textproduct: Detroit/Pontiac

KEY MESSAGES

- Morning showers with isolated thunderstorms dissipate, then thunderstorm chances rise again this afternoon; potential exists for isolated damaging wind gusts. - Dry Friday except for a chance of a few evening showers near the Ohio border.

- Warmer and dry this weekend.

- Very hot and humid conditions are likely through the first half of the next week as heat indices could exceed 100F; some opportunities exist for thunderstorms.

DTW THRESHOLD PROBABILITIES

* High for ceiling at or below 5000 ft this morning, low by afternoon. * Low for thunderstorms early afternoon through early evening.

PREV DISCUSSION

Issued at 359 AM EDT Thu Jun 25 2026

DISCUSSION...

Updrafts within nocturnal convective showers positioned along the elevated instability gradient have largely failed to intensify early this morning. This has led to very limited lightning activity with both the initial and secondary loosely organized shower lines. Low- end potential still exists for a few more rumbles of thunder through the first half of the morning given antecedent conditions.

For the daylight hours, a mature surface low reorganizes as it comes ashore over eastern Lake Michigan, tracking across central Lower Michigan throughout the day. Meanwhile, sustained moisture transport leads to rising instability as the day progresses, at least for portions of the forecast area. Weak residual capping should erode between 17Z and 19Z, and once it does, equilibrium levels could extend all the way to the tropopause. Latest HREF, RRFS, and local probabilistic data support instability metrics nearing 1 kJ/kg during the diurnal maximum this afternoon, although moisture quality issues may develop along/south of I-94. Highest 0-6 km bulk shear located south of M-59 still appears displaced from the better instability to the north. Regardless, expect a better convective response from the Tri-Cities, across The Thumb, and southward toward Metro Detroit. Overall coverage with this marginal event will be isolated to scattered, but some organized storms still pose a low- end isolated severe wind threat. Latest SPC Convective Outlook did include a small Marginal Risk area tied to the potential for a few discrete stronger cells, but the bulk of Southeast Michigan that sees storms later today should be sub-severe. High temperatures will vary from north to south, with better chances to end a 12-day streak of sub-80F MaxTs across the southern portion of the area. This occurs, in part, due to lower cloud cover and increasingly sparse convective coverage. The system's cold front should be departing between 21Z and 00Z, so subsidence should take over and quickly suppress late evening activity after the boundary-layer decouples. Upper Midwest high pressure builds in behind the low overnight with mainly dry conditions expected.

Damping shortwave ridge works over the Great Lakes on Friday while a low amplitude embedded trough originating from the Four Corners lifts into the Ohio Valley. Most guidance now keeps all of Southeast Michigan dry as the cyclonic wave's rain shield approaches the Michigan/Ohio border, attributed to extensive column dryness and weak ENE flow in the lowest 3 kft. Cannot fully rule out parts of Lenawee and Monroe Counties getting clipped by some brief showers (or perhaps just virga) Friday evening (see NAM 3 km and 12 km). Dry across the rest of the forecast area with temperatures slightly below normal with Lake Huron modification.

High pressure influence persists over the weekend with mainly dry conditions and thermal moderation as height rises commence within the backdrop of major longwave pattern changes for central and eastern CONUS. Continental ridge amplification becomes much more pronounced by early next week as the 500 mb geopotential height center spikes above 597 dam near the confluence of the Mississippi and Ohio Rivers. The composite ridge axis will drift slightly eastward mid-week making Tuesday and Wednesday the hottest days of next week. Air temperatures should have no trouble reaching 90+ degrees, and with a positively tilted progressive Pacific Northwest wave getting steered back into southwestern Canada, a confluent low- level jet tracing back to the Gulf will usher 70F dewpoints into southern Lower Michigan. Expect heat indices to easily break 100F if current trends hold as expected; therefore, heat-related headlines will probably be needed. Convective potential persists in both the possibility for MCS longevity and perhaps surface-based free- convection.

MARINE...

A weak low pressure system will continue it's slow trek across central Lower Michigan through this afternoon. This brings the potential for some rain showers, potentially even some thunderstorms, throughout this period. Winds are expected to be relatively calm due to the overall weak pressure gradient of this low pressure system. If any thunderstorms were to develop during this time period they would be capable of locally higher wind gusts. After this system departs to the east, a high pressure system is expected to develop over our region throughout the weekend, bringing warmer and calmer weather along with it.

DTX WATCHES/WARNINGS/ADVISORIES

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