textproduct: Detroit/Pontiac

KEY MESSAGES

- Very warm or hot and humid conditions develop Tuesday and Wednesday, though cloud cover and storm potential introduce uncertainty into peak daily temperatures and heat indices.

- Periodic chances for showers and thunderstorms continue through much of the week. Tuesday carries a Marginal Risk for severe weather, with Wednesday carrying a Marginal to Slight Risk.

DTW THRESHOLD PROBABILITIES

* Low in thunderstorms this evening. Low on Tuesday.

PREV DISCUSSION

Issued at 321 PM EDT Mon Aug 31 2026

DISCUSSION...

Southeast Michigan will remain on the outer fringe of a strong upper level ridge (~597 DAM at 500M MB) centered over Kentucky/Tennessee Tuesday-Wednesday. This presents a challenging temperature forecast as clouds and convection could impact the maxes, as they have done the past couple of days. High-res models are continuing to struggle with the extent of showers and thunderstorms, and preference was to include a low chance of showers and thunderstorms tonight and tomorrow. A shortwave is tracking through the Midwest this afternoon and will round the weak ridge axis in place across western/central Great Lakes tonight. There is a good 850-700 MB Theta-E ridge/deep moisture axis straddling the southern Michigan border, and with another subtle moisture surge late tonight along and south of I-94 corridor. At the very least, would expect some convective debris lingering through the morning hours, which raises concern the max temps make not make it into the lower 90s and will end up closer to 90 degrees. Thus, confidence was not high enough to issue a Heat A advisory for the possible heat indices of 95-100 degrees. Some drying and warming in the mid levels is expected tomorrow afternoon, which should serve as some semblance of a cap, though it is still not totally clear if it will hold completely. If a remnant boundary or lake breeze is able to get something going, isolated severe storms are possible with MLCAPE of 2000+ J/kg advertised and favorable 0-6 KM bulk shear of 40+ knots. Both severe wind and hail possible with the high degree of instability and updraft strength.

Meanwhile, a seasonably strong upper level low is tracking through central Canada and will slowly fill as it tracks through northwest Ontario late tomorrow. Uncertainty remains on how well it will drive a surface frontal boundary meandering over the Great Lakes region south. Upper level disturbance(s) coming out of the Four Corners region look to arrive into the western/central Great Lakes Tuesday night and especially Wednesday. Exact timing will be important for severe chances, and SPC day 3 Outlook continues to highlight a Slight Risk for severe storms. Bulk shear will be very high, and there is a legit chance for convection to develop Tuesday night into Wednesday morning, once again impacting maxes and severe chances. There still is not enough of a southward push to the front for Thursday, so a renewed round of showers and thunderstorms remains possible as the ridge axis builds back over the Mississippi River Valley to end the workweek.

MARINE...

Low pressure system over southern Manitoba has an occluded front reaching down into northern Minnesota with a warm front then extending east through the straits and northern Lake Huron. A series of mid level disturbances have been initiating rounds of showers and thunderstorms which will continue to occur through Wednesday until the cold front drops through. Any break in the rain will be short lived as the front lifts back north on Thursday providing additional chances of storms. Winds will be fluctuating alot this week with the frequency of frontal passages. The weak gradient will keep speeds down through the week though with max wind gusts rarely touching 20 knots. The slightly cooler air over the waters brings chances of waterspouts with any of the storms over the lakes this week.

DTX WATCHES/WARNINGS/ADVISORIES

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