842
FXUS63 KDTX 040357
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1157 PM EDT Thu Jul 3 2025

.KEY MESSAGES...

- Mainly dry conditions through Saturday, outside of a chance (20-
  30%) for an isolated shower or thunderstorm Friday afternoon and
  evening.

- Warm up for the holiday and this weekend with highs in the upper
  80s on Independence Day and low 90s Saturday and Sunday.

- Chance (40-50%) for showers and thunderstorms late in the day on
  Sunday.

&&

.AVIATION...

Slightly cooler and less humid air has settled over most of SE Mi to
the north and east of the front stalled from the Ohio border into SW
Lower Mi. VFR clear sky is mixed with patches of cirrus and mid
clouds percolating within elevated portions of the front late
tonight. The front also maintains a sharp surface Td gradient and
has adequate structure aloft to at minimum help maintain cloud
debris from upper Midwest thunderstorm clusters and may be able to
sustain a stray shower during the morning. A few patches of stratocu
are also possible off the Lakes as low level wind veers toward the
south. Upper Midwest low pressure then pulls the front back
northward in the afternoon in further support of scattered showers
and storms into Friday evening. Mostly uniform weather timing from
south to north along the terminal corridor.

For DTW/D21 Convection... There is a low chance of thunderstorms as
warmer and more humid air returns to the DTW vicinity in the
afternoon.

THRESHOLD PROBABILITIES...

* Moderate for ceiling 5000 ft or less in the afternoon through
  Friday evening.

* Low for thunderstorms in the afternoon through Friday evening.

&&

.PREV DISCUSSION...
Issued at 255 PM EDT Thu Jul 3 2025

DISCUSSION...

Mid-level heights to increase through the day and into the end of
the week as an upper-level ridge axis pivots over the Great Lakes by
12Z Saturday. This will result in increasing temperature trends that
max out in the 90s by the weekend along with some increased
humidity. The boost in stability will also favor generally dry
conditions, however, subtle forcing will bring the chance (20-30%)
for isolated shower and thunderstorm chances both for this
afternoon/evening and again tomorrow.

Weak low-level convergence along a sluggish advancing cold front
which will gain momentum later tonight, influenced by northeast flow
off of Lake Huron, will be the source of initiation for any rain
shower or thunderstorm development. The kinematics are decent with 1-
6km shear values of 35 knots, however, buoyancy will be competing
with weak capping between 600-500mb that the weaker low-level
forcing will likely not be able to compensate for. The better
moisture/CAPE will be confined in a line around and south of Owosso
to Detroit where PoP values of 20-30% reside. Rain chances end late
tonight with the loss of daytime heating and clearance of the front
into southwest Michigan.

A surface high pressure system becomes slightly more defined over
the eastern Great Lakes tomorrow under better upper-level confluent
flow, where anticylonic flow then pivots the frontal boundary back
over SE MI, providing secondary chances for some shower or storm
development tomorrow afternoon and evening. An outflow boundary from
overnight convection west of Lake Michigan and/or lake breezes off
the Saginaw Bay or west Lake Erie will also be some additional
sources for CI tomorrow, with the western-third of the cwa holding
PoP chances between 20-25%, aligned with where the CAPE boundary ends.
There are some minor uncertainties regarding the strength of the
aforementioned capping, however, degraded shear values and CAPE
density relative to today precludes any stronger wording of coverage
under the backdrop of the increased ridging.

Saturday maintains the highest confidence of dry weather under the
ridge axis where 850mb temperatures of 20C set up over the state.
Temperatures increase into the lower 90s as a result (possibly
pushing mid 90s across the urban landscapes) while dew points rise
into the upper 60s. A series of shortwaves will start to break down
the ridge into Sunday with a prefrontal trough and cold front then
bringing the chance for showers and thunderstorms later in the day
Sunday. At present time this front looks to move through SE MI later
in the day which will allow for temperatures to return back into the
upper 80s to low 90s, with some relief from the heat entering Monday
after the passage of the front.

MARINE...

An isolated shower or storm remains possible over Lake St Clair/Erie
this afternoon. Otherwise the slow moving, weak cold front finally
clears the southern Great Lakes this evening as high pressure builds
in across the central Great Lakes. A warm front lifts through the
region Friday ushering in a return of hot, humid conditions for the
weekend though no storms are anticipated with this frontal passage
or Saturday. SW winds increase following the fropa with strongest
winds focused over the central portions of Lake Huron where gusts
will be able to reach around 20kts. Low pressure sliding over the
northern Great Lakes drags a cold front into the area late Saturday
night-Sunday offering the next chances to see numerous showers and
thunderstorms. These chances look to linger into daytime Monday for
the southern Great Lakes as the front is slow to fully vacate. High
pressure then briefly follows late Monday through Tuesday.

&&

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

$$

AVIATION.....BT
DISCUSSION...AM
MARINE.......KDK


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