textproduct: Detroit/Pontiac

KEY MESSAGES

- Mild and mainly dry today aside from a low shower or thunderstorm chance south of I-94.

- Above normal temperatures through the second half of the week.

- Additional chances for showers and thunderstorms Friday.

DISCUSSION

Broad deformation is in place across the Great Lakes this morning, with residual frontal convergence noted in surface observations (SW at DTW compared to NNW at MBS). The last of the frontal cloud band has exited to our east, with clear skies observed across the CWA this morning. Some patchy fog is possible toward daybreak given the efficient radiative cooling conditions, although observations have shown limited coverage thus far.

Surface high pressure slides across the northern Great Lakes today, keeping most of SE Michigan mild, sunny, and capped. The exception to this is near the Ohio border where the aforementioned front is expected to stall further north than in previous model runs. Model signal generates enough 925-700mb ascent and moisture convergence along this frontal zone to erode the existing cap across the far south. Did add chance PoPs to align with the wedge of instability that models are generating this afternoon, although still have pause for convection reaching this far east given how dry the column is. SWODY1 has designated a General Thunder risk for SE Michigan. Mid- level height rises then expected tonight-Thursday as longwave ridging is pushed east by an expansive upper low west of the Mississippi. Maximum h5 heights of 570-572 dam move overhead at peak heating Thursday, pushing daytime highs into the mid-upper 70s through the end of the work week. Column stability and lack of moisture supports another generally dry day Thursday.

The next opportunity for broad coverage showers and thunderstorms arrives Friday-Saturday, orchestrated by the deep western CONUS closed low. This low is currently off the Pacific Coast, and will struggle to phase with a second northern stream wave until Thursday night. Broad synoptic forcing across the eastern Plains leads to upscale growth along the occluded front Thursday night, not reaching SE Michigan until Friday evening. By the time this happens, the wave and surface reflection will be actively breaking away from the parent low. Forcing and moisture become more disjointed during this process, and instability/shear parameters become less favorable for organized convective potential. That said, if the surface low tracks directly overhead that would augment ascent and low level wind shear profiles. SWODY3 designates General Thunder during this period. Ensemble member interquartile range for QPF ranges between 0.25" to 0.75".

High pressure fills in aggressively behind the front Saturday-Sunday marking a return to drier conditions. Daytime highs in the mid to upper 60s this weekend will be closer to normal late April standards.

MARINE

A weak cold front settles south of Lake Erie this morning and inbound high pressure allows north wind to gradually diminish through the day. Benign marine conditions prevail through tonight and into early Thursday. The next low begins to take shape over the northern Plains today, eventually sending the front back north as a warm front late Thursday into Friday. This brings moderate southeast flow and the next chance for showers and storms. The best chance for thunderstorms and gusty southeast to east wind will be Friday night into Saturday morning as low pressure moves in along the front. Another area of high pressure then builds in later this weekend.

PREV DISCUSSION

Issued at 1127 PM EDT Tue Apr 21 2026

AVIATION...

A cold front will move from north to south across Se Mi overnight. This front will largely be dry, marked by a wind shift to the NNW. Some subtle low level moisture in the post frontal environment may support a brief intervals of MVFR based fog or a few to scattered low clouds in metro Detroit where moisture quality will be a little better. High pressure expanding into the region Wednesday will support light winds with just a few high based afternoon cu.

For DTW/D21 Convection...None.

DTW THRESHOLD PROBABILITIES...

* None.

DTX WATCHES/WARNINGS/ADVISORIES

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