445
FXUS63 KDTX 020805
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
405 AM EDT Wed Jul 2 2025

.KEY MESSAGES...

- Afternoon/evening thunderstorms will be possible each day today
  through Friday (Independence Day).

- A Marginal Risk for severe weather is in place today north of I-94
  and Thursday south of M-59. Isolated wind gusts to 60 mph will be
  the main concern.

- Seasonable temperatures expected today and Thursday with a warm up
  this holiday weekend. Temperatures Saturday and Sunday may exceed
  90 degrees.

&&

.DISCUSSION...

Clear skies observed on satellite across the Great Lakes this
morning ensure a sunny start to the day for SE Michigan with
overnight lows in the low 60s right around normal for early July
standards. With the exception of the nocturnal stable layer, expect
this morning`s RAOB to look very similar to the 00z observation with
an inversion centered around 7.0 kft agl and deep layer stability
above that. Throughout the day, vertically stacked low pressure near
Hudson Bay will ease south to cool mid-levels especially over the
Tri Cities and Thumb regions. This ultimately leads to the
development of a narrow ribbon of instability and mid-level lapse
rates of 6-6.5 C/km that will be engaged by multiple weak shortwaves
this afternoon and evening. Scattered showers and thunderstorms will
develop in response to these features, with the greatest coverage
north of I-69. Given weak mid-level flow (less than 30 knots),
updrafts will struggle to organize on a widespread basis although
well-mixed/dry boundary layer conditions could lead to a few
instances of gusty winds as storms collapse. SPC has designated a
Marginal Risk of severe weather in the SWODY1.

The Hudson Bay low dives southeast overnight and drives a higher
amplitude trough and upper level jet into Lake Huron by Thursday
morning. At the surface, high pressure fills in from Canada to
establish a low level deformation axis overhead that will focus
shower/thunderstorm potential more toward southwest lower MI
Thursday afternoon-evening. Should see a sharp delineation to the
diurnal cumulus field which will be a proxy for surface-based
instability and thus thunderstorm potential. Temperatures will be a
few degrees cooler to the north/east of this boundary, but
ultimately all areas will see daytime highs in the 80s on Thursday.
With the stronger synoptic wind field in place (35-60 knots spanning
SE Michigan), any thunderstorms that do form could become organized
but coverage does not look all that high in the latest hi-res
output. SPC has also designated a Marginal Risk of severe weather in
the SWODY2.

Friday marks the beginning of a pattern transition to a warmer and
more humid airmass as the ridge over the Intermountain West begins
to fold into SE Michigan. Throughout the day Friday, this ridge
builds to ~594 dam while veering wind profiles locally suggest the
beginning of warm advection into the area. Building heights aloft
help strengthen the surface anticyclonic circulation, which will
have potential to completely clear out instability from SE Michigan
for Friday. NBM PoPs highlight the more bearish solutions (00z Euro)
that clear out the instability completely to support a dry
Independence Day. However, there still are bullish solutions (00z
GFS/NAM) that draw the warm front back into the area by Friday
afternoon. The drier Euro solution would result in warmer daytime
highs for the holiday as well, in the mid to upper 80s, which would
be tempered if convective cloud can develop.

The ridge will push fully overhead this weekend which results in
another round of hot and humid conditions for SE Michigan. A dry
forecast for Saturday can be attributed to the strong subsidence
signal near the ridge axis. Temperatures both Saturday and Sunday
will have potential to exceed 90 degrees while heat indices reach
the mid-90s.

&&

.MARINE...

A ridge of high pressure extends from the Midwest into the Great
Lakes, promoting stable conditions and southwest wind around 10 to
15 kt early today. Chances for scattered showers and thunderstorms
increase through the afternoon as a weak cold front approaches from
the north by this evening. Most showers and storms will be focused
across Lake Huron, and isolated storms will be capable of producing
winds in excess of 40 kt and hail. Post-frontal wind organizes out
of the northwest on Thursday, remaining light. High pressure builds
directly across the region Thursday night to maintain light wind and
waves into Friday. A warm front then lifts across the region on
Saturday, setting up a breezy southwest flow that brings in warmer,
more humid, and unsettled conditions for the weekend.

&&

.PREV DISCUSSION...
Issued at 1202 AM EDT Wed Jul 2 2025

AVIATION...

VFR clear sky is solidly in place over Lower Mi late tonight through
the morning mainly due to weak high pressure reaching north from the
mid MS/MO valleys. There is no meaningful cloud potential until the
afternoon when daytime instability builds a cumulus field that leads
to scattered thunderstorms from about mid afternoon into Wednesday
evening. Pop-up showers and isolated storms are possible across the
area during peak heating while a more organized pattern develops
from northern Lower Mi into the MBS to FNT area late in the day and
Wednesday evening.

For DTW/D21 Convection... No thunderstorms late tonight through the
morning. An isolated afternoon thunderstorm is possible around DTW
while greater coverage resides mainly north of FNT.

 THRESHOLD PROBABILITIES...

* Moderate for ceiling 5000 ft or less Wednesday afternoon.

* Low for thunderstorms Wednesday afternoon and evening.


&&

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

$$

DISCUSSION...MV
MARINE.......TF
AVIATION.....BT


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at www.weather.gov/detroit.