textproduct: Detroit/Pontiac

KEY MESSAGES

- Coverage and intensity of showers increase across SE Michigan tonight.

- There is a chance for locally heavy rainfall until showers end with the passage of a cold front Friday morning.

- Low temperatures are projected to reach the mid to upper 30s north of metro Detroit by Saturday morning.

- Cool temperatures continue through the weekend. - There is a low chance for a short period of light rain Sunday.

DISCUSSION

A broad band of showers spans the central Great Lakes and extends into the central Plains this afternoon. It is on schedule to migrate across the rest of SE Mi tonight while gaining intensity along and near the cold front that is already moving into central Lower Mi at forecast issuance. The rainband is sharpened by frontogenesis in the low to mid levels as the mid/upper level trough and jet entrance region move eastward into a more complementary position that is reflected in model depictions of notable 850-700 mb theta-e gradient increase across the frontal zone. The same theta-e projections show the mature moisture axis also still tapping a hybrid tropical Pacific/Gulf supply and feeding it into the Great Lakes along and ahead of the frontal zone. At least a brief period of heavier rain occurs in this setup as the 12Z DTX sounding measured PW near 1.8 inches and as HREF and REFS mean PW touches 2 inches as the system moves through SE Mi tonight. Otherwise, the steady NW to SE pace of the frontal passage limits flooding potential until the pattern exits early Friday morning.

Expansive surface high pressure settling into the northern Plains today builds aggressively into the Great Lakes during the day Friday. It brings an air mass that is cool enough to produce scattered to broken cumulus during the afternoon which becomes dry enough for a rapid clearing trend Friday evening. Radiational cooling then wins out over any lingering light north wind and/or thin cirrus during the night. Guidance low temperatures in the mid to upper 30s look good north of metro Detroit by Saturday morning.

The larger scale westerlies stay progressive during the weekend with a model consensus on the next low pressure system arriving in northern Ontario Sunday. The trailing cold front might be capable of a stray shower as it sweeps through the Great Lakes while high pressure traps Gulf moisture near the coast to mid Atlantic. The front ushers in a new round of high pressure and below normal temperatures as the weather highlight for early next week.

MARINE

Widespread rain associated with a cold front will slowly push southward across Lake Huron tonight before exiting southeast of Lake Erie late Friday morning. Post frontal shallow cold air advection along the lead edge of expansive high pressure over the northern Plains will result in increasing north-northwest winds during the night into Friday. Available guidance suggests moderate to high probability for wind gusts of 25 to 30 knots across the open waters of Lake Huron. This will also help drive hazardous conditions to small craft across the Lake Huron nearshore waters tonight and Friday. The high pressure system will expand across the Great Lakes region Friday night into Saturday, resulting in light winds. The rapid eastward departure of this high by Sunday will drive another frontal system into the region by the end of the weekend. This front will be moisture starved and generally weak, limiting weather conditions to just light rain chances. Its passage will be marked by a veering of the winds from south to west-northwest. Some uptick in the winds is expected over Lake Huron within the post frontal cold air advection. Available guidance indicates the winds remaining below gales.

HYDROLOGY

A large band of showers moves across SE Mi while gaining intensity with the passage of a cold front tonight. The band has access to a tropical Pacific and Gulf moisture supply that fuels brief periods of heavy rain within the more persistent band. There is high confidence in rainfall totals up to 1 inch and medium confidence in totals of 1 to 2 inches during a 3 to 9 hour period. The low-end chance for totals to reach or exceed 2 inches requires a frontal passage that would be slower than projected at this point in the forecast. This scenario limits potential flooding to minor instances in low-lying areas with ponding water on roads across the region until the rain quickly ends post-front Friday morning.

PREV DISCUSSION

Issued at 129 PM EDT Thu Oct 1 2026

AVIATION...

Stream of Gulf moisture ahead of a cold front and passage of this front will maintain widespread rain across KMBS through the evening and will increase coverage across all other TAF sites tonight. MVFR to IFR cigs are expected with the onset of rain showers along with likewise restrictions to visibility under the more moderate rainfall intensity. There will be a low chance immediately along the front for acute stronger rain showers within a 1-3 hour window that can bring very brief periods of LIFR cigs. Otherwise, winds will quickly back from southwest to northwest after the passage of the front with rapid dry air advection bringing quick improvements to ceiling heights in the wake of the front.

D21/DTW Convection...Low potential for thunderstorms through this forecast period.

DTW THRESHOLD PROBABILITIES...

* High for ceilings below 5000 feet this evening.

* Low for thunderstorms this evening and overnight.

DTX WATCHES/WARNINGS/ADVISORIES

MI...None.

Lake Huron...Small Craft Advisory from 10 PM this evening to 10 PM EDT Friday for LHZ421-443.

Small Craft Advisory from 10 PM this evening to 4 AM EDT Saturday for LHZ441-442.

Lake St Clair...None.

Michigan waters of Lake Erie...None.