842
FXUS63 KDTX 090410
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1210 AM EDT Sat Aug 9 2025

.KEY MESSAGES...

- Hot and muggy weather builds in this weekend with heat index well
  into the 90s Saturday through Monday.

-Dry over the weekend, with a better chance of showers and
 thunderstorms returning early next week.

&&

.AVIATION...

Stable SW flow sets in late tonight and lasts through the day into
Saturday evening. This is ensured by a sharp 500 mb ridge that
supplies enough subsidence to suppress shower/storm development
across SE Mi. Storms that develop late tonight across the Midwest
are projected to approach central Lower Mi later Saturday evening
but remain west of MBS before dissipating. In between time,
conditions are VFR along the terminal corridor with the exception of
brief and shallow fog around sunrise followed by mixed coverage of
high clouds and shallow cumulus in the afternoon into Saturday
evening.

For DTW/D21 Convection... Thunderstorms are not expected late
tonight and Saturday.

THRESHOLD PROBABILITIES...

* None.

&&

.PREV DISCUSSION...
Issued at 326 PM EDT Fri Aug 8 2025

DISCUSSION...

Still expect some late afternoon and evening convection across
northeast Lower and then propagating down into the Saginaw Valley
and Thumb regions. While the hi-res models have been woeful in their
depiction of the Lake Huron MCS, they all show some thundestorms
development near the lake breeze with MLCAPES around 1500 J/kg and a
weaker cap. The outflow from the Lake Huron convection should only
enhance the low level convergence near the Lake Huron lake breeze.
With very little shear, expect little organization and slow moving
storms. The instability may be enough to have some pulse near
severe activity before the loss of the diurnal instability ends the
activity before or at midnight.

Other than some left over convective clouds tonight, not much else
to the night forecast. 500 mb heights build as the warmer and more
moist air continues to slowly advective in.  Low temps should be
several degrees warmer Saturday morning which is in line with
guidance temps.

That upper level ridge axis settles over Lower Michigan Saturday
before slowly moving east on Sunday. This will allow the slow
advection of the warmer and moist air mass. The cap strengthens with
warm 700 mb temp and nearly all of the guidance is dry for the
weekend for southeast Lower Michigan. The exception could be late
Sunday as the combination of being closer to the front with an old
outflow from upper/mid MS river valley MSC, and the Lake MI lake
breeze could develop some showers and storms over western Lower and
that could move into part of the DTX forecast area before
dissipating. Otherwise, expect mostly clear/sunny skies with high
temps in the lower 90s and heat indices touching the mid 90s with
dewpoints around 70. That is below Advisory levels, but the
consecutive days of hot days and warm nights may lead to some
consideration by Sunday and/or Monday.

The extended forecast hasn`t change much as the cold front that was
stalled over WI/IL will fold over Lower MI leading to better chances
of thunderstorms through the first half of the week. Then with weak
zonal flow for the later half of the week and some weak embedded
shortwaves, small chances of afternoon showers and storms for late
next week. Heat will remain over the region for Monday but with
increasing cloud cover, lower upper level heights, and periodic
convection, maxTs are more likely in the mid 80s.

MARINE...

Most imminent marine concern is a severe thunderstorm located
southeast of the Northern Lake Huron buoy, which is producing large
hail up to golf ball size. Elsewhere, thunderstorm activity has been
rather limited thus far, but there continues to be a chance for pop
up storms along the lake breezes throughout the evening. Quieter
conditions return overnight under influence of mid-Atlantic high
pressure, ensuring southwest flow through the weekend. Meanwhile, a
strong low pressure system stalls over Manitoba and triggers
numerous thunderstorm complexes west of the Great Lakes. These
complexes are expected to fizzle out by the time they reach Lake
Huron, although brief wind shifts and/or an isolated thunderstorm
cannot be entirely ruled out across northern Lake Huron during peak
heating. Higher confidence in a dry forecast exists with southward
extend afforded by a strong capping inversion. By early next week, a
second low develops over southern Ontario and tracks just north of
Lake Superior, drawing a cold front through the area and clearing
out the warm/humid airmass mid-week. Southwest winds shift to the
northwest as a result of this frontal passage.

&&

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

$$

AVIATION.....BT
DISCUSSION...RBP
MARINE.......MV


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