textproduct: Detroit/Pontiac

KEY MESSAGES

- Showers and a rumble of thunder late tonight and Sunday morning precede the beginning of a new warming trend that holds for the bulk of next week.

- Southwest wind gusting in the 30-40 mph range develops Sunday afternoon helping to lift temperatures into the 70s.

- The pattern also becomes active for periods showers and thunderstorms Sunday night through Wednesday.

- There is a Marginal Risk of severe thunderstorms Monday night and Tuesday morning.

- Locally heavy rainfall potential also increases during the mid week period.

DISCUSSION

A postcard early to mid April Saturday afternoon is in progress as high pressure controls conditions across SE Mi. It brings in a cool and dry air mass that needs full sun to finish lifting high temperatures just to near normal values in the lower to mid 50s. Readings struggle to climb out of the 30s near Lake Huron with a light onshore wind component setting up the standard cooler near the Lakes exception.

Upstream observations across the Midwest this afternoon preview changes that get underway in the Great Lakes tonight leading to increasing coverage of rain showers toward sunrise. Progression of larger scale 500 mb structures shifts surface high pressure quickly to the Atlantic coast while the next low pressure center organizes in the Dakotas. This low interacts with the stalled TN valley front to rapidly accelerate moisture transport and isentropic ascent into Lower Mi during the night, although greater coverage and intensity of the resulting showers/rumble of thunder develops toward the northern Great Lakes aligned with the low level jet maximum. Model soundings also show dry air lingering below 850 mb that at least pushes back against intensity toward the Tri Cities, and both intensity and coverage toward metro Detroit. Near categorical POPs along and north of M-46 are Ok for coverage while leaning toward the lower end of the QPF guidance range, generally less than 0.25 inch before the pattern shifts north by afternoon.

The rest of Sunday sees advancement of the warm sector into Lower Mi during the afternoon and evening. The key here is the parent surface low deepening well north toward the MN arrowhead which helps veer the wind SW and drive the warm front northward against the cooler Great Lakes aggregate. A stray shower or thunderstorm could originate off the surface to mid level theta-e ridge nearby to the west and affecting mainly the Tri Cities as model soundings indicate some afternoon surface based CAPE. Scattered to broken clouds are more likely over the rest of SE Mi making gusty SW wind and warm temperatures the weather highlight. Hi-res model soundings support HREF mean gusts potentially in the 30-40 mph range which helps lift temperatures into the mid and upper 70s, and mainly from the I-69 corridor southward across metro Detroit.

For Sunday night into Monday, there appears to be a considerable MCV signal in today's 12Z models originating from southern Plains convection tonight and Sunday. A nocturnal convective increase is expected over Lower Mi as the theta-e ridge crosses the area Sunday night with a nocturnal/low level jet instability boost, however the forecast leans away from the higher end QPF totals in range of deterministic solutions. Blended guidance offering 0.25" to 0.5" late Sunday night and Monday morning looks more reasonable compared to totals exceeding 1 inch that rely on a mesoscale feature with low predictability.

The air mass gains an even greater summer feel after showers/storms decrease again Monday afternoon. Surface Td is projected to touch the lower 60s while high temperatures range from around 70 Tri Cities to mid/upper 70s metro Detroit. James Bay low pressure has a cold front extending through Upper Mi which settles into central Lower Mi Monday night and which is held in place by central Plains low pressure. The warm and humid air mass over southern Lower Mi then becomes capable of greater instability heading into Monday night and Tuesday morning, the SPC Day 3 general thunder/marginal risk time period tied to an area of slight risk in the Midwest. The outlook carries low predictability due to the changing position of the surface front and an expected transition from surface based to elevated convection, both of which are a moving target at this point in the forecast process.

The central Plains low pressure system keeps the mid week period convectively active as well. This system presents a somewhat rare Day 4 SPC outlook for Lower Mi is it tracks into northern Ontario Tuesday and Wednesday. The trailing cold front lingers nearby during the mid week period and also becomes the focus for heavy rainfall potential. Otherwise, daytime temperatures hold in the 70s with no real air mass change expected until closer to next weekend.

MARINE

High pressure center exits Lower Michigan this evening, heading toward the eastern Great Lakes overnight. Light and variable winds near the anticyclone will begin to organize south-southeasterly, amidst ensuing return flow. Gradual gradient constriction causes sub- 10 knot winds to rise tonight, exceeding 20 knots for the northern half of Lake Huron by sunrise Sunday. Expect a more active week of weather, beginning Sunday morning, as showers move in ahead of a decaying line of nocturnal thunderstorms. Locally higher winds and waves are possible as convection works across the Huron basin, but lower column stability should limit overall gustiness. Potential still exists for brief gusts to gales late Sunday into Monday as a 65+ knot low-level jet moves through the central Great Lakes. The main area of concern will be Saginaw Bay given funneling southwest flow, but it is possible that the stronger gusts extend further south into Lake St. Clair and western Erie, and/or The Straits. Several additional rounds of showers and thunderstorms are expected throughout the week due to a series of troughs, low pressure systems, and fronts.

PREV DISCUSSION

Issued at 107 PM EDT Sat Apr 11 2026

AVIATION...

High pressure governs conditions across lower Michigan this afternoon and evening, maintaining light easterly flow and SKC through tonight. Upper level moisture then moves into the region early Sunday morning, with a gradual build down of cloud bases toward 5.0 kft agl. A band of concentrated low level moisture then lifts into the airspace between 09z-13z along an elevated warm front, triggering showers and possibly a rumble of thunder mainly toward MBS/FNT. Less confidence in rain potential exists toward DTW where dry air may cause rain to evaporate before reaching the ground. This also places the best chance for a brief period of MVFR cigs/vsbys over the Saginaw Valley. The surface warm front then lifts into the airspace Sunday afternoon causing winds to veer to the southwest. Gusty winds and scattering low cloud are anticipated as the boundary layer destabilizes.

For DTW... there is a low chance for a rumble of thunder Sunday morning as a band of rain lifts into Lower Michigan. If a thunderstorm does develop, it is most likely between 09z and 13z.

DTW THRESHOLD PROBABILITIES...

* Low for ceilings below 5000 ft today. Moderate later tonight into Sunday.

* Low for thunderstorms Sunday morning, mainly between 09z and 13z.

DTX WATCHES/WARNINGS/ADVISORIES

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