textproduct: Detroit/Pontiac

KEY MESSAGES

- Low chance remains for isolated evening showers or thunderstorms, south of a line from Howell to Grosse Isle.

- Temperatures return closer to late May normals Thursday through the weekend, with the exception of a brief warm-up Friday.

- After today, the only chance for rain will be late Sunday into Monday morning.

DISCUSSION

A weak backdoor cold front slows from southern Lower Michigan into the northern Ohio Valley. Several competing synoptic factors will affect the development of conditional isolated afternoon showers and thunderstorms for portions of Southeast Michigan. A positively tilted shortwave trough embedded within northern stream flow descends on the region, overcoming the blocking influence of an anticyclone anchored over the central Atlantic. Poor model consensus exists regarding instability through the rest of the afternoon, as large dewpoint depressions inhibit destabilization. The highest potential for convective initiation will be located in the vicinity of the frontal slope where dewpoints of 60F are still possible. Tall and skinny CAPE profiles with an inverted-V shape below 5 kft (DCAPE in excess of 700 J/kg) lead to a low-end wind threat should sufficiently deep updrafts arise. The lack of moisture and shear limit the intensity and coverage of storms, should any arise. Based on the latest frontal positioning, any convection that materializes should be confined to points near and south of a line from Howell to Grosse Ile. Anomalous high temperatures repeat today, in the lower 80s outside the Lake Huron shadow, or about 10F above normal. Loss of daylight quickly diminishes any thundershower activity, followed by post-frontal cooling and further drying overnight.

Lower Michigan will reside within the proximity of the inflection point of the northern stream jet Thursday morning with gradual mid/upper height rises building throughout the day. A ridge axis marked by 500 mb heights of 585+ dam centers between Manitoba and Florida, remaining nearly stationary into the weekend, while troughing lingers over northeastern NOAM. Encroachment of warmer air aids in lifting/mixing 850 mb temperatures into the teens (Celsius) Friday, before the thermal gradient drifts back toward the west. Highs in the 70s are then expected to continue through at least the first half of next week as the pattern remains locked-in. Near-zero PoPs Thursday through Sunday with high pressure parked squarely over the state. Some semblance of an opportunity for rain late Sunday into Monday as a zonally oriented trough axis descends due-south from Hudson Bay, triggering nocturnal ascent amidst weak Theta-e advection from the Upper Midwest. Medium-range deterministic/ensemble/ML/AL models very in generating QPF with this setup.

MARINE

As high pressure expands from northern Ontario into Lake Superior tonight, there will be an increase in the north-norhteast winds across the eastern lakes. Wind gusts will reach or exceed 20 knots in the warmer nearshore waters. This will boost wave heights, leading to hazardous conditions to small craft. Winds and waves will decrease late Thursday into Thursday night as the surface high gradually sinks southward into the Ohio Valley by Friday. A weak surface cold front will then push across Lake Huron Friday night, in advance of another strong high pressure system. This may result in another period of hazardous small craft conditions in the nearshores.

PREV DISCUSSION

Issued at 1258 PM EDT Wed May 27 2026

AVIATION...

The weak front across southern Lower Mi is pausing southward progress as a trailing mid level wave catches up from the upper Midwest this afternoon. The wave and front combine to maintain a chance of showers along the terminal corridor, mainly after 21Z until daytime instability fades by mid evening. There is a better chance for greater shower coverage toward DTW where the front is still overhead or nearby to the south during late afternoon, however thunderstorm coverage and duration is still too limited for a place in the forecast. Conditions are otherwise VFR through tonight as the frontal zone is free of low clouds and the upstream northerly flow is so far not activating sub 5000 ft cloud development. This leads into a brief time window for a stray pocket of MVFR stratocu after sunrise that quickly mixes out or up into scattered shallow cumulus in a strengthening NE wind field by Thursday afternoon.

D21/DTW Convection... A weak front maintains a slight chance for a thunderstorm late this afternoon and early evening.

DTW THRESHOLD PROBABILITIES...

* Low for an isolated thunderstorm mainly 22-02Z.

DTX WATCHES/WARNINGS/ADVISORIES

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