textproduct: Detroit/Pontiac

KEY MESSAGES

- A slow moving cold front brings and band of light rain showers with broken coverage across the area Thursday.

- Another round of rain showers with wider coverage and greater intensity develops late Thursday night and Friday morning.

- Dry weather and cooler but still near normal temperatures follow behind the front Friday afternoon and Saturday.

- Warmer temperatures move in Sunday and Monday but also with an active rainfall pattern early next week.

DTW THRESHOLD PROBABILITIES

* Moderate for ceilings at or below 5000 ft Thursday morning.

PREV DISCUSSION

Issued at 347 PM EDT Wed Apr 8 2026

DISCUSSION...

Morning sun helped lift temperatures from frosty morning lows in the 20s before a brief mid level cloud increase from the west which has since dissipated to just patchy coverage. Extra sunshine is helping lift temperatures more into the lower 50s at mid afternoon, although SE wind gusting in the 20 mph range feels cooler and the onshore direction is limiting readings the to 40s near Lake Huron. The now departing mid level clouds represent warm advection in progress across the Great Lakes that continues tonight. Evening temperatures settle into or remain in the 40s and then rise into the lower 50s after midnight as surface wind veers SW and the warm sector of northern Ontario low is drawn into the region.

Dry weather holds for much of tonight as the milder air moves into Lower Mi, and until a band of rain showers reaches the Tri Cities toward sunrise. This occurs within the moisture axis also drawn northward by SW flow ahead of the cold front trailing the Ontario surface low. Model depictions of the lower to mid level theta-e ridge still indicate a narrow and sharp structure within a 50 kt low level jet across the upper Midwest and western Great Lakes this evening. This is where moisture transport, daytime instability, and short wave/frontal forcing all align to produce a more solid and more intense band of showers and scattered thunderstorms. All of this changes as the band reaches central Lower Mi and the Tri Cities toward sunrise. The moisture advection is over, timing is at the nocturnal instability minimum, and the boundary is trending frontolytic on the south flank of the mid level wave. Loss of this larger scale organization supports the diminishing trend in rainfall rate shown in hi-res and regional deterministic models as the front settles through SE Mi during Thursday.

Model projections in today's 12Z cycle maintain solutions that show the front stalling across IN/OH Thursday night as the next 500 mb short wave arrives in the Midwest. This wave reactivates a larger band of rain showers at mid levels of the frontal zone that is timed to move into central and SE Mi mainly after midnight which then lasts through Friday morning. Nocturnal timing in this case is favorable for low level jet intensification downstream and along the 850-700 mb frontal zone leading to a flare-up of elevated convection. The general forecast trend shows a slight northward shift in the rain/snow line and in the position of the consensus QPF axis, both associated with a similar northward shift on the track of the mid level wave and pressure reflection along the surface frontal zone. Rainfall amounts still range widely among deterministic solutions for the 6 hour period ending 12Z Friday and are generally less than 1 inch for the entire 12 hour event ending 18Z Friday, including a tendency to shift new elevated convection toward the surface front Friday morning. Localized 1 inch totals are mentioned in the Hydrology section as high end amounts with low predictability depending on occurrence and location of isolated thunderstorm clusters. Overall event rainfall totals are less than 0.5 inch in AI solutions and ECMWF/GFS ensemble means, which suggests leaning the forecast toward lower values of NBM QPF in the 0.5 to 0.75 inch range before the system exits Friday afternoon.

Eastward passage of the progressive 500 mb wave and larger scale trough axis drives the front much farther south into the Ohio valley by Friday evening. NW confluent flow and a surge of surface high pressure follows to maintain dry weather Friday night and Saturday. The inbound high pressure air mass is projected to be just slightly cooler in temperature guidance that carry highs in the 50s for Saturday, right around normal for early to mid April. Another round of warm advection is well underway across the Great Lakes by early Sunday as the next low pressure system organizes in the Plains states. This system is associated with a southern stream 500 mb trough over the Rockies that generates deep SW flow of Gulf moisture into the Great Lakes meaning warm temperatures but also an active rainfall pattern for early next week.

MARINE...

Southerly flow strengthens tonight across the central Great Lakes as surface low pressure progresses across Ontario, causing gradient winds to increase above 20 knots for much of Lake Huron. A 60 knot low level jet associated with the system also moves in overhead, but low-level stability should limit strong gusts from mixing down to the surface. Gusts should generally be capped below 35 knots, with elevated wave heights being the main marine concern. The wave response will be sufficient to exceed Small Craft Advisory criteria for the southern Huron nearshore zones, therefore an advisory remains in effect. Also, a few gusts to gales cannot be ruled out, especially over the northern Huron waterways, but infrequency should still preclude any gale headlines. The low eventually draws a cold front across the region late tonight into Thursday resulting in several rounds of showers, with low potential for a couple embedded thunderstorms.

A wave lifting out of The Plains leads to additional opportunities for showers and perhaps a thunderstorm Thursday night and Friday, with some light snowfall more likely for the north/central Huron basin. High pressure then builds out of the Upper Midwest to start the weekend with drier and weaker northwest flow. Active weather will be possible again Sunday through Tuesday due to several passing disturbances. Potential exists for gusts to gales late Sunday into Monday.

HYDROLOGY...

A cold front brings a band of rain showers first into the Tri Cities area early in the morning which then moves to the south and east across the rest of SE Michigan during the day. Broken coverage of showers produces rainfall totals generally less than 0.2 inch as the band weakens while moving through the region and then exits by late afternoon. A second round of showers develops mainly after midnight Thursday night and lasts through Friday morning. This system brings higher rainfall amounts over a wider area averaging about 0.5 inch in a 6 to 12 hour time window. There is a chance for localized totals near 1 inch where embedded thunderstorms occur before this pattern also exits southward and eastward Friday afternoon. Flooding potential remains low with this event, although the new rainfall could slightly delay drainage from river and stream systems after the heavy rain that occurred last weekend.

DTX WATCHES/WARNINGS/ADVISORIES

MI...None. Lake Huron...Small Craft Advisory until 4 PM EDT Thursday for LHZ421-422-441>443.

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