Area Forecast Discussion

KEY MESSAGES

- Isolated showers and thunderstorms this afternoon-evening. Additional showers and perhaps a thunderstorm clip the area tonight. An isolated strong storm capable of damaging winds is possible in either timeframe though overall potential is low.

- Better chances for storms Monday evening ahead of an approaching cold front. A few severe storms producing damaging wind gusts are possible.

- More seasonably average airmass returns for midweek.

DISCUSSION

Heat and humidity have returned today with most of the area now seeing temps in the upper 80s and dewpoints in the upper 60s. Model advertised elevated warm layer was sampled by the 12Z KDTX RAOB at 725mb providing a modest cap to convective potential this evening. While CAMs suggest around 1000 J/kg of both SB/MLCAPE available late day, they struggle to overcome said cap and generate much more than an isolated pop-up shower/storm. Afternoon radar trends appear to confirm this with only isolated pop-up light showers thus far. As such, its more likely that the vast majority of the area stays dry this evening. The conditional severe chance if any updraft can break through the warm layer is likewise low this evening as column winds below 700mb hold aob 20kts confining the bulk of shear above 3km. For the late evening-overnight period, there has been notable convergence amongst high-res models in the CAPE gradient failing to cross Lake Michigan, instead stalling along the WI shoreline. This results in developing MCS(s) over the western Lake Superior basin to exhibit a due south drift in track along Lake Michigan entirely missing SE MI (aside from perhaps some light trailing stratiform showers clipping portions CWA). While the forecast tonight will still keep a slight chance (15-20%) mention for rain, severe chances are now looking to be minimal.

How exactly Monday panes out will depend on the progression of tonight's storms over the western Great Lakes, in large part their affects on the CAPE gradient. With the current favored scenario of a Lake Michigan track, this effectively pinches off southern lower MI instability confining main reservoir to WI/IL Monday. With weak lower level winds still in place, advection of this gradient east is slow, not reaching central southern MI until Monday late afternoon pushing the main local convective window back towards ~22-00Z. Still a good spread in outcomes wrt to the robustness of said convection however given the stronger synoptic setup (ie mid-level trough digging into the central Great Lakes and an associated surface cold front dropping south) would expect at least scattered thunderstorm coverage locally. For severe potential, forecast soundings show only marginal improvements in low level winds relative to today (~5kt increase) again confining the majority of shear around/above 3km. Magnitude of available instability is still uncertain given the dependency of advection, but shear profile does not lend confidence in severe storm chances.

MARINE

Still opportunity for isolated/scattered showers/thunderstorms to go up the rest of the evening and tonight, as the Central Great Lakes resides on the outer fringe of a very strong upper level ridge centered near the Four Corners region. A low pressure system then tracks across the northern Great Lakes during Monday. Thunderstorm activity continues to increase in coverage and intensity with this system, especially along the trailing cold front that brings a chance of severe thunderstorms as it moves through the region. Outside of storms, wind and waves are low until the northerly wind shift post front late Monday night into Tuesday when speeds likely reach 25 to 30 knots over southern Lake Huron. Small craft advisories will likely be needed as elevated waves build over the southern Lake Huron Basin. Winds slowly diminish on Wednesday as large area of high pressure over the Western Great Lakes slowly advances east, arriving on Thursday. This will assure dry conditions for those days.

HYDROLOGY

Convective rainfall chances will increase Monday afternoon and peak Monday evening. Locally intense rainfall rates will be possible with any convection. There is the potential for a couple rounds of showers/thunderstorms over some areas during this time period. Probabilities for a quarter to one inch of rain are moderate to high. The chances for locations to exceed an inch are low (less than 20 percent) at this time.

PREV DISCUSSION

Issued at 227 PM EDT Sun Jul 26 2026

AVIATION...

Convection is trying to emerge this afternoon, fighting a persistent capping inversion near 7 kft AGL. This has kept conditions mainly dry through 18Z, with only narrow diameter short-lived showers cropping up. Expect continued diurnal heating and destabilization to eventually break the cap allowing some isolated storms before nightfall, moreso from PTK south. Kept a PROB30 due to the conditional nature of thunderstorms emerging. Mainly quiet tonight with low-mid level VFR cloud cover expected ahead of another possibly unsettled day on Monday. Upstream storm complex could be ongoing and approach MBS early Monday morning. A lull is then expected for the rest of the morning hours before convective chances return Monday afternoon. Once again, the timing and low predictability setup limits thunder mentions to a few additional PROB30 groups (MBS and DTW, the latter being after 18Z). VFR conditions are generally expected to hold through the TAF period during dry weather.

D21/DTW Convection...A low chance remains for a thunderstorm or two this evening (30 percent). A nocturnal thunderstorm complex is now more likely to stay northwest of the airfield early Monday morning. Additional isolated to scattered storms are possible Monday afternoon.

DTW THRESHOLD PROBABILITIES...

* Low for ceiling at or below 5000 feet through this evening.

* Low for thunderstorms this evening, Monday morning, and Monday afternoon/evening.

DTX WATCHES / WARNINGS / ADVISORIES

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