textproduct: Detroit/Pontiac

KEY MESSAGES

- Seasonally cool temperatures persist this week.

- Showers and scattered thunderstorms are forecast Tuesday afternoon and evening.

-Showers and thunderstorms are forecast again Wednesday afternoon into early Thursday morning. Heavy rainfall is possible which may lead to some localized flooding, especially in urban areas.

DISCUSSION

It will be a relatively chilly start to the morning with temps in the 40s and 50s as a result of deep layer cold air advection over the previous 12 to 24 hours. Mid level negative vorticity advection this afternoon will sustain a layer of subsidence from roughly 700 to 400MB. While sfc dewpoints will remain in the 40s, steep low level lapse lapse through diurnal mixing and residual cold air aloft will still support some high based cu. Late day cloud depths may support a sprinkle or some virga, with the dry air in the low levels limiting much if any rain from reaching the ground. Westerly flow will support some subtle warm air advection. This diurnal boundary layer growth should help boost daytime highs into the low 70s.

A short wave pivoting around the upper low in the Hudson Bay vicinity will back the flow to the southwest tonight. Despite very dry air in the boundary layer, the gradient flow will hold mins in the 50s. The southwest flow will advect a little warmer air across Se Mi Tuesday prior to the arrival of the large scale ascent associated with the aforementioned short wave. Sfc dewpoints forecast to rise into the 50s and steep mid level lapse rates will result in a weakly unstable environment with SB CAPE around 1000 to 1500 J/kg. The deep layer shear and instability profiles are not too impresssive for severe weather. However, the inverted V signature on model soundings courtesy of steep daytime low level lapse rates may support isolated strong/damaging wind gusts from any thunderstorm downbursts. With the large scale ascent associated with the short wave forecast to track across Se Mi during peak daytime heating Tuesday, coverage of showers/thunderstorms Tues aftn/evng should be numerous to widespread.

Another wave is forecast to pivot around around the Hudson Bay low and track across the nrn Ohio Valley/srn Great Lakes Wed night into Thursday morning. Exit region upper jet dynamics are shown to support an intense low level jet in excess of 60 knots. Recent model trends have suggested this inflow will drive the instability plume a little farther north (into at least the southern portions of Se Mi). Given the shear profiles, strong/severe convection can not be ruled out. With a warm front likely draped somewhere across Se Mi, model solutions have a good signature for a frontal heavy rainfall event as ample moisture is driven into the frontal boundary, with at least current model solutions indicating a bullseye of theta e advection in the 825-850mb layer across Se Mi. The aforementioned short wave and associated occluded sfc low (forecast to track across Lower Mi) will be fairly progressive, which may limit extreme rainfall. However, 1 to 2 inch rainfall amounts certainly seem plausible.

MARINE

Gradient winds and gusts wane gradually this morning amidst lingering modest lower column flow. Marginal Small Craft Advisory conditions (winds and/or waves) for Saginaw Bay and The Thumb nearshores may recover sooner than forecast. Drier conditions persist today as high pressure migrates across the Tennessee Valley, extending into the southern Great Lakes. This also causes flow to flip southwesterly tonight into Tuesday. The arrival of a low pressure system and it's attendant cold front lead to showers and thunderstorms beginning Tuesday afternoon for the central waterways. A brief break in activity ensues Wednesday due to shortwave ridging, followed by a secondary stronger system Wednesday night into Thursday. More intense convection is possible with the Wednesday night system, capable of damaging winds and large hail. Seasonably strong gradient (non-thunderstorm) winds will also accompany the low. Gusts to gales cannot be ruled out Thursday after shallow mixing profiles deepen (albeit minimally) and 40-50 knot flow materializes within the lowest 3 kft.

HYDROLOGY

Rigorous moisture transport across a warm front associated with a west to east moving low pressure system will result in widespread showers and scattered thunderstorms from Wednesday afternoon into early Thursday morning. Probabilities for rainfall totals of three quarters of an inch to one inch are high across Se Mi. Recent trends are increasing for a wide swath of 1 to 2 inch amounts across portions of the area. The system is forecast to be relatively progressive, which will keep probabilities for rain totals in excess of 3 inches low. Expect this rainfall will result in rises on area rivers and may pose a flood risk to urban areas.

PREV DISCUSSION

Issued at 1153 PM EDT Sun Jun 14 2026

AVIATION...

Cooler and less humid air is gaining ground into SE Mi as late evening surface observations indicate Td in the mid 40s now in the Tri Cities. The inbound air mass and more uniform NW wind bring a clearing trend across the region during the late night.

Monday starts off with mixed high clouds and light westerly wind through the morning leading to high based cumulus for the afternoon. There is also an uptick in westerly wind speed in a steepening pressure gradient between Ohio valley high pressure and low pressure in northern Ontario. Wind gusts increase to around 20 knots until early Monday evening.

D21/DTW Convection... No thunderstorms forecast late tonight and Monday.

DTW THRESHOLD PROBABILITIES...

* None.

DTX WATCHES/WARNINGS/ADVISORIES

MI...None. Lake Huron...Small Craft Advisory until noon EDT today for LHZ421-422-441.

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