textproduct: Detroit/Pontiac

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.

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.