330
FXUS63 KDTX 292330
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
730 PM EDT Mon Jun 29 2026

.KEY MESSAGES...

- Heat and humidity continue to build this afternoon leading to peak
heat index in the mid to upper 90s, especially for locations inland
from the lakes.

- An Extreme Heat Warning is now in effect Tuesday afternoon through
Thursday for high temperatures reaching the mid 90s to 100 degrees
and heat indices in excess of 105 degrees each day.

- There will be little nighttime relief as lows only cool into the
mid 70s with heat index around 80 each night.

- Wednesday and Thursday are the hottest days, however hot and humid
conditions also extend into Friday and the holiday weekend along
with increasing potential for showers and thunderstorms.

&&

.AVIATION...

Benign aviation conditions tonight with VFR mid/high cloud being
predominate and light south-southeast winds. Warm front stalled just
south of the state eventually lifts through Tuesday morning shifting
winds to the southwest. Breezy conditions expected through the day
with peak gusts around 25kts. Some diurnal is possible again but
skies remain VFR.

D21/DTW Convection... No thunderstorms are forecast for the D21
airspace through Tuesday night.

.DTW THRESHOLD PROBABILITIES...

* None

&&

.PREV DISCUSSION...
Issued at 353 PM EDT Mon Jun 29 2026

DISCUSSION...

Observations and the latest forecast data incoming today present no
big changes to the trajectory of heat building across SE Mi through
the mid week period. Today is the transition day as temperatures and
humidity make a notable jump from weekend conditions while also
buffered somewhat by the SE surface wind component and high clouds
from convection across the northern Great Lakes. Highs in the lower
90s with heat index rising into the mid to upper 90s remain in reach
this afternoon for interior locations while the clouds and SE wind
maintain a cooler profile toward the shorelines.

Heat building into the extreme range during Tuesday is primarily
driven by surface and low level wind veering SW in combination with
the slightly eastward shifting 594 dm 500 mb ridge. These larger
scale trends, also combined with deepening low pressure in central
Canada, draw the full Bermuda high air mass into southern Lower Mi
during the morning. Afternoon peak heating takes it from there for
highs in the mid to upper 90s combined with surface Td in the mid to
upper 70s yielding max heat index in the 105 to 110 range. Guidance
temperatures in today`s forecast package then identify Wednesday and
Thursday as the peak in this heat event, at least in terms of max
temperature. Both Wednesday and Thursday highs have a chance to
reach 100 and have a chance to break relatively low hanging DTW
record highs (ref Climate section below). Surface Td is projected to
drop off a few degrees but still maintain heat index in the 105 to
110 range followed by nighttime readings only dropping into the mid
and upper 70s with heat index around 80. Today`s upstream
observational evidence of these conditions across IL/IN and points
south/west, combined with the expected magnitude and duration of
this event, support the case for extreme heat and the upgrade from
Watch to Warning issued earlier this afternoon for the entire period
through Thursday.

Convective trends also demand forecast attention for both potential
coverage of cloud debris and eventually downstream MCS trajectories.
Low level jet supported activity last night into the still ongoing
storms this afternoon are closely following the customary leading
edge cap temperature of 10 C or warmer at 700 mb. This thermal ridge
builds even more strongly over Lower Mi tonight into a position to
support both peak surface temperatures and also direct new
convection to the north closer to the surface front through
Tuesday/Tuesday night. Cap predictability does drop off Wednesday as
700 mb temps moderate and the surface cold front reaches the Straits
region, however the larger scale pattern still favors storms holding
on a track across the northern Great Lakes through Thursday.

The ridge is further suppressed by the deamplifying northern stream
mid/upper level westerlies during Friday. This is the first sign of
heat dropping below peak, although the cold front is projected to
stall and wash out across the northern Great Lakes for no real
surface air mass change in SE Mi. The hazard potential of heat and
humidity for this time period will be evaluated/updated in upcoming
forecast cycles, however data appears to support at least some
relief below the warning threshold during the holiday weekend.

MARINE...

A warm front lifts across lower MI this evening and tonight.
Prevailing southeast wind on the order of 10 kt continues over the
central Great Lakes with gusts to around 20 kt over Lake Huron. The
front continues pushing northeast across Lake Huron on Tuesday with
wind gradually veering to southwest as much warmer and more humid
air builds into the area. The gradient will maintain SW wind of 10
to 15 kt Tuesday through Thursday, with gusts generally capped
around 20 kt due to increased stability from the hot air mass. There
will be a chance for thunderstorms over Lake Huron on Tuesday as the
front lifts through, but confidence is low on timing. Areas of fog
may develop over the cooler open waters as well. Additional storms
will be most likely to occur near northern Lake Huron where the
stability is weakest this week.

CLIMATE...

Daily Records for the Upcoming Week...

Detroit
                Record High       Record Warm Minimum
Mon June 29       96 (1933)            77 (1945)
Tue June 30       96 (1931)            76 (2018)
Wed July 1        98 (1931)            80 (1931)
Thu July 2        99 (2011)            76 (2018)
Fri July 3       100 (1911)            78 (1911)
Sat July 4       102 (2012)            79 (1921)

Flint
                Record High       Record Warm Minimum
Mon June 29      100 (1934)            75 (1945)
Tue June 30       98 (1933)            76 (2018)
Wed July 1       102 (1931)            72 (2018)
Thu July 2       100 (1931)            73 (2002)
Fri July 3        99 (1921)            73 (1983)
Sat July 4       102 (1921)            76 (1999)

Saginaw
                Record High       Record Warm Minimum
Mon June 29      100 (1971)            75 (1971)
Tue June 30       99 (1964)            77 (2018)
Wed July 1       103 (1931)            78 (1931)
Thu July 2       100 (1931)            73 (2002)
Fri July 3        99 (1966)            76 (1974)
Sat July 4        97 (2012)            75 (2012)

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Extreme Heat Warning from noon Tuesday to 8 PM EDT Thursday for
     MIZ047>049-053>055-060>063-068>070-075-076-082-083.

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

$$

AVIATION.....KDK
DISCUSSION...BT
MARINE.......TF
CLIMATE......MV


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