textproduct: Detroit/Pontiac

KEY MESSAGES

- Frost Advisory tonight for areas along and north of I-69.

- Seasonably average temperatures return for the midweek period with little to no rain chances.

- Much above normal temperatures possible by next Sunday.

DISCUSSION

Confluent flow amidst a rising mid-level height field prolongs a period of deep subsidence over the region into this evening. Mostly clear skies today have been augmented by shallow lake effect clouds within breezy northwest cold advection. As the anticylone works in tonight and early Tuesday, winds go nearly calm and the cold advection ceases. Max temps only in the lower 60s this afternoon and dew points mixing into the 30s will prime temps to quickly fall into the 40s this evening before settling into the 30s overnight for most areas away from the Metro Detroit heat island and immediate lakeshores. Given the expectation for decoupling of the boundary layer, deep layer dry air, and mostly clear skies, frost formation will be likely for much of northern SE MI early Tuesday morning. Highest confidence in this will be along and north of the I-69 corridor where the surface ridge tracks and NBM hourly probabilities for temps below 37F have jumped to the 70 to 90% range. Thin high cloud still likely to make an appearance before dawn, but shouldn't dampen frost prospects much. A Frost Advisory has been issued in collaboration with neighboring offices.

Notable warm advection commences daytime Tuesday as the ridge axis passes east and milder air is drawn northward by the next wave passing into northern Ontario. System relative isentropic ascent spreads overhead in waves through the day, but the best dynamics and moisture advection are displaced well north of the local area. Ensemble space shows potential for a few sprinkles as far south as the Saginaw Bay region, otherwise just some passing mid and high clouds at times as milder air brings highs into the mid to upper 60s.

The system's cold front is modeled to sink across the area Wednesday afternoon, through an environment that continues to lack deeper moisture and upper support for ascent. A wedge of higher 1000-850mb theta-e precedes the front, allowing temps to peak in the lower 70s before they fall into the 40s behind the front Wednesday night. Slightly cooler, but seasonable temperatures dominate the late week as a broad thermal trough settles over much of the Great Lakes. Some lake effect showers possible in this pattern, but the bulk are forecast to hold across the northern lakes. A stronger ridge is favored to develop over the region this weekend, with a broad Midwest LLJ advecting much warmer temperatures into the vicinity by Sunday. Solution spread remains high in the ensemble space, but fairly high confidence exists for highs in the 70s and a handful of ensemble members suggest potential for temperatures in the lower 80s.

MARINE

High pressure currently building in from the western Great Lakes drifts over the region tonight through early Tuesday promoting rapidly diminishing winds. Influence of said high quickly wanes daytime Tuesday as low pressure slides across northern Ontario resulting in strengthening south-southwest wind locally. Typical uncertainty wrt to thermal stability given active warm advection. Forecast soundings advertise borderline neutral to slightly stable conditions near the water when the strongest gradient arrives early Tuesday night. A few gusts to gales are possible over the north- central waters given the favorable long fetch but local probabilistic guidance continues to downplay a multi-hour period of gales (<20% chance). Running forecast will favor peak gusts in the low 30kt range with no Gale headlines, though Small Advisories are likely for the Saginaw Bay/tip of the Thumb. Surface cold front eventually crosses Wednesday flipping flow to the northwest with persistent James Bay troughing maintaining moderate gusts (20-30kts) through Thursday.

PREV DISCUSSION

Issued at 159 PM EDT Mon Oct 5 2026

AVIATION...

Low impact aviation weather conditions persist today through Tuesday as surface high pressure provides ample stability, stretching from The Plains across the Midwest. Meanwhile, a jet streak aloft will continue to exit toward the eastern Great Lakes which favors minimal cloud cover through tonight. VFR conditions prevail with a period of overnight SKC, until the next plume of moisture streams in overhead during the day Tuesday. Northwest flow with occasional 15+ knot afternoon gusts will drop-off this evening as winds trend toward calm overnight. The surface high centers over Appalachia Tuesday leading to southerly wind shift and light speeds (below 10 knots). Some mid and high VFR cloud should be overhead come the midday hours on Tuesday.

D21/DTW Convection...No thunderstorms forecast through Tuesday.

DTW THRESHOLD PROBABILITIES...

* None

DTX WATCHES/WARNINGS/ADVISORIES

MI...Frost Advisory from midnight tonight to 8 AM EDT Tuesday for MIZ047>049-053>055-060>063.

Lake Huron...Small Craft Advisory until 10 PM EDT this evening for LHZ441.

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