textproduct: Detroit/Pontiac

KEY MESSAGES

- An unsettled pattern continues today into the weekend with scattered showers and thunderstorms at times.

- Temperatures remain seasonable through the weekend.

DISCUSSION

A weak frontal boundary marked by a corridor of dew points in the upper 60s and 70s remains draped NE-SW across Lower MI into northern IN this morning. This will slowly migrate eastward today while what's left of any frontal structure continues to fade. By tonight and into Friday, the front dissipates overhead leaving the area within weak southwest flow downstream of a longwave trough over the Midwest. Additional moisture will work into the area from the Ohio and Mississippi Valleys with weak perturbations aloft bringing bouts of scattered showers and isolated thunderstorms today and Friday. Given the weak/nebulous forcing, any precip is expected to be hit-or- miss and timing generally carries lower than normal confidence through this period.

Guidance favors mainly dry conditions much of the morning before daytime heating produces a weakly unstable and uncapped environment supportive of scattered pop-up showers and isolated thunderstorms through the afternoon. Upper jet entrance region forcing arrives south of M-59 during this window, suggesting the highest coverage of showers sets up there (~40%). HREF/REFS ensemble mean SBCAPE on the order of 500 to 1000 J/kg and mean 0-6 km shear of 25 to 30 kt supports potential for a few stronger updrafts capable of producing heavy downpours and isolated gusty winds up to 40 mph. Coverage should wane this evening with the loss of diurnal instability, but another flare-up of convection will be possible in the south overnight on the nose of a weak LLJ. Otherwise, it will be another mild and muggy night with potential for some patchy fog by early Friday.

A similar weakly forced and uncapped environment exists on Friday, with a slight uptick in instability outlined in ensemble probabilities. The favored window for showers and storms will be the mid afternoon to mid evening diurnal peak, with CAMs suggestive of enough surface convergence to trigger convection. Severe weather chances are low given weak lapse rates, shear, and organization.

A Pacific jet streak tracking into the upper Midwest Friday night will force a cold front across the Great Lakes on Saturday. The more coherent upper forcing tied to the nose of the jet and associated shortwave may outpace the front itself Saturday morning, but enough frontal convergence and instability exists for a chance of showers and storms during the day. Temperature advection is minimal with this front, and seasonable August temperatures are forecast to persist this weekend and into next week. Post-frontal high pressure on Sunday looks to bring some reprieve from the unsettled pattern.

Will need to monitor Sunday night into Monday which presents the next window for more organized convection as several stronger shortwaves pass over a warm/stationary front in the vicinity. The last several runs of ensemble guidance has hinted at potential for heavier rainfall, with latest NBM QMD offering 50% probability for 1+" by 12z Tuesday. LREF is more muted but still shows a wide swath of 25% probability for 1+" in the region. This passes the eye test given the frontal setup, LLJ forcing, and moisture rich environment.

MARINE

A stalled frontal boundary located across southern Michigan will bring the continuation of showers and some thunderstorms through the day. Most activity will be confined south of the northern Lake Huron zone, aligned where the front resides. Winds generally remain light outside of any thunderstorm activity. High pressure builds in the wake of the front late tonight through tomorrow, with a second cold front then moving through Friday to Saturday. This will bring additional chances for showers and thunderstorms leading into the weekend.

PREV DISCUSSION

Issued at 1147 PM EDT Wed Aug 5 2026

AVIATION...

Scattered light showers with isolated thunder chances persist through the first half of the night before the driving wave shifts east. Increasing low level moisture along the front offers a window for at least patchy fog development late tonight over the northern terminals. Ceilings lower into Thursday morning as moisture increases with MVFR likely front PTK-north. Frontal boundary lingers around the southern terminals Thursday allowing for another period of storm chances during the late afternoon-evening coinciding with peak heating.

D21/DTW Convection... There is a chance for a few thunderstorms still work across the northern D21 airspace tonight. Best window for storm chances at DTW arrive Thursday late afternoon-evening.

DTW THRESHOLD PROBABILITIES...

* Moderate for ceilings below 5kft tonight into Thursday.

DTX WATCHES/WARNINGS/ADVISORIES

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