textproduct: Detroit/Pontiac

KEY MESSAGES

- Dry weather and cooler but seasonable temperatures move in for the weekend.

- Showers and thunderstorms return Monday night into Tuesday.

DTW THRESHOLD PROBABILITIES

* Low for thunderstorms this evening.

PREV DISCUSSION

Issued at 403 PM EDT Fri Apr 24 2026

DISCUSSION...

The ongoing band of thunderstorms crossing Lower Mi is the first phase of convection on schedule to affect the area this afternoon and this evening. It increased coverage and intensity on the leading edge of inbound short wave height falls and within an uncapped boundary layer with building instability. Mid afternoon hourly mesoanalysis indicates SBCAPE running up near 2000 J/kg with entry level bulk shear around 25 kts. Model soundings also continue to indicate narrow CAPE density and high moisture content within an HREF mean PW axis reaching up to around 1.5 inches. The CAPE/shear combination is proving capable of supporting some linear organization within multicell clusters that present a precip loaded downburst damaging wind threat through late afternoon. Some weakening is likely as activity reaches the mid Thumb region to Lake Huron on the leading edge of the instability axis.

The second phase of convection comes in with lower intensity in reduced instability between the leading line and cold front. Coverage is boosted by the cold front and smaller scale mid level wave hinted at in satellite imagery. This activity ends up sub severe while adding rainfall to event totals until the front sweeps activity eastward around midnight.

The weekend starts out dry but cloudy as the surface low center reaches the east end of Lake Erie by morning and has a trough extending back west into Lower Mi. This keeps the central Great Lakes mired in low clouds augmented by the Great Lakes that are trapped in and near the trough and under a strengthening mid level ridge. The associated subsidence inversion is maintained Saturday night while the low level wind becomes more neutral and less supportive of cloud maintenance, however direction veering easterly keeps SE Mi on the cloud edge to the south with lower predictability into Sunday. Confidence in dry weather through the weekend is much higher as model agreement is solid on maintenance of the 500 mb ridge over the central Great Lakes. The larger scale surfaced high pressure is also shown with good model agreement centered on northern Ontario and Quebec. The NE to E wind trajectory favors temperatures around late April normals in the mid 50s to mid 60s with onshore wind direction bringing the usual much cooler conditions near Lake Huron.

Dry weather holds to start the week on Monday while the next low pressure system organizes across the Plains states. It sends a band of showers and thunderstorms into Lower Mi Monday night as considerable system deepening occurs in the lee of the Rockies. Low level jet driven moisture transport consists of a Gulf modified continental air mass, but the size and strength of the low pressure system makes efficient use of the moisture/instability. The trailing cold front then sweeps showers eastward by Tuesday morning and leaves dry weather and near normal temperatures for mid week.

MARINE...

Cold front crosses the central Great Lakes this evening generating a broken line of showers and thunderstorms. An isolated storm could be strong to severe with wind gusts over 34kts being the main hazard. Secondary low center on the southern portion of the front crosses the southern lower MI tonight setting up modest northeasterly flow in its wake (peak winds up near 20kts). High pressure then expands over the Great Lakes over the course of Saturday before eventually departing first part of the day Monday. Light winds gradually take hold as this high becomes established as well as bringing drier weather for the weekend.

HYDROLOGY...

A band of thunderstorms leads a cold front across SE Mi this afternoon and evening. Two phases of activity combine for basin average rainfall amounts in the range between 0.25 and 0.75 inches, although localized amounts of 1 to 2 inches are possible for any areas that see repeated rounds of storms. Ponding of water on roadways and minor rises on streams and rivers will be the main impacts followed by localized minor flooding in urban and low lying areas.

DTX WATCHES/WARNINGS/ADVISORIES

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