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.

UPDATE

The 12Z DTX sounding showed a mid level capping inversion based near 560mb which is not well resolved by the 06Z model suite. Ample moisture below this inversion will ensure periodic cloud cover through the day. Through the first part of the day Se Mi will lie between a short wave lifting into the straits and the remnant MCS complex across the Mid Mississippi/Lower Ohio Valleys, with broad meso scale subsidence across the forecast area. The cloud cover is expected to result in a variation in instability across the area this afternoon, with hi res guidance suggesting SB CAPE ranging anywhere from 600 to 1200 J/kg as boundary layer moisture remains elevated. There are at least a couple mechanisms which may break any residual mid level capping today. A mid level short wave shedding off the MCS and now lifting into cntl IL/IN may clip the southern portions of Se Mi late this afternoon/evening. A respectable region of enhanced boundary layer convergence across the thumb and eastern sections of the area due to the Lake Huron marine layer may also contribute to a convective release later in the day. These factors remain supportive of low chance pops late this afternoon and evening.

PREV DISCUSSION

Issued at 657 AM EDT Thu Aug 6 2026

AVIATION...

Mid and high clouds clearing eastward with the area of showers have opened the nearly saturated boundary layer to further cooling prior to sunrise. Fog and low stratus have quickly filled in over southern Lower Mi as a result. IFR ceiling and visibility from MBS down to FNT is expected to expand toward PTK and the DTW corridor during the morning. These conditions occur in and around the frontal zone stalled across the region which sets up an environment of slow improvement through MVFR by late morning and then low end VFR early to mid afternoon.

Prospects for renewed development of showers and thunderstorms becomes the focus this afternoon. Increasing afternoon instability combines with the diffuse frontal zone to promote greater coverage along and south of the I-69 corridor with an added component from activity that survives moving northward from IL/IN. Activity continues through mid evening and then transitions to showers over the DTW corridor into the late night hours. Boundary layer moisture content remains elevated for a mix of low end VFR and MVFR clouds through sunrise Friday.

D21/DTW Convection... A mid afternoon to mid evening time window remains open for scattered thunderstorms in and around the DTW airspace.

DTW THRESHOLD PROBABILITIES...

* High for ceiling 5000 ft or less today and tonight.

* Moderate for scattered thunderstorms this afternoon and evening.

PREV DISCUSSION... Issued at 350 AM EDT Thu Aug 6 2026

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.

DTX WATCHES/WARNINGS/ADVISORIES

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