textproduct: Detroit/Pontiac

KEY MESSAGES

- Rain and thunderstorm chances continue through the midweek period.

- The weekend indicates showery weather but mild temperatures Saturday and Sunday.

DTW THRESHOLD PROBABILITIES

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

* Low for thunderstorms this morning.

PREV DISCUSSION

Issued at 300 AM EDT Wed Sep 16 2026

DISCUSSION...

Very strong H5 599 dam mid-upper level high pressure over Southeast US will slowly retrograde to portions of east Texas and OK by Friday. The upper level jet axis over eastern Canada will be slow to move which will keep the baroclinic zone in relatively close proximity to Southeast Michigan through at least the end of the week and beginning of the upcoming weekend.

For today, plan view perspective of thetae shows the near surface extension of the frontal zone slipping southward to the Ohio border while the 900-700mb frontal surface remains farther north between the I 96-I 69 corridors. Differences exist with regards to the north south extent of shower/convective development later today. Consensus of many of the models including NAMnest and HRDPS initiates deep convection to the south of IN/OH state line, whereas the ECMWF brings QPF (from weaker elevated showers) much father north through much of Southeast Michigan. System relative flow trajectories highlight a coherent 925-850mb cyclonic circulation emerging today near South Bend that will track eastward increasing convergence. Models suggest shower activity approaching after 14z with spotty activity in an around the area this afternoon. Out of respect for the elevated portion of the frontal zone and the progged convergence, will keep inherited broad brushed PoPs.

Despite little north to south movement of the upper level jet axis, the entrance region and confluence aloft will support stable surface high pressure late Thursday and Friday. Strong likelihood that increasing anticyclonic flow trajectories will result in lower dewpoints into the 50s. A comfortable couple of days.

Right entrance region to very large jet entrance brings the potential for upstream convection to ride eastward through Lower Michigan. There has been a subset of solutions that have a MCS developing over the Plains states Friday and arriving over Southeast Michigan midday Saturday. Breadth of synoptic scale forcing with time of year suggests heavy rainfall potential. The latest Excessive Rainfall Outlook products have been highlighting a Slight risk for a good portion of Southeast Michigan. Given the structure an organization of the thetae ridge a wave will act upon, the setup looks good. The current forecast as 80-90% PoPs for Saturday. Another trough structure does look to suppress heights and cause a cold front to slip southward for Sunday.

MARINE...

A weak cold front gradually settles across the southern Great Lakes this morning, shifting wind direction to north and northeast in its wake with brief gustiness to around 15-20 kt over Lake Huron. High pressure passes across the northern Great Lakes today, favoring lighter winds and dry weather through the afternoon. The cold front stalls near the southern Great Lakes this evening, sustaining a chance for showers and storms mainly near Lake Erie into tonight and Thursday. The gradient strengthens Thursday evening as another area of high pressure builds into northern Ontario, producing an uptick in northerly winds early Friday morning. Given the long fetch into southern Lake Huron, will monitor the need for a Small Craft Advisory for high waves reaching the nearshore waters Friday morning.

DTX WATCHES/WARNINGS/ADVISORIES

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