textproduct: Detroit/Pontiac

KEY MESSAGES

- Dry end of the week conditions.

- Heat and humidity setting up this weekend and continuing through Wednesday. The potential exists for temperatures in the middle 80s Monday and Tuesday.

- Multiple opportunities for showers and thunderstorms with low confidence on timing and coverage of rain.

DISCUSSION

Amplified upper level pattern that has resulted in cool below normal conditions over the Great Lakes recently will persist for another 24 to 48 hours before shifting into an active, zonal northern stream for Southeast Michigan. Western periphery of closed 500mb low will squeeze to the east this evening allowing the center of a surface anticyclone to build overhead. Moderation of 850mb temperatures happens enough +3-6C tonight to keep low temperatures buoyed in the upper 30s to lower 40s. No Frost or Freeze headlines will be issued.

Pacific jet streak exit region and upper level low will impact Far Northwestern Ontario tonight and Friday. Absolute vorticity filament will extend to the south and push across the forecast area Friday afternoon. Thetae advection remains relegated to above 13.0 kft agl with strong static stability in the midlevels. High confidence in nothing more than virga or a rogue sprinkle. Highs Friday will reach around 70 degrees.

Zonal ridging will build rapidly over Southeast Michigan by the start of the day Saturday with high confidence the main warm front and baroclinic zone sharpens well to the north of Lake Superior and Lake Huron. Uncertainty exists with regards to the track and longevity of upstream convection and associated MCV as it tracks towards Southeast Michigan during the daytime Saturday. From this vantage point, greatest forcing will arrive in the form of moisture transport or thetae advection as an apex in deeper 850mb to 500mb thetae is directed through the area south of Saginaw Bay. A big question exists on timing of the convective wave as a subset of guidance (HRRR and hires GEM) suggests arrival at/around daybreak Saturday. The potential for strong or severe thunderstorms Saturday is not only dependent on the timing (morning vs afternoon) but also with the amount of debris cloud to limit destabilization in the lowest 6.0 kft agl. The latest Swody3 has Southeast Michigan designated as General Thunder, but it it something to monitor.

Strong energy in the Pacific Northwest will lead to downstream ridge amplification over the Great Lakes region beginning early Sunday and lasting through the early to midweek time period. Good signal exists amongst NWP that a broader LLJ exit region will force a secondary warm front through Lower Michigan Sunday. Low confidence on whether any convection will be able to survive over the area with indications an anticyclonic vorticity bubble will roll through the area during the daylight hours and enforce capping CIN in the 2.0 to 6.0 kft agl layer. With the most humid air of the season, the main narrative for Sunday through Tuesday becomes one of Summerlike conditions. The current data suggests surface dewpoints in the 60s Monday and Tuesday with heat indices well into the 80s (conditional to clouds). Will need to get closer to event time, but forecast soundings at this range suggest relatively lower mixing heights Monday that could put the lid on compressional warming, keeping highs more in the middle 80s rage. The upper level jet axis will then begin to push eastwards towards Lower Michigan that will eventually bring the area in target of upstream convection. Very low confidence exists on timing and duration of shower and thunderstorm activity late Monday through Wednesday. The current Day 5 Slight Risk that eclipses portions of the cwa appears dependent on the amount of convective instability that is being projected upstream over portions of Illinois eastward into Southwest Lower Michigan.

MARINE

High pressure drifts over the Great Lakes this evening, with northwest flow continuing to subside as the gradient relaxes. Flow then shifts to the south-southeast early Friday morning as the surface ridge moves east. Winds then become more organized through the day Friday, sustained around 15 to 20 knots by the evening as the next surface trough approaches the Great Lakes region. This system sends a wave of showers and thunderstorms into the area Saturday morning, with an unsettled pattern continuing into early next week as the surface trough washes out over the Midwest. Winds may become breezy at times through the weekend with gusts approaching 25 knots.

PREV DISCUSSION

Issued at 200 PM EDT Thu May 14 2026

AVIATION...

High pressure building into the area is resulting in widespread VFR conditions. Northerly winds are gusting into the 20 knot range which should go light and variable overnight as the ridge axis passes overhead. Some diurnal cu popped up this afternoon but should clear out this evening before cirrus starts streaming back in later tonight which will slowly lower through the day Friday.

D21/DTW Convection... No thunderstorms are in the forecast today through Friday.

DTW THRESHOLD PROBABILITIES...

* None.

DTX WATCHES/WARNINGS/ADVISORIES

MI...None. Lake Huron...Small Craft Advisory until 4 PM EDT this afternoon for LHZ441>443.

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