textproduct: Detroit/Pontiac

KEY MESSAGES

- Showers and thunderstorms tonight and Tuesday will pose a locally heavy rainfall threat. The potential exists for isolated damaging wind gusts with any thunderstorm activity Tuesday afternoon and evening.

- Heat and humidity will build over Southeast Michigan for 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 most likely timeframe for organized severe thunderstorms may be late Thursday as a cold front approaches the area.

- Not as warm and much less humid Friday and next weekend.

DTW THRESHOLD PROBABILITIES

* Low in ceilings aob 5000 feet tonight. High Tuesday.

* Low in thunderstorms overnight and Tuesday morning. Moderate Tuesday afternoon.

PREV DISCUSSION

Issued at 305 PM EDT Mon Jun 8 2026

DISCUSSION...

Deep column high pressure will build out of the eastern Great Lakes towards the Eastern Seaboard tonight. In response, gradient flow will steadily veer to the south by Tuesday. The main narrative over the next 24 to 36 hours will be rich thetae advection into the forecast area that will cause PWATS to climb toward 2.00 inches. Surface dewpoints on Tuesday are expected to be in the low 70s. Scattered, high based shower chances begin this evening with lead spoke of absolute vorticity lifting into the area. Modest cooling above 12.0 kft agl should result in weak elevated instability that could support a shower or rumble of thunder. Static stability in the lowest 8.0 kft agl will limit any strong thunderstorm threat today.

Warmer and much more humid for Tuesday. Old, convectively augmented low pressure circulation will drift slowly eastward from southern Wisconsin through northern Lower Michigan and the northern Lake Huron basin. Southeast Michigan will be situated solidly within the moisture transport axis for the first half of the day before a weak cold front feature pushes across between 20-04z. Projected CAPE values Tuesday afternoon are expected peak in the 1750-2250 J/kg range with 0-6km bulk shear 25 knots. Low shear limits convective organization and convective vigor potential but high PWATS suggests wet microbursts and water loading possibly leading to an isolated damaging wind gust threat between 19-04z time window. A bigger threat may be isolated flooding potential with heavy downpours. The latest SPC Day 2 Outlook has Southeast Michigan designated as General Thunderstorm.

A longwave ridge will expand in wavelength while centering over the central Great Lakes Wednesday and into at least the first part of Thursday. The associated geopotential thickness increase will result in another uptick in surface temperatures reaching 90 degrees or more for Wednesday and Thursday with heat indices well into the 90s and potentially making a run at 100 degrees. Heat headlines may be needed. 800-600mb lapse rates are forecasted to be steep enough to result in SBCAPE reaching 3000 J/kg. From a dynamics perspective model signal supports larger scale subsidence and capping with the ridge parked overhead and episodic anticyclonic vorticity advection timed out for both midday periods Wednesday and Thursday. The low confidence portion of the forecast hinges on the subsequent tracking of any upstream MCS tracking towards Lower Michigan. The important note for Wednesday is 0-6km bulk shear values at 20 knots or less for the entire period bringing question to whether or not convection will be organized if it does make a run at Southeast Michigan. The latest Swody2 has a Marginal risk designation merely brushing up again Southeast Michigan. The period of most concern for strong to severe thunderstorms may be Thursday evening and Thursday night as the upper level trough advances towards the state. Models support stronger wind field aloft and kinematics finally arriving late with 850mb winds climbing above 50 knots. The latest Day4 Outlook for SPC has Southeast Michigan designated as 15% for severe thunderstorms. More seasonable weather conditions look likely for Friday and the upcoming weekend as a cold front sweeps out the humidity.

MARINE...

High pressure over New England migrates to the Mid-Atlantic this evening, maintaining southeast wind on the order of 10 kt into tonight. Weak low pressure tracks into southern Lake Michigan on Tuesday before passing across Lake Huron Tuesday night. This brings in a humid air mass with scattered to numerous showers and thunderstorms during this period. Winds will carry a degree of variability as the low tracks through, but remain around 10 kt outside of any localized higher gusts within storms. A warm and unstable air mass will take residence Wednesday and Thursday, bringing additional chances for showers and thunderstorms. Flow will be predominantly out of the west and southwest with potential for gusts upwards of 20 kt at times.

DTX WATCHES/WARNINGS/ADVISORIES

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