textproduct: Detroit/Pontiac

KEY MESSAGES

- Showers and thunderstorms will be possible Tuesday afternoon and early evening. Uncertainty exists on what the main threats will be, but damaging wind gusts to 60 mph, large hail to 1 inch, and an isolated tornado may be possible.

- Widespread rain and thunderstorms are expected Wednesday evening and Wednesday night. Heavy rainfall is possible which may lead to localized flooding, especially in urban areas. Some questions remain where the highest impact severe weather will track.

- Slightly below normal temperatures are expected for the end of the week and next weekend.

DISCUSSION

Upper level jet axis overhead of Southeast Michigan will bring an active pattern to Southeast Michigan throughout much of the period. Current forecast models advertise a high volume/amount of shortwave maxima that will come in proximity to, or outright eject through the state during the next 7 days.

Differential low level cold advection from last night has resulted in residual static stability today in the 6.0 to 8.0 kft agl layer. Hires runs suggest a very weak embedded shortwave pushing through late this afternoon. Low 40 degree dewpoints will limit coverage but just enough high based boundary layer growth to support a sprinkle or virga across eastern Metro Detroit. Temperatures will drop fairly quickly this evening with the setting sun. Lows are expected to be in the lower 50s.

Upper level jet impulse at 110 knots will dig into the basal portion of deeper Eastern North American troughing on Tuesday. Numerical models are in good agreement that a vigorous shortwave will dig across Wisconsin driving a lobe of vorticity farther east through Southeast Michigan. A Good pop of midlevel cooling between 8.0 and 14.0 kft agl will lead to MLCAPES of 500-1000 J/kg. Interesting solutions exist with regards to the most favorable timing for thunderstorm activity. There could be two lines or areas of convection, the first starting as early as 18-19z with prefrontal warm advection with a second line developing between 21-02z along the cold front. It is the trailing thunderstorm activity during the early evening that may have the greatest potential for strong to severe thunderstorms. 0-6km bulk shear values are forecasted to push 40-50 knots which will likely result in storm organization. Will need to monitor cell trends tomorrow with some limitation on instability (< 1000 J/kg) but all severe threats (damaging wind gusts to 60 mph, large hail to 1 inch, and an isolated tornado) may be play. The latest Swody2 has all of Southeast Michigan designated as a Marginal Risk for severe weather.

Dynamic upper level low pressure with deep flow inflection will track rapidly through Southeast Michigan Wednesday evening. A high end signal exists for synoptic scale lift with strong meridional moisture transport driven by +65 knot low level jet followed by direct absolute vorticity advection. Still some 60 hours out from the event so will need to monitor hiresolution datasets as they become available. Very strong shear profiles with instability does appear favorable for widespread severe weather. The one thing to consider is a subset of solutions exist that suggests best organized convection could favor areas to the immediate south and west of the forecast area. Lapse rate profiles and early forecasts of frontogenesis with this system suggests heavy rainfall of 1 to 2 inches will be possible in a very short period despite what could be very fast forward storm motions. The latest Swody3 has portions of far southern Lower Michigan in Slight risk for Severe Weather.

A good setup for system relative isentropic ascent is anticipated in the wake of the early Thursday system. Predominately dry weather is a good likelihood with temperatures in the 70s and dewpoints in the 50s.

MARINE

Drier conditions persist today as high pressure migrates across the Tennessee Valley, extending into the southern Great Lakes. This causes flow to back southwesterly tonight into Tuesday. The arrival of a low pressure system and it's attendant cold front lead to showers and thunderstorms for the central waterways Tuesday afternoon/evening. Latest models indicate convection should hold-off until 1 PM or later, but timing the conclusion is less certain. A brief break in activity ensues Wednesday as shortwave ridging quickly passes over the region, followed by a secondary stronger system Wednesday night into Thursday. More intense convection is possible with the second system, capable of damaging winds, and to a lesser extent, waterspouts and large hail. Seasonably strong gradient (non-thunderstorm) winds will accompany the low with prevailing speeds climbing above 25 knots as the center of the low approaches Lake Huron late Wednesday night. Gusts to gales are probable for some portion of The Lakes Wednesday night into Thursday, after shallow mixing profiles deepen slightly, and 40-50 knot flow materializes within the lowest 3 kft. Winds decline a bit and organize out of the west Thursday evening through Saturday, accompanied by additional chances for showers.

HYDROLOGY

Extremely efficient moisture transport directed across a warm front will provide for very strong lift across Southeast Michigan Wednesday evening and Wednesday night. The potential exists for 1 to 2 inches of rainfall in 6 hours or less with this system. Latest ECMWF ensemble guidance suggests the tail of the distribution on the high side is less than 2 inches. Expect this rainfall will result in rises on area rivers and may pose a flood risk to urban areas.

PREV DISCUSSION

Issued at 141 PM EDT Mon Jun 15 2026

AVIATION...

Low level instability and moisture is enough to develop a widespread cu field across the area this afternoon. Gusty westerly flow will relax this evening with the loss of daytime heating while backing to more southwesterly ahead of the next disturbance. Some mid and and high cloud will stream in tonight ahead of the next disturbance but all above 5kft. The southwesterly winds will become gusty tomorrow in advance of the system. There could be a few isolated showers in the afternoon but most or all of the convection will occur after 18Z, thus the end of the taf.

D21/DTW Convection...There is a low chance of isolated thunderstorms developing tomorrow afternoon, with increased chances after 20Z. Any thunderstorms that develops late would have the possibility of being strong to severe.

DTW THRESHOLD PROBABILITIES...

* Low for ceilings at or below 5000 ft through tonight. Moderate Tuesday afternoon.

* Low for thunderstorms before 20z Tuesday.

DTX WATCHES/WARNINGS/ADVISORIES

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