textproduct: Detroit/Pontiac

KEY MESSAGES

- Warmer and much more humid today with periods of showers.

- Coverage and intensity of rainfall increases later today with a chance for locally heavy rain this evening and early tonight.

- Cooler temperatures and drier weather arrives midday Friday, continuing through the weekend and into next week.

DTW THRESHOLD PROBABILITIES

* Low for ceilings below 5000 feet this morning becoming high after 00z this evening.

* Low for thunderstorms this evening and tonight.

PREV DISCUSSION

Issued at 434 AM EDT Thu Oct 1 2026

DISCUSSION...

Significant tropospheric moistening was sampled via the 01.00Z KDTX RAOB, marked by vertical continuity in saturation and a measured PWAT of 1.70 inches. This modified tropically sourced air mass has allowed overnight showers to percolate with ease beneath sustained perturbed flow aloft. The latest forcing mechanism has been attributed to a series of shortwave impulses positioned ahead of an inbound longwave trough moving eastward over southern Canada, and downstream of a southern CONUS closed low. The southern wave has been responsible for the influx of eastern Pacific and Gulf moisture, upholding the appropriate environment for this extended period of rainfall.

The low-level jet moisture connection is fully engaged early this morning, with both increasing magnitude (30+ knots) and trajectory continuity. Latest progs indicate the confluent stream arcs back to Texas where the remnants of Hurricane Polo merge with Gulf-wide theta-e advection. Additionally, the two synoptic waves will begin to phase during the PM hours, leading to a rise in upper-level divergence and local theta-e convergence. This lends continued concern for the localized risk of heavy rainfall later today, especially as a cold front extending from the northern system tracks southeastward across Lower Michigan. The period of greatest concern will be as the frontal slope engages the peak in low-level moisture transport late this afternoon into the evening timeframe, while the system's deformation axis centers overhead. See the Hydrology section for additional details.

Latest NWP suite indicates peak 3-hourly rainfall rates between 00Z and 06Z tonight as the front pushes through. Winds flip northwesterly immediately behind the surface front tonight, although showers will be slower to clear. Once aggressive post-frontal system- relative isentropic downglide builds in, rainfall will quickly conclude. Dry weather is then forecast by mid-morning Friday as the Great Lakes reside downstream of building 1028 mb high pressure moving into the Upper Midwest. Seasonably cool and dry as the ridge dominates. A clipper system could bring a few sprinkles through Sunday morning, while thermal troughing persists. 850 mb temperatures crater early next week, with sub-0C values possible. Morning frost concerns may arise should lows drop into the upper 30s.

MARINE...

Southwesterly winds will continue out ahead of an approaching cold front, which arrives and stalls over southern Lower Michigan today. With warm advection leading to more stable profiles and showers moving through during this timeframe, wind gusts are expected to top out only around 25 knots. With the front hung up until night, the post frontal cold advection now looks slower; thus, the potential for northwest wind gusts reaching or exceeding 25 knots looks to be late in the day on Friday as 850 MB temps lower into the mid single digits by Friday.

A large area of high pressure then builds in behind the departing cold front on Friday into Saturday. This will bring lighter winds for the first half of the weekend. A stronger low tracking through the northern Great Lakes for the second half of the weekend brings another opportunity for winds to reach or exceed 25 knots over Lake Huron.

HYDROLOGY...

A mid to late week rainfall episode continues today, peaking this evening and early tonight. It occurs as tropical moisture streams into Lower Michigan, along and ahead of an approaching Midwest cold front. A more persistent band of rain is established across the area this afternoon as the cold front moves through the region by tonight, when moisture parameters peak. High confidence in rainfall totals up to 1 inch and medium confidence in totals over an inch. The low-end chance for system rainfall totals to reach 2 inches requires a slower frontal passage, leading to a longer window for persistent rainfall. The chance exists for minor flooding of low- lying areas and ponding on roads across the region until the rain quickly ends post-front Friday morning.

DTX WATCHES/WARNINGS/ADVISORIES

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