textproduct: Detroit/Pontiac

KEY MESSAGES

- Much cooler temperatures and periodic shower chances rest of today through Friday.

- Temperatures drop into the mid-30s Thursday morning, possibly leading to frost development.

- Warmer this weekend with continued rain chances.

DTW THRESHOLD PROBABILITIES

* None

PREV DISCUSSION

Issued at 328 PM EDT Tue May 5 2026

DISCUSSION...

Broad longwave troughing governs the forecast over the next 7 days, supporting a showery pattern and below normal temperatures through the end of the work week. First instance of this is ongoing as the elevated remnants of a frontal zone slowly exit SE Michigan. Quicker pace of the front has displaced the highest rain chances to our south and east compared to previous forecasts, although a second wave of moisture over western Illinois may clip southern portions of the forecast area later this evening. This keeps rain chances going through late tonight for locations south of I-96. Cloud cover diminishes toward northern Lower Michigan away from the frontal zone, with the Saginaw Valley/Thumb on the northern fringe of the cloud shield. This has implications for radiative cooling overnight, as lows drop into the upper 30s to low 40s under a blanket of high cloud. If cloud cover can clear entirely, some areas may see patchy frost development (most likely for northern portions of Midland/Bay), but confidence is low in this outcome.

Thermal trough settles into the Great Lakes region Wednesday-Friday, drawing a pool of -5 to -10 C 850mb temperatures overhead. This leads to a period of below normal temperatures with daytime highs only reaching the upper 50s. Coldest temperatures are forecast to be Thursday morning (mid-30s) as the base of the trough coincides with the diurnal minimum and clearing skies. Frost/Freeze headlines will be considered in subsequent forecast updates. This period will also be characterized by multiple embedded shortwaves pivoting around the Hudson Bay upper low. Diffluent northwest flow initially keeps conditions dry Wednesday, even amidst synoptic ascent as one such wave glances across northern Lower Michigan and the left exit of a 155 knot jet streak surges in from the south. A stray shower cannot entirely be ruled out invof the vort max, but overall 5.0-18.0 kft agl dry layer should be sufficient in preventing widespread shower development. Combination of cold advection and the next embedded wave Thursday lead to steepening low level lapse rates (sfc-3km lapse rates exceed 7.0 C/km) and moistening mid levels to increase convective shower chances Thursday afternoon-evening. This wave train pattern continues Friday into the weekend, carrying periodic rain chances through the remainder of the forecast period.

The overall precipitation pattern offers low predictability given weak/transient forcing, disjointed moisture quality, and synoptic scale wave interactions. There is model signal for a cold front to track across the area sometime Saturday-Saturday night, which would provide a more focused opportunity for shower and thunderstorm chances. Depending on the timing of this front, temperatures could warm well into the 60s Saturday in the presence of warm and breezy warm sector flow. Ensemble members however still exhibit quite a bit of variance in both timing/placement of the forcing this weekend with a lot of details to work out before then.

MARINE...

A cold front is clearing the Central Great Lakes this evening, with cold air advection gradually filtering through over the next couple of days. Because the main low and tightest pressure gradient will reside near or over Hudson Bay, winds are expected to stay mostly on the light side (under 20 knots) for the rest of the work week. This pattern of clipper systems bringing periodic chances for showers will continue into the weekend as milder air and higher moisture levels arrive. As it stands now, this leads to Saturday night being the primary window for showers and isolated thunderstorms as a cold front slowly moves through the region.

DTX WATCHES/WARNINGS/ADVISORIES

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