993
FXUS63 KDTX 182242
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
642 PM EDT Sat Jul 18 2026

.KEY MESSAGES...

- A Severe Thunderstorm Watch remains in effect for parts of
Southeast MI this afternoon and early evening.

- An Air Quality Alert is in effect north of I-69 today due to
wildfire smoke returning from the north this afternoon. A statewide
Air Quality Alert has been issued for Sunday.

- Benign weather Sunday and Monday before the next round of showers
and thunderstorms arrives Monday night into Tuesday.

&&

.AVIATION...

The cold front has now exited south of metro Detroit. Ongoing dry
stable air advection will inhibit additional convective activity.
Post frontal gusty winds within ongoing cold air advection will
gradually degrease during the evening as daytime mixing ceases. The
post frontal north-northwest flow has however driven the smoke plume
back into Se Mi. This will result in MVFR visibilities tonight into
early Sun morning. Most recent HRRR near-surface smoke model suggest
the north-northeast flow on Sunday will drive the smoke out of much
of Se Mi during the course of the day.

D21/DTW Convection...No thunderstorms are forecast through the next
30 hours.

.DTW THRESHOLD PROBABILITIES...

* Low in ceilings aob 5000 feet Sunday.

&&

.PREV DISCUSSION...
Issued at 338 PM EDT Sat Jul 18 2026

DISCUSSION...

Today`s cold front has reached northern Metro Detroit and will
continue to advance southward before exiting the area by early
evening. The bulk of deep convection along the front so far this
afternoon has been east of I-75 where deeper moisture and better
frontal convergence appear to have set up. A Severe Thunderstorm
Watch remains in effect for areas south of the front as we continue
to monitor additional development. Wind gusts of 45 to 65 mph will
be the primary threat. Based on current trends, suspect we will be
able to end the watch locally before the current 8pm expiration
time. Behind the front, breezy northwest wind has pulled down some
of the northern Great Lakes wildfire smoke plume. This will take
residence through the evening into tonight. Current visibility and
AQI observations indicate a lower concentration of PM2.5 than was
seen earlier this week.

Weak mid-level height rises allow high pressure to build into the
Great Lakes on Sunday, with northeast flow through much of the day
bringing in a dry air mass with seasonable temps. One or more
additional bands of wildfire smoke will likely work across the area
but available models generally show a decreasing trend in
concentration with time. The high passes into the Mid-Atlantic on
Monday with southwest return flow bringing rising thicknesses and
slightly higher temps. Another dry day is forecast as deeper
moisture will hold farther upstream until Monday evening. A
shortwave ushers in a plume of deeper moisture along the surface
warm front Monday night and brings the next round of showers and
thunderstorms. Severe prospects are uncertain given the mainly
nocturnal timing, but some pockets of heavy rain will be possible.
The cold front will lag behind, likely passing through during the
day Tuesday. This leaves the door open for some additional
convection Tuesday but chances may be hampered by the activity
Monday night and Tuesday morning.

The upper air pattern shows an amplified trough tracking across
northern Ontario and the Great Lakes Tuesday into Wednesday. 850mb
temps are modeled to fall to the single digits C by Wednesday, which
favors cooler highs in the 70s. Deep cyclonic flow and passing
shortwaves aloft bring potential for showers. Northwest flow remains
pervasive over the region into the late week as a strong ridge
dominates the western CONUS - this keeps seasonable temperatures and
lower humidity around locally.

MARINE...

Cold front settles south of the region this evening. A brief period
of gusty post-frontal northwest winds will exist through early
tonight, with an accompanying increase in wave action along the
nearshore waters. This will maintain a period of small craft
conditions lasting into tonight. Benign weather conditions with
lighter winds will then exist Sunday as high pressure builds across
the area. Unsettled conditions may develop again by late Monday and
Monday night, as a strong low pressure system tracks across Ontario.
Gusty winds ahead of the attendant front may lead to small craft
advisory conditions Monday, particularly across Saginaw Bay.
Potential for showers and thunderstorms will increase during this
time.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Beach Hazards Statement until 10 PM EDT this evening for MIZ049.

Lake Huron...Small Craft Advisory until midnight EDT tonight for LHZ421-422.

     Small Craft Advisory until 4 AM EDT Sunday for LHZ441>443.

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

$$

AVIATION.....SC
DISCUSSION...TF
MARINE.......MR


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