textproduct: Detroit/Pontiac

KEY MESSAGES

- Showers and thunderstorms are likely this evening and overnight. Scattered storms may be severe with wind gusts to 60 to 70 mph and localized heavy rainfall the main threats.

- Additional showers and thunderstorms are likely Friday night and Saturday. Some storms may be strong and produce heavy rainfall.

- Mild conditions Friday and Saturday, then trending cooler again Sunday into early next week.

DTW THRESHOLD PROBABILITIES

* Moderate for ceiling at or below 5000 ft this evening, then high late tonight and Friday morning.

* Moderate to high for thunderstorms this evening, and low late tonight.

PREV DISCUSSION

Issued at 410 PM EDT Thu Apr 2 2026

DISCUSSION...

Low pressure over IA tracks northeast into the Straits tonight and its surface warm front is currently positioned from near New Buffalo along the state line to between Toledo and Findlay. Persistent easterly component of low-level flow holds the stable marine layer over much SE MI into the evening and delays the arrival of surface based instability, holding a dry forecast for the next few hours. Meanwhile strengthening southwest gradient wind will cause the warm front to make farther northward progress across western and central Lower MI, resulting in an instability gradient oriented NW to SE across central Lower MI through this evening. The upper shortwave driving the surface low has a negative tilt with strong upper jet divergence aiding in convective development along a pre-frontal trough over southern IL. This convection is forecast to track northeast across Lower MI through this evening, with initial multicell storms favored to congeal into a linear mode with current trends tracking it through SE MI between 8pm and midnight.

Buoyancy will be the limiting factor for severe weather tonight as the resident stability will be slow to dislodge, and there is expected to be a general weakening trend as convection arrives. However, there remains a threat for damaging wind gusts of 60 to 70 mph given the powerful kinematic background. The inbound LLJ in the warm sector will be characterized by 65 kt flow at 850mb and 50 to 60 kt down to 925mb or roughly 2 kft AGL. If storms arriving from the west can stay rooted in the surface layer, descending parcels will be capable of dragging the higher momentum to the surface. Highest confidence for this to occur is west of US-23 with decreasing probability with eastward extent given increasing stability. A higher moisture environment with PWAT rising to near 1.40" brings potential for localized heavy downpours as well. Storm motion at nearly 60 kt will keep this activity transient and mitigate flooding concerns for most areas, but some locales around the Saginaw Valley may see repeated storms and with antecedent wet conditions this additional rainfall may cause localized minor flooding tonight. Low probability for an embedded brief tornado also exists near the warm front/CAPE gradient where SRH will be maximized as convection moves in. This is particularly true if any segments deviate to the right of the prevailing NNE storm motion.

As the warm sector passes through overnight, neutral thermal profiles allow for gusts of 30 to 40 mph at times before the LLJ moves out. The cold front passes through Friday morning with little ascent left as the parent system quickly tracks into western Quebec. Some lighter showers and perhaps a rumble of thunder will be possible, then clearing skies and weakening wind results in a pleasant Friday afternoon with temps in the 70s south and 50s north.

The next system takes a very similar track from the Midwest/Mid Mississippi Valley into the northern Great Lakes on Saturday. The warm front will be positioned south of the stateline late Friday before being forced northward Friday night. Brief residence of the warm sector follows early Saturday before the cold front sweeps through later in the day. Instability will again be a limiting factor for stronger convection, and the current SWODY3 outlines SE MI in the general thunder category. Localized heavy rainfall will be a possibility and WPC shows all of SE MI in a marginal risk for excessive rainfall.

A cooler pattern commences Sunday into the early part of next week as longwave troughing sets up over the Great Lakes. A clipper tracks through on Monday bringing a chance of rain and snow showers, but otherwise drier conditions will prevail during this period. Another frontal system in the Great Lakes vicinity brings increasing potential for another active period during the late week.

MARINE...

A modest gradient exists over the central Great Lakes today, positioned between approaching low pressure from The Plains and stalled high pressure over Quebec. A warm front associated with the low has been slow to lift into the southern waterways, keeping mixing depths very shallow this afternoon. Still, a period of on- shore flow brings elevated waves to Saginaw Bay and the southern Lake Huron shoreline, where Small Craft Advisories remain in effect. Gusts across portions of northern Lake Huron will appoach gales this evening, but the lack of persistence precludes a last minute Gale Warning. The warm front precedes the track of the low tonight, toward The Straits, with winds veering SSW with time, from south to north. The system's low-level jet, featuring 60 knot flow below 3 kft, will struggle to mix down given low level stability, therefore no additional gale headlines were issued. Some strong to marginally severe thunderstorms will affect some waterways tonight, with the main threat being strong gusty winds in excess of 34 knots.

Drier conditions with decreasing winds expected Friday, after the system's cold front clears through. However, unsettled weather returns Friday night and Saturday with a similarly tracking warm front and surface low. This should bring renewed modest easterly winds, areas of gusts approaching gales, and additional thunderstorms, some of which could be strong or marginally severe.

HYDROLOGY...

Early day showers and thunderstorms brought rainfall amounts ranging between 0.10 and 0.60" with the higher amounts focused across the Saginaw Valley and I-69 corridor. Additional showers and storms will track across the area this evening into tonight. An increasingly moisture-laden environment will support heavy downpours at times, but fast storm motion of over 50 mph will limit residence time for most areas. The exception will be the Saginaw Valley where some potential for some training storms exists. Additional rainfall amounts through tonight for this area are forecast to range between 0.30 and 0.80" and localized flash flooding will be possible. Areas farther south are forecast to receive up to 0.30" which will limit flooding concerns.

Another period of showers and storms is expected Friday night into Saturday with additional rainfall amounts forecast to range between 0.50 and 1.00". Today's and Saturday's rainfall will cause rises on area rivers and bring potential to reach flood stage, with highest confidence across the Saginaw Valley. River crests are forecast to occur this weekend.

DTX WATCHES/WARNINGS/ADVISORIES

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

Small Craft Advisory until 10 AM EDT Friday for LHZ442-443.

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