660
FXUS63 KDTX 110401
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1201 AM EDT Fri Jul 11 2025

.KEY MESSAGES...

- Trending warmer into the weekend, with heat index into the mid to
  upper 90s on Saturday.

- Increasing potential for showers and storms today and Saturday
  with isolated severe storms and heavy rainfall/localized flooding
  possible each day.

- Dry weather early next week with temps aoa 90 degrees on Tuesday.

&&

.AVIATION...

VFR skies carry through the majority of this morning with mainly
high clouds associated with upstream convective complex. That storm
system will be moving across Lower Michigan through the morning
hours possibly reaching southeast Michigan around mid to late
morning. There is moderate confidence that some activity may last
the journey into southeast Michigan, but less confidence in the
chance for thunder. Will maintain PROB30 for showers this morning
between 15-18Z. Renewed convective chances will quickly follow this
afternoon with a greater chance for scattered thunderstorms to
develop as instability increases.

For DTW/D21 Convection...Low chance for decaying thunderstorm
activity this morning between 15-18Z. Greater severe thunderstorm
potential will be mainly after 18Z.

THRESHOLD PROBABILITIES...

* Low for an isolated thunderstorm this morning. Medium for
  thunderstorms this afternoon.

&&

.PREV DISCUSSION...
Issued at 254 PM EDT Thu Jul 10 2025

DISCUSSION...

Morning fog and low clouds north of M-59 were slow to burn off, but
temps are quickly spiking toward 80 degrees, with mid 80s south of M-
59. Surface dew pts in the mid to upper 60s leading to MLcapes aoa
1000 J/kg over eastern Thumb region with weak low level
convergence/surface trough supporting isolated showers/thunderstorm.
However, mid levels are very dry, and surface dew pts will be mixing
down slightly late this afternoon, leading to diminishing instability
from west to east, ending any shower/thunderstorm threat very
shortly.

Multiple opportunities for showers and strong thunderstorms into the
Weekend, as the upper level wave/trough over Western Canada digs
southeast and swings through the Great Lakes region. Lead
upper level disturbances and deep/pseudo tropical moisture (PW of 2
inches/5+ C dew pts at 700 MB) over the Midwest/Central Plains will
be tracking off to the northeast tomorrow and Saturday through the
region, potentially in-sync with or close to the peak heating
of the day. If that is the case, at least a marginal risk of severe
weather exists with moderate instability, as MLcapes build
between 1500-2000 J/kg (per HRRR/RAP/NAM/RRFS blend) on Friday
(particularly along/west of U.S. 23) with precip loaded downbursts
possible, despite 0-6 KM bulk shear mostly in the 25-30 knot range.
Lead instability/moisture gradient arrives Friday morning (12-16z)
before more robust surge arrives late in the day. If showers and
possible embedded thunderstorms do in fact move in during the
morning from decaying MCS and do not dissipate in timely fashion,
previously mentioned capes and late day severe threat may
be hindered. However, better instability and shear over northern
Illinois may be able to develop another MCS, with organized system
still potentially able to support severe storms over southern
Lower Michigan early in the evening, and SPC has included parts of
the CWA in a slight chance of severe for this reason.

Even higher instability progged for Saturday as surface dew
pts push into the lower 70s, presenting an even better chance of
showers and strong to severe thunderstorms, especially if slightly
better wind fields arrive by 00z Sunday. This deep moisture and
relatively slow movement leads to a heavy rainfall/localized
flooding threat (both Friday and Saturday), especially in any urban
setting. With the higher dew pts and temps aoa 90 degrees on
Saturday (ultimately dependent on timing of convection), heat
indices may briefly rise into upper 90s/approach 100 degrees.

Upper level trough axis to swing through the Central Great Lakes on
Sunday. Enough low level moisture may still be around to touch
off scattered showers and thunderstorms as the 12z Euro shows
cold front slow to push east.

Upper level ridge (591-592 DAM at 500 MB) axis then builds over
the region early next, promoting dry but hot weather, with temps
likely aoa 90 on Tuesday.

MARINE...

High pressure to bring mostly dry conditions, outside of a low
chance for a stray shower, and calm to light winds through the day
today and into tomorrow.

Latest model trends now suggests a couple of possibilities for
showers and thunderstorm potential tomorrow. The first coming from a
decaying storm system that is expected to weaken as it travels into
the eastern Great Lakes tomorrow morning and afternoon. It is
possible some lingering thunderstorms can affect the region leading
into the afternoon hours. A secondary round of showers and
thunderstorms will then again move in from the western Great Lakes
with some development possible overhead, which brings the potential
to see strong to severe storms in the later afternoon and evening
hours. Small hail and wind gusts in excess of 40 knots will be the
main threats with any stronger storms. Additional shower and
thunderstorm chances will enter this weekend ahead of and along a
cold front.

HYDROLOGY...

The next period to monitor for potential heavy showers and storms is
Friday and Saturday as a hot and humid air mass builds back into the
region. The forecast for Friday carries a lot of uncertainty at this
stage, but there is the potential for a thunderstorm complex to
arrive from the west early in the day and act as a trigger for
afternoon showers and storms. If this occurs, the environment would
support heavy downpours with rainfall rates in excess of 1 inch per
hour and slow storm motions leading to localized flooding concerns.
Saturday presents a higher likelihood for showers and storms with a
similar environment also supportive of a localized flooding risk.

&&

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

$$

AVIATION.....AA
DISCUSSION...SF
MARINE.......AM
HYDROLOGY....SF


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