textproduct: Detroit/Pontiac

KEY MESSAGES

- A Heat Advisory is in effect today for areas south of M-59. Heat indices peak near 100 degrees today and again Thursday.

- There is a Marginal to Slight Risk for severe thunderstorms this evening and overnight. Damaging wind gusts are the main threat.

- There is a Slight to Enhanced Risk for severe thunderstorms Thursday night. Damaging winds, large hail, and spin-up tornadoes are all possible.

- Not as warm and much less humid Friday through the weekend.

DISCUSSION

Weak mid-level height rises have promoted scattering of morning stratus allowing for respectable solar insolation from late morning into this afternoon. Weak warm front, that had been confined to southern SE MI, washes north in a downstream response to mid-upper trough digging into the upper Midwest/far western Great Lakes through the rest of the afternoon expanding lower 70 dewpoints into the northern CWA. Despite this near-tropical near surface layer, lingering capping inversion is expected to hold through the late afternoon period. As we reach the early evening (~21Z and after), things get murkier wrt to the cap. An EML above 850mb, partially sampled by ILX's 12Z RAOB, is progged to lift into southern lower around roughly 21Z. This feature brings steepening mid-level lapse rates near or in excess of 7.5C/km as well as a ribbon of higher theta-e on its lead nose. While model forecast soundings are still spilt, there is an increasing subset that advertise this in combination with diurnal boundary mixing/growth to weaken our cap sufficiently to allow for at least isolated to widely scattered convective initiation as lift associated with this buoyancy gradient is able to connect thru to the lower level moisture. Should this occur, ample instability is available for convection with an MLCAPE gradient ranging from 1500-2500J/kg and equilibrium levels between 35-40kft. Main limiting factor for strong/severe storms is weaker column wind profiles that will be largely uni-directional shear only 20-25kts at best. That said, given the humid airmass and a well mixed boundary layer, an isolated strong wind gust would be possible. Hail threat, while non-zero, is lesser with freezing levels near 15kft. Additional hazard is torrential rainfall and localized flooding given the aforementioned humid airmass and warm cloud layers exceeding 10kft.

Overnight period brings the next chances for showers and storms as a series of MCS's lift into the Great Lakes. First of these, currently over WI/IL, carries the best shot at any severe potential due to its arrival window latter part of the evening into early tonight. While there is significant uncertainty to what degree this complex holds together all the way into SE MI, dependent on cold pool maintenance, arrival of a SW LLJ strengthens column wind and subsequent shear profiles. As such, severe wind gusts would be possible with any surviving convection through early tonight before the nocturnal boundary layer can attempt to establish itself. A secondary Midwestern MCS looks to then cross or clip the region late tonight- early Thursday morning. Minimal severe chances with this window of showers/storms given the timing falling in the diurnal instability minima. Primary impact instead is clearing out area instability to start Thursday.

Thursday is expected to be similar to today as post-convective subsidence and diurnal mixing promote clearing skies through the morning hours. Airmass remains unchanged with dewpoints hovering in the lower 70s with sunnier skies again allowing temperatures to climb into the low 90s with heat indices rising to the upper 90s to near 100.

Attention then turns to severe potential Thursday evening-night where SPC has the area under a Day 2 Slight/Enhanced risk outlook. Strong PV core rounding the base of the upper Midwest trough Thursday afternoon sparks convection along the attendant surface cold front over the Midwest/Plains. There is high confidence this convection to organize and grow upscale whilst crossing the Mississippi river region while approaching the Great Lakes/Ohio Valley. Where confidence is still low is in how much instability builds back into SE MI over the course of Thursday. There has been a notable shift in a number of CAM outputs (ie ARW, MPAS, HRDPS) for the main instability to hold near the state line promoting a southward drift in the squall favoring better severe wind potentials over the southern portions of the CWA into IN/OH. That said, still have a set (ie HRRR, NSSL, NAM Nest) that favor better northerly advection and hold a more northerly track towards the central and northern CWA-where the current Day 2 Enhanced Risk is. Regardless, wind gusts to 70mph would be the primary hazard with QLCS tornadoes being a secondary threat given the convective mode.

Cold front crosses the area Friday morning ending any lingering showers and ushering in a more seasonably average airmass for Friday and Saturday. A secondary cold front drops out of northern Ontario and through the central Great Lakes early Sunday bringing the next chances for wider spread showers/storms with cooler air following to start the work week.

MARINE

Multiple rounds of showers and thunderstorms are possible this afternoon through Thursday night. A front is currently draped across region which will try to develop some convection this afternoon. A larger complex of severe storms west of Lake Michigan is forecast to track east-northeast across lower MI later this evening bringing the next chance of severe storms to the area. Could be a lull through part of Thursday before a low pressure system tracks from Iowa through the straits Thursday evening into the overnight. This would push a stronger cold front through the region with the next round of storms. Wind gusts in excess of 50 kt and large hail would be the main threats with these storms. This front will pass through early Friday morning, bringing an uptick in westerly winds in its wake as well as a brief period of drier conditions to start the weekend.

HYDROLOGY

A moisture-rich environment remains in place today and Thursday with multiple opportunities for showers and thunderstorms over the next two days. Progressive nature of expected thunderstorms generally limits widespread flooding concerns, although heavy downpours with rainfall rates over an inch per hour will be possible. Localized flash flooding cannot be ruled out, but is mostly confined to low- lying, urban, or flood prone areas.

PREV DISCUSSION

Issued at 142 PM EDT Wed Jun 10 2026

AVIATION...

With upper level ridging in place the challenge of the afternoon forecast revolves around the evolution of capping during the late afternoon hours. 800-700mb moisture advection will have the opportunity to erode convective inhibition and possibly allow for shower/convective initiation. Included Prob30 group for possibility of -TSRA between 23-0z. Will monitor for convection to grow upscale across portions of Illinois this evening and track towards Southeast Michigan between 06-09z. Boundary layer clouds is anticipated again late Thursday morning.

D21/DTW Convection...The potential exists for thunderstorms between 23-01z this evening. There is a potential for showers and thunderstorms again between 06-09z tonight.

DTW THRESHOLD PROBABILITIES...

* Moderate to high for ceiling aob 5000 feet this afternoon. High late tonight.

* Low for thunderstorms late this afternoon and tonight.

DTX WATCHES/WARNINGS/ADVISORIES

MI...Heat Advisory until 8 PM EDT this evening for MIZ069-070-075-076- 082-083.

Lake Huron...Dense Fog Advisory until 5 PM EDT this afternoon for LHZ361>363.

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