textproduct: Detroit/Pontiac

KEY MESSAGES

- Dry with seasonable temperatures this evening.

- Showers and thunderstorms move into the Tri Cities Wednesday, expanding across the rest of SE Michigan Wednesday night.

- An unsettled pattern continues Thursday into the weekend with periods of showers and thunderstorms likely.

DISCUSSION

Healthy coverage of diurnal cumulus this afternoon wanes in coverage through the evening as temperatures remain seasonable in the low 80s. Dry conditions persist overnight as the mid-level ridge axis slides east in favor of broad longwave troughing that lingers through the weekend. This brings a transition to a wetter pattern for the back half of the work week and possibly into the weekend.

The 12z KDTX RAOB sampled a very dry airmass with PWAT of 0.75", which will take a good deal of moisture advection to overcome before precipitation can reach the ground. This process begins over the Saginaw Valley late Wednesday morning, starting with an increase in high cloud followed by increasing PoPs through the afternoon. The rain shield stays anchored to a slow-moving cold front that eventually shears out to further limit its eastward progress through most of the day Wednesday. Meaningful progression of the rain shield into the Detroit Metro region thus holds off until late Wednesday night as one of several upcoming shortwaves ripples through the Great Lakes. Sharp delineation in rain chances/cloud cover sets up a sharp thermal gradient across the cwa, with upper 70s highs near Midland to upper 80s in the urban Detroit footprint.

More widespread rain chances emerge Thursday-Friday as return flow maintains a steady feed of low level theta-e into lower Michigan. This moisture will be repeatedly engaged during the period by a train of low amplitude perturbations. Ensemble QPF members through the end of the week generally fall around a half inch or less, although a handful of 1+ inch totals are in the solution space around the Tri Cities. A main limiting factor to higher end totals is the lack of strong convective component to this event, although there is still some uncertainty here that will depend on boundary layer conditions. Presence of the trough elevates mid level lapse rates toward 6 C/km through the end of the week, but otherwise the influx of mid level dry air and modest boundary layer conditions struggle to generate more than ~1000 J/kg MLCAPE at best. This is with highs right around 80 degrees Thursday and slightly warmer Friday. SWODY3 (Thursday) places SE Michigan in a General Thunder risk, while the slightly warmer/higher dewpoint environment could boost instability for Friday.

Unsettled pattern continues into the weekend with a strong ridge over the Four Corners region and an equally strong low over over Hudson Bay. Main shift this weekend though will be change in steering flow to the northwest, accelerated by confluence over the central CONUS between these two systems. While details are still fuzzy on coverage/timing, precipitation chances linger Saturday- Sunday.

MARINE

High pressure influence lingers across the central Great Lakes today as the center of the surface ridge slides across Appalachia into the Northeast. Southwesterly winds are still expected to rise through the afternoon hours given the return flow configuration and gradient enhancement as low pressure moves from northern Ontario into Hudson Bay. An attendant cold front approaches from the west and briefly stalls out over Lake Huron Wednesday. This provides the first opportunity for showers and a few thunderstorms this week. Several disturbances are then expected to ripple over the boundary, preserving rain/storm chances through Thursday. The front should resume forward progress on Friday with additional chances for convection for the southern waterways. Winds are expected to remain below headline criteria through the rest of the week. Drier weather may briefly return for parts of Friday and/or Saturday, but the front will stall out again in the vicinity, keeping low chances for thunder through the weekend.

PREV DISCUSSION

Issued at 136 PM EDT Tue Aug 4 2026

AVIATION...

VFR conditions prevail under high pressure. FEW-SCT cu between 4kft - 6kft persists for the next several hours before waning due to dry air entrainment and reduction in daytime heating. Light winds and VFR conditions continue overnight.

D21/DTW Convection...No thunderstorms expected.

DTW THRESHOLD PROBABILITIES...

* None

DTX WATCHES/WARNINGS/ADVISORIES

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