textproduct: Detroit/Pontiac

KEY MESSAGES

- Showers and embedded strong thunderstorms work through southeast Michigan tonight and Sunday morning.

- Dry Monday, but showers and possible storms return Tuesday afternoon and late Wednesday/Wednesday night.

- Heaviest rainfall looks to be Wednesday night, with the potential to exceed 1 inch.

UPDATE

Expansion of showers and thunderstorms is on track to occur across central and southern Lower Mi, developing both overhead and from the west toward midnight. The best chance for strong to severe storms is from midnight until about 3 AM, followed by increasing coverage of showers but decreasing intensity of storms through Sunday morning.

Mid evening surface analysis indicates the cold front settling just south of the Straits as low 60s Td pools in the leading moisture axis through central lower Mi. This low level setup is shown in hourly mesoanalysis and short term forecasts to support MLCAPE near 1000 J/kg north of I-69 until fading after 4 AM through sunrise. The approach of the mid level wave erases the subtle cap that has been in place along the bulk of the front west of Lake Huron, and also further improves an already stout wind field. The profile starts out with moderate low level curvature and transitions quickly toward more straight-line as the cold front fills in. Convective mode has a chance for at least elevated mesocyclone structure to support hail and then damaging wind in any linear transitions with time. Storm intensity decreases while enough elevated instability remains to support increasing coverage of showers as the front moves through the region and the short wave overhead through Sunday morning.

PREV DISCUSSION

Issued at 703 PM EDT Sat Jun 13 2026

AVIATION...

VFR consists of thickening cirrus over the DTW corridor and mid level clouds toward FNT and MBS to start the forecast. The mid level cloud pattern is ahead of a cold front extending from the Straits into central IA, and is expected to be the focus for showers and thunderstorms as it moves through Lower Mi during the night. The best chance for storms is projected toward FNT and MBS where instability holds on longer after sunset. Showers grow in coverage while storm intensity gradually weakens as the pattern settles across the rest of SE Mi during the late night and through Sunday morning.

The added boundary layer moisture provided by the showers/storms promotes expansion of MVFR ceiling along and behind the front. This becomes the prevailing condition toward sunrise from the initial wind shift at DTW to the more northerly wind shift near MBS. There is some improvement into VFR as the front moves farther into the Ohio valley and the SE Mi wind field becomes a more general NW flow of cooler and less humid air during Sunday afternoon.

D21/DTW Convection... There is a low chance of thunderstorms within an expanding area of showers late tonight and Sunday morning.

DTW THRESHOLD PROBABILITIES...

* Low for a thunderstorm after 08z Sunday.

PREV DISCUSSION... Issued at 312 PM EDT Sat Jun 13 2026

DISCUSSION...

A seasonably strong polar upper-level low (541 DAM at 500 MB) residing over northern Ontario looks to remain nearly stationary for the next 7 days. This will allow the tracks of the upper-level wave train with the prevailing jet stream to reside over or even south of the Great Lakes region for the bulk of the extended period. This setup will bring periodic chances of rain showers and possible thunderstorms, along with near-normal (slightly below) temperatures.

The first round of activity will move through this evening into Sunday morning (from north to south), as a cold front slowly sinks south. A narrow but healthy moisture plume (PW values up to 1.5 inches) and an 850-700 MB Theta-e ridge are tracking through the northern third of the CWA this evening. However, instability looks to be modest, with MUcapes around 1000 J/kg (better instability over northern lower Michigan with colder 500 MB temps). None-the-less, with stronger mid-level winds (50-60 knots in the 700-500 MB layer) and downdraft capes up around 1000 J/kg, isolated damaging winds can not be ruled out- hence the marginal risk of severe storms north of I-69. Mid-level rates are decent as well, and with wet bulb zero heights around 10kft, hail is possible as well. However, given the weak cape and updraft strength, it may be difficult to get much more than small hail.

The 500 MB shortwave trough axis clears southeast Michigan Sunday afternoon, ensuring a dry end to the day as good post wave subsidence kicks in. However, there has been a slower trend with the passage; if this continues, enough diurnal instability may build once again to warrant concern for isolated strong to severe thunderstorms, particularly over eastern sections of CWA.

A damping upper-level wave will move out of the Midwest Sunday night, tracking along and south of the southern Michigan border. The environment will be too dry and stable to support any shower activity over southern Lower Michigan on Monday. A much stronger upper-level wave pushing into the Western Great Lakes on Tuesday should be sufficient to develop numerous showers and possible thunderstorms Tuesday afternoon into evening. Yet another upper level wave expected to follow quickly, arriving late Wednesday and supporting more rain showers by Wednesday evening. Euro ensembles indicate a greater than 90 percent chance of a tenth of an inch or more of QPF Wednesday night, which is in line with the outgoing high NBM pops.

MARINE...

Several strong to severe thunderstorms are working across central Lake Huron this afternoon leading to gusty winds and large hail, addressed via SMWs. Elsewhere, warming coastal water temperatures beneath modest low-level winds facilitate favorable mixing this afternoon, leading to gusts in excess of 25 knots. The Small Craft Advisory for Saginaw Bay and The Thumb will remain in effect through this evening due to gusty winds and elevated wave heights, before the marine boundary-layer decouples. Southwesterly gradient winds then weaken and veer toward the northwest overnight as a cold front crosses through the central Great Lakes. This boundary will also lead to additional showers and thunderstorms, some of which may be strong to marginally severe late tonight and into Sunday. Winds will stay elevated around 20 knots, but out of the northwest on Sunday. Additional Small Craft Advisories may be needed for Saginaw Bay and The Thumb during the afternoon/evening hours. Breezy conditions return each afternoon early next week, but dry weather should prevail midday Sunday through at least Tuesday morning.

DTX WATCHES/WARNINGS/ADVISORIES

MI...None.

Lake Huron...Small Craft Advisory until 10 PM EDT this evening for LHZ421-422- 441.

Lake St Clair...None.

Michigan waters of Lake Erie...None.