348
FXUS63 KDTX 242229
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
629 PM EDT Thu Jul 24 2025

.KEY MESSAGES...

- A Heat Advisory remains in effect through 8pm tonight.

- Thunderstorms will impact portions of southeast Michigan late this
  afternoon through the late evening hours. The strongest storms
  will be capable of producing 60 mph damaging wind gusts,
  torrential rainfall, and flooding.

- Continued warm and humid Friday with lingering chances for showers
  and non-severe thunderstorms towards the southern Michigan border.

- Additional rounds of showers and thunderstorms are likely for
  Saturday and Saturday night. A few storms could be strong to
  severe. Torrential rainfall and localized flooding will remain
  a concern as well.

&&

.AVIATION...

Corridor of convective activity stretches from southern Lake
Michigan to southern Lake Huron. The most active region has been
around FNT, with several small scale cells perking about. This
corridor is expected to settle south with the aid of an approaching
frontal boundary. The storms upstream over Southwest Lower
Michigan are expected to progress east through the evening hours -
likely with a weakening component upon arrival to the immediate
airspace.

The surface flow will transition to west/northwest overnight - then
flip to northeast with the better push of the post-frontal airmass. A
muddled VFR to occasional MVFR cloud field should fill in across
the area behind the frontal boundary. As drier air slow filters in
from the north - ceilings will lift comfortably above 5kft -
especially north of the Detroit terminals. The influence of the
frontal zone may linger across the south - where additional shower
and storm development is possible Friday afternoon.

For DTW/D21 Convection...the northern reaches of the airspace
continue to see weak activity with the focus shift south toward DTW
amount 01z. Persistence of convection will be dwindling through the
late evening as the storms move into a less favorable environment for
organization. Expecting things to quiet down prior to midnight.

THRESHOLD PROBABILITIES...

* Medium for ceilings at or below 5 kft with evening storms, then
  high Friday AM.

* Medium for thunderstorms this evening, with threat ending by 04Z.

* Low for thunderstorms Friday afternoon.

&&

.PREV DISCUSSION...
Issued at 300 PM EDT Thu Jul 24 2025

DISCUSSION...

Dewpoints in the upper 60s and lower 70s, combined with temperatures
in the low to mid 90s have resulted in widespread heat index values
of 100+ degrees. Thus, the Heat Advisory will remain in effect until
8pm this evening. Attention quickly turns to the ling of strong to
severe storms moving east across mid-Michigan late this afternoon,
ahead of a slow moving cold front. As this front continues to move
southeast through the overnight hours, chances for convection
increase. While daytime mixing has lowered our dewpoints and helped
to thin our CAPE profile, this has led to a good environment with
inverted-V soundings and ample DCAPE to remain concerned for strong
to severe thunderstorm wind gusts. The main question remains is what
the storm coverage looks like as we progress through the evening
hours. High-res models have struggled to keep up with radar trends
this afternoon, with most not handling the ongoing convection well.
Based on current radar and satellite trends, do expect this ongoing
line of convection across the Tri-Cities and Thumb regions to
continue to move east and maintain its strong to severe intensity.
Further south, additional development remains possible through the
evening hours. Another complex of storms may also develop around the
southern end of Lake Michigan and move east into our area later this
evening and overnight. Torrential rainfall and localized flooding
remain possible with any thunderstorm activity, especially if we see
any training thunderstorms or high enough rainfall rates as storms
move over urban areas. It is not out of the question that training
thunderstorms could produce a quick 2+ inches of rainfall.

As noted above, the cold front is slow to move through southeast
Michigan tonight and into Friday morning. Mid-level flow becomes
unidirectional along the front so the front will eventually stall
out in the vicinity of MI/IN/OH border. Thus, lingering chances for
showers and storms will persist across far southeast Michigan
through Friday. There will not be a big airmass change behind this
front, so temperatures likely stay in the 80s Friday with muggy
conditions lingering. By Saturday, the stalled out front lifts back
north as warm front in response to a shortwave lifting northeast
across the Great Lakes region. This will bring back the
uncomfortably humid air mass with dewpoints likely climbing into the
lower 70s again. Chances for heavy rain and thunderstorms return as
well, a few thunderstorms could be strong to severe on Saturday.
There are some indications within the medium-range guidance and
probability space for an increased potential for an axis of heavier
rain to develop Saturday evening/night as the main shortwave moves
through. There is low confidence in the positioning of this axis of
heavier rain or training thunderstorms, but the potential is there
for an axis of 2 inches of rain (or higher).

Sunday we should see a break in the active weather, but the warm and
mugging conditions with periodic chances for showers and
thunderstorms return next week.

MARINE...

Most immediate concern for the marine forecast is a broken line of
strong to severe thunderstorms moving across Lake Huron. These
storms will be capable of wind gusts in excess of 34 knots, frequent
cloud to ground lightning, and erratic waves. Storm chances for
areas south of Lake Huron exist later this evening/overnight as a
second line of thunderstorms tracks west to east across the area.
Similar hazards are in play for this line of storms. Expect storm
chances to wane overnight as the second line of storms departs, with
a cold front dropping south through the area early Friday morning
and shifting winds to the north. The front settles near or just
south of the Michigan state line on Friday, which ensures a mainly
dry forecast for most of the area and light northerly winds. A broad
area of weak high pressure fills in but will not do much to cap
storm chances this weekend as the front lifts back to the north and
brings warm/unstable air back into the area. The overall wind field
stays below any longer-fused headlines, but thunderstorm winds may
again exceed 34 knots with storms this weekend. The warm and
unstable pattern persists into early next week before shifting to a
northwest flow pattern mid-week.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Heat Advisory until 8 PM EDT this evening for MIZ047>049-053>055-
     060>063-068>070-075-076-082-083.

Lake Huron...Small Craft Advisory until 10 PM EDT this evening for LHZ421-422.

Lake St Clair...None.
Michigan waters of Lake Erie...None.
&&

$$

AVIATION.....Mann
DISCUSSION...JA
MARINE.......MV


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