textproduct: Detroit/Pontiac

KEY MESSAGES

- Showers and thunderstorms this afternoon into the evening will pose a locally heavy rainfall and isolated damaging wind gust threat.

- Heat and humidity builds in Wednesday and Thursday. Afternoon temperatures are expected to reach the low 90s with heat indices potentially climbing into the upper 90s. A Heat Advisory may eventually be needed.

- Thunderstorms will be possible Wednesday and Thursday. The greater severe thunderstorm threat will be late Thursday/Thursday night with a Slight Risk in place for all of southeast Michigan.

- Not as warm and much less humid Friday through the weekend.

DTW THRESHOLD PROBABILITIES

* High for ceilings aob 5000 feet today and tonight. Medium Wednesday morning.

* Low in thunderstorms through 16z. Moderate between 16z and 02z this evening.

PREV DISCUSSION

Issued at 404 AM EDT Tue Jun 9 2026

DISCUSSION...

Mid level low pressure circulation will move across the Upper Peninsula today and drag a weak frontal zone across southeast Michigan this afternoon. A few showers/isolated thunderstorms are preceding this front this morning with the lead vorticity and thetae advection. The low level jet will help carry and an impressive moisture rich environment into the area today. PWATs from observed soundings last evening at ILX and DVN came in at 2.01 inches and 1.91 inches respectively. This airmass is arriving locally this morning along with the low 70s dewpoints being observed lifting into lower Michigan. The moisture and inbound front will support high PoPs across the area that increase this morning and carry into early evening. Favorable diurnal timing will yield CAPE values around 1500- 2000 j/kg helping support stronger updrafts. Limiting factors that will preclude a mention of a greater severe weather threat will be weak bulk shear at 20-25 knots and weak lapse rates. The warm cloud depths and moist adiabatic lapse rates point do point towards a greater heavy rainfall threat, which in turn brings potential for strong gusty winds from precip loaded downburst. Guidance continues to point towards pockets of 1-2 inches or greater of QPF that will be possible focused between 16Z and 04Z today. Confidence is low as to where these localized higher totals will possibly fall. Southeast Michigan remains in General Thunderstorms for the SPC Convective outlook for today.

Ridging will translate over the central Great Lakes Wednesday into Thursday. Increasing southwest flow will carry an even warmer airmass into the region with 850mb temperatures climbing to around 20C. This leads to an increase in surface temperatures reaching the low 90s. Add in the persisting humid airmass with dewpoints in the upper 60s to mid 70s and heat indices should approach 100 degrees and bring potential for heat headlines. The other concern for Wednesday will be the severe weather potential, which appears to be towards the later part of the day as a shortwave arrives on the heals of the passing ridge. Additional forcing from the increasing low level jet may be enough to trigger convection in the backdrop of greater subsidence and capping with the upper ridging. Tail end of the HREF suggests some convection is able to develop which would pose mainly a wind and hail threat. Strong instability (2000-3000 j/kg of MLCAPE) and steeper mid level lapse rates will be available, but shear remains lacking Wednesday evening. A Marginal Risk for all of southeast Michigan is in place for Wednesday.

A brief lull in precip looks possible Thursday afternoon with afternoon conditions remaining hot and humid with heat indices again approaching 100 degree. The greater severe weather threat is also slated for late Thursday and Thursday night. A strong wave will cross the western Great Lakes into Ontario and send a cold front through the region. Timing will be less favorable after peak heating, but models do offer enough instability with strong wind fields yielding good shear and more favorable lapse rates. This set up points towards a cold pool driven MCS along the front that would arrive locally pending the environment remains favorable. A Slight Risk for all of southeast Michigan is in place for Thursday.

The cold front sweeping through will drive the hot and humid airmass off to the east and bring more seasonable conditions for Friday into the weekend. Lower confidence forecast over the weekend as troughing holds over the Midwest brings low end precip chances. Afternoon temperatures by Sunday are forecast to be back down into the 70s and low 80s.

MARINE...

Weak low pressure tracks across Lower MI today and reaches Lake Huron late this evening. Scattered to numerous showers and thunderstorms will spread across the area with wind predominantly out of the southeast near 10 kt. Isolated storms may produce winds in excess of 34 kt. A warm and unstable air mass will take residence Wednesday and Thursday, bringing additional chances for showers and thunderstorms. Prevailing wind will be out of the west and southwest with potential for gusts upwards of 20 kt at times, especially over the shallower, warmer waters of Saginaw Bay, western Lake Erie, and Lake St. Clair. A cold front passes through the region on Friday and brings a brief period of drier conditions.

HYDROLOGY...

A moisture rich environment will pose a locally heavy rainfall threat today. While most ensemble members put QPF amounts generally within 0.25" to 0.75", the environment will be supportive of pockets of 1.00" to 2.00" rainfall amounts or greater. Highly variable amounts can be expected across southeast Michigan. Convective rainfall rates will have potential to reach 1.00" or greater at times, especially during the afternoon and early evening. Low confidence exists as to where these heavier pockets of rainfall would fall, but the environment will certainly support isolated flash flooding potential especially if it occurs over any urban areas or flood prone areas.

DTX WATCHES/WARNINGS/ADVISORIES

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