877
FXUS63 KDTX 201003
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
603 AM EDT Sun Sep 20 2026

.KEY MESSAGES...

- Periods of rain this morning, with lingering rain chances then
focused mainly south of I-96 this afternoon.

- Seasonably cool conditions will persist into the middle of week.

- Areas of showers are possible again Tuesday night into Wednesday.

&&

.AVIATION...

An elevated nearly stationary frontal boundary remains draped across
southern Michigan this morning, providing a focus for abundant
moisture today. Rain will spread across the Metro Detroit terminals
early in the forecast with coverage gradually shrinking southward
toward the I-94 corridor and stateline this afternoon. The main
aviation concern will be widespread LIFR ceilings this morning. As
high pressure establishes north of Lake Superior, dry northeast wind
will help gradually lift ceilings through the course of the day. VFR
eventually becomes favored by mid afternoon in the north and by this
evening toward Detroit. Wind remains steady out of the northeast
through tonight and gains increasing gustiness Monday morning.

D21/DTW Convection...Thunderstorms are not anticipated through the
forecast.

.DTW THRESHOLD PROBABILITIES...

* High for ceilings at or below 5000 feet through this morning.
  Medium this afternoon, then low tonight.

* Low for ceilings to fall below 200 ft prior to 13z.

&&

.PREV DISCUSSION...
Issued at 300 AM EDT Sun Sep 20 2026

DISCUSSION...

Early morning upper air analysis shows an elevated frontal zone
still anchored locally early this morning, draped within prevalent
lower amplitude mid level westerly flow. Pockets of showers continue
to percolate along the frontal slope and within an environment
featuring higher magnitude low level moisture quality. Shortwave
energy noted on water vapor ejecting out of the mid Mississippi
valley will effectively augment the existing background ascent,
maintaining a high probability for additional intervals of shower
development to occur today. Increasing influence of drying low level
northeast flow as high pressure gains traction to the north likely
establishes a tight north-south gradient for precipitation chances
once the morning round diminishes coverage. Greatest chances from
midday into the evening focused generally along/south of the I-94
corridor. Cooler resident thermal profile entrenched within this
environment ensures high temperatures again arrive mainly in the mid-
upper 60s.

Increasing depth to prevailing east-northeast flow will establish a
period of generally dry and stable conditions early next week as
high pressure stays anchored to the north. Latest NBM guidance still
offers a very low probability for showers to develop near the Ohio
border Monday, acknowledging the lingering presence of deeper
moisture looming just to the south. Some modest cold air advection
tonight will effectively reinforce the seasonably cooler resident
airmass. Highs both Monday and Tuesday projected within the 60-65F
range, with lows dipping into the 40s Tue morning for most locations
outside of the Detroit urban areas. Some degree of diurnally
enhanced gustiness to the wind each afternoon, peaking into the 25
to 30 mph range.

Broader mid level troughing will expand across the northern great
lakes within the Tue night and Wednesday window, as a closed mid
level system pivots southeast into the Ohio valley. There remains a
subset of the model solution space that suggests this interaction
within continued deep layer east flow may effectively draw deeper
moisture back westward into portions of southeast Michigan. Assuming
some form of weak ascent/deformation can emerge, this may present an
opportunity for shower production. Greater potential will eastward
extent, with the outgoing currently peaking chances Wednesday
afternoon. Seasonably cool conditions will otherwise likely prevail
through the end of the week.

MARINE...

Stalled frontal boundary maintains shower chances over the southern
Great Lakes today before expansion of strong high pressure over
northern Ontario finally shunts this front deeper into the Ohio
Valley. Locally, the central Great Lakes reside on the southern edge
of this high resulting in a respectable gradient across the region
throughout the entirety of the early week period. This supports
moderate northeasterly through Tuesday before shifting more easterly
by Wednesday (while maintaining strength). While gales look
unlikely, onshore flow warrants long duration Small Craft Advisories
for all nearshore waters.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Small Craft Advisory from noon today to 10 PM EDT Wednesday for
     LHZ421-422-441>443.

Lake St Clair...Small Craft Advisory from 8 PM this evening to 10 PM EDT Wednesday
     for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory from 8 PM this evening to 10 PM EDT Wednesday
     for LEZ444.

&&

$$

AVIATION.....TF
DISCUSSION...MR
MARINE.......KDK


You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.