060
FXUS63 KDTX 221228 CCA
AFDDTX

Area Forecast Discussion...CORRECTED...
National Weather Service Detroit/Pontiac MI
445 AM EDT Tue Jul 22 2025

.KEY MESSAGES...

- Dry and seasonable temperatures today.

- Heat and humid increase Wednesday with heat indices in the
upper 80s to low 90s

- Thursday will be the hottest day of the week with heat indices
possibly exceeding 100F; some storms are also possible, especially
overnight.

- Warm and muggy conditions persist Friday with additional
shower/storm chances into the weekend.

&&

.AVIATION...

A warm advection pattern aloft brings in scattered/patches of mid
clouds (10-12 kft) today. Otherwise, low level moisture will be
lean, but may be enough to support a few VFR (4500-5000 ft) based
diurnal cu this afternoon. Clear skies expected this
evening/tonight. Very light easterly or variable winds will veer to
the southeast today, with a slight increase in speeds during the
afternoon due to diurnal mixing, but still under 10 knots.

For DTW/D21 Convection...No thunderstorms will occur through the TAF
period.

THRESHOLD PROBABILITIES...

* None.

&&

.PREV DISCUSSION...
Issued at 445 AM EDT Tue Jul 22 2025

DISCUSSION...

Surface high pressure slides into the eastern Great Lakes today
while the central CONUS ridge amplifies across the Midwest/Great
Lakes through mid-week and set the stage for a notable warming
trend. Surface winds will adjust accordingly this afternoon and
become southeasterly. These lower level wind fields offer one more
day of comfortable dewpoints that will be in the 50s today with most
locations seeing daytime highs in the upper 70s to low 80s. Deep
layer dry air and ridging will keep the weather dry today.

Thermal ridge folds into the central Great Lakes tomorrow with flow
becoming more south to southwest. This will usher in higher
dewpoints into the 60s and the warmer 850 mb temperatures to near
20C are drawn across southeast Michigan. A muggy day will be in
store with heat indices climbing into the upper 80s for most of
southeast Michigan and low 90s achievable across the Saginaw Valley.
Consensus is still to keep southeast Michigan free of precipitation
as shortwave energy directs convection to the north across northern
Michigan and/or northern Lower Michigan.

Thursday will be more than likely be the hottest and most humid day
of the week as 850mb temperatures climb above 20C. Latest guidance
is offering dewpoints into the mid 70s, which is possible, but tend
to be a little skeptical this far out to achieve these high of
dewpoints of 75 to 76 while also seeing high temperatures into the
mid 90s. If southeast Michigan in fact does see some of these high
dewpoints, then the high likely be more low 90s. Feel that lower 70s
dewpoints are more plausible, especially looking at current
observations across the lower Midwest. Another factor to watch out
for will be possible cloud cover nearby given the frontal features
to our north and the associated convection that could mess with high
temperatures. All that to say, outgoing forecast will continue to
highlight heat indices topping 100 degrees on Thursday, but below
the 105 degrees needed for Extreme Heat criteria. A heat advisory
will be needed if greater cloud cover and convection appears like it
will hold to the north through the bulk of the day.

Canadian troughing and shortwave features will work to flatten the
ridge into Thursday evening and overnight while supporting
convection along a south sagging boundary. This will bring the
highest chances for showers and thunderstorms after 8 pm on Thursday
and through Friday. MUCAPEs remain supportive of thunderstorms
through the overnight period with PWAT in the 1.75 to 2.00 inch
range supporting heavy rainfall potential. Only minor relief from
the heat and humidity on Friday with high temperatures holding in
the 80s. Zonal flow into the weekend will continue to offer an
unsettled pattern with shortwave features streaming in from the west
bringing additional chances for showers and thunderstorms into the
weekend.

MARINE...

Winds shift to the SE this morning as the center of high pressure
slides into Quebec though remaining light (less than 15kts). Low
pressure over the northern Plains then lifts a warm front through
the central Great Lakes Wednesday. Storm chances look to be confined
to the northern half of the Lake Huron Wednesday-Thursday owing to
closer proximity to the low. These chances then expand over the rest
of the region Thursday night through late week as the attendant cold
front sags through the Great Lakes.

&&

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

$$

AVIATION.....SF
DISCUSSION...AA
MARINE.......KDK


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at www.weather.gov/detroit.