM EDT Tue Jun 24 2025

.KEY MESSAGES...

- Extreme heat warnings and advisories remain in effect today along
and south of the I-69 corridor.

- Scattered to numerous thunderstorms are forecast this afternoon
and evening. Locally strong winds and torrential rain will be
possible with these storms.

- Additional chances for thunderstorms will persist Wednesday
through Friday. Heavy rain will remain a risk through the end of the
week.

&&

.AVIATION...

We`ll reside on the edge of the strong ridge today with a cold front
dropping southward toward the area this morning. The front will
eventually pass through the area and settle near the Ohio border
tonight. The front should touch off a period of scattered to
numerous thunderstorms this afternoon/evening during peak heating.
Guidance also advertises a period of MVFR/IFR cigs tonight in the
wake of the front. Judging by upstream obs tonight, MVFR looks more
likely and will lean that way. Winds will start off southwesterly
but will flip around to the northeast tonight. Showers could
continue into/through the overnight but low confidence in coverage
and timing.

For DTW/D21 Convection...The potential exists for thunderstorms
today between 20z-23z. Locally heavy rainfall will be possible.
Additional showers will be possible through the night.

 THRESHOLD PROBABILITIES...

* Low for thunderstorms Tuesday 20z-23z.

&&

.PREV DISCUSSION...
Issued at 326 AM EDT Tue Jun 24 2025

DISCUSSION...

There will be a southward suppression of the strong mid level ridge
over the eastern US today as several short wave impulses track
across the northern Great Lakes. This will drive a slow moving cold
front southward into the forecast area during the day, expected to
reach the Saginaw Bay and thumb early this afternoon before sliding
southward into metro Detroit this evening. The flattening of the mid
level ridge will result in slight cooling in the mid levels over
southern Michigan, eroding the capping inversion. Diurnal
destabilization within the warm and humid airmass and convergence
along the cold front will support convective development this
afternoon and evening, with convective outflow convergence favorable
to multicell clusters. 0-6km bulk shear values are only forecast
around 15 to 25 knots over most of the area. SB CAPE values are
forecast to possibly exceed 2k J/kg depending on timing of convective
initiation, with good low level lapse rates and CAPE density. This
suggests a chance for strong/damaging winds due to wet micro bursts.
Moisture content will also be quite good with the depth of the warm
cloud layer around 15k feet and precipitable water values of 1.8 to 2
inches. Intense rainfall rates will be likely with any convection.
While this may lead to some localized flooding in urban Detroit, the
uncertainty in the coverage of convection is too high for any type of
flood watch issuance.

Timing of convective initiation will also play a factor into
afternoon high temperatures. Moisture pooling along the frontal
boundary will support dewpoints in the low 70s, which will result in
high heat indices again assuming highs are able to reach the low to
mid 90s. Due to the expected earlier timing of the front, the Saginaw
Valley and thumb region will likely top out with highs in the 80s.
Therefore, the heat headlines will be cancelled in this region but
will remain in place for the I-69 corridor south. If convective
development occurs a little earlier in the afternoon, these headlines
may be able to be cancelled earlier.

There is reasonable model agreement indicating the sfc cold front
will be south of the forecast area by Wednesday. This will support
cooler temperatures. An axis of deep layer moisture will however
remain across southern Michigan, keeping conditions rather humid.
There is the potential for the gradient in elevated instability to
reside across the far southern portion of the state. This will
warrant continued chances for convection dependent upon any short
wave features rippling across the westerly flow overhead, along the
northern edge of the elongated ridge. While still somewhat subtle,
there is some model support suggesting a little more backed flow
potential on Thursday which may drive the front north as a warm
front. This has the potential to drive the surface based instability
back into Se Mi, thus sustaining a chance of convection. The
potential for MCS development across the upper Midwest and western
Great Lakes region leads to a lot of uncertainty in the details of
convective chances/timing and its influence on temperatures through
the end of the work week. The persistence of the tropical airmass
overhead does however suggest a continued risk of intense rainfall
rates with localized flooding possible with any organized convective
systems.

MARINE...

A cold front gradually settles into the Great Lakes region today,
washing out overhead. This causes a shift in surface winds from
organized southwest flow to a more variable northerly flow pattern
by this evening. High pressure builds over Lake Superior tonight
which reinforces the northerly wind component through mid-week. Main
marine impacts will come from thunderstorm activity that redevelops
this afternoon and evening. Low predictability in exactly when/where
these storms will pop up given the numerous boundaries that will
exist this afternoon. The strongest storms will be capable of wind
gusts in excess of 34 knots and large hail. Despite high pressure
building in on Wednesday, thunderstorm chances remain in the
forecast through the end of the week as disturbances track along the
ridge axis that holds firmly in place over the southeast CONUS.

HYDROLOGY...

A slow moving cold front combined with a moist and unstable
atmosphere will trigger scattered to numerous thunderstorms across
much of the area this afternoon and evening. Very high atmospheric
moisture will result in intense rainfall rates, likely in excess of
an inch per hour at times. This may result in some urban and low
lying flooding. The uncertainty in convective coverage precludes the
issuance of a flood watch this morning. A plume of tropical moisture
will remain across southern Michigan through the end of the week.
This will result in an extended period with a chance of
thunderstorms capable of producing locally heavy rain.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Heat Advisory until 8 PM EDT this evening for MIZ060-062-063-068-
     075-082-083.

Lake Huron...None.
Lake St Clair...None.
Michigan waters of Lake Erie...None.
&&

$$

AVIATION.....DRK
DISCUSSION...SC
MARINE.......MV
HYDROLOGY....SC


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at www.weather.gov/detroit.