textproduct: Detroit/Pontiac

KEY MESSAGES

- Scattered light showers this morning.

- A short-lived dry period is expected tonight and Friday.

- Widespread showers return in earnest Saturday into Saturday night. Rainfall totals in excess of half an inch are likely, with the potential for 1 inch or more.

DTW THRESHOLD PROBABILITIES

* High for ceiling 5000 ft or less today and this evening.

PREV DISCUSSION

Issued at 316 AM EDT Thu Sep 17 2026

DISCUSSION...

Southeast Michigan will remain along the northern periphery of very strong H5 600 dam ridge that will retrograde from the Southeast U.S. to Texas by Friday. Quick progression of deep northern Canada midlevel trough combined with the expanse of upper level confluence over portions of the Great Lakes will support surface anticyclone here locally and cause the frontal zone and any instability to be suppressed to the south today. Despite the instability to the south, plan view perspective of thermal progs show a fairly significant wave of 850-600mb warm advection directly through Lower Michigan between 06-18z this morning. Will see some upstream convection from Iowa track eastward this morning and at least approach Southeast Michigan. Could see some light precipitation or virga survive the eastward trek but not expecting much in the way of rainfall amounts. Persistent clouds today are expected to have some impact on temperatures which will be in the middle 70s, at or a couple of degrees above normal.

Retrogression of the high and deep column ridging will allow for strong surface ridging over Southeast Michigan Friday. Cooler morning lows with some 40s up north, but right at seasonal averages for low temperatures.

Southeast US monsoonal moisture is forecasted to circumnavigate/ advect around the large Southeast US upper level ridge Friday and Saturday. There has been good model consistency in supporting strong synoptic scale lift from South Dakota Friday eastward into Michigan on Saturday. Strong convergence streamflowing into a region of very strong right entrance region jet dynamics aloft brings high confidence in a storm track within the vicinity. Main concern is the potential for heavy rainfall Saturday. EPS ensemble data highlights an interquartile range of 24 hr QPF of .8 to 1.5 inches with higher values in across the northern cwa including the Tri Cities. PoPs are at 90-95% for the Day 3 period, the daytime on Saturday. The Excessive Rainfall Outlook has much of Southeast Michigan designated as a Slight Risk for Excessive Rainfall Saturday.

For the latter half of the weekend, indications are that an entrance region to the upper level jet streak will stay in vicinity of Southeast Michigan through at least Monday. Easterly flow combined with differential cold advection in the low levels should result in very stable weather with temperatures below normal. Confidence decreases markedly with regards to precipitation potential by Tuesday with hard to determine shortwave energy timing and location.

MARINE...

Winds remain on the lighter side (<20kts) through today as the southern edge of northern Ontario high pressure slides overhead. A secondary cold front drops through the region tonight-Friday with the main impact being a modest uptick in northeasterly winds over the southern half of Lake Huron. This front stalls over northern Ohio before attempting to lift back north Saturday as Plains low pressure arrives. This front looks to only push north of the southern Great Lakes before the system tracks over lower MI resulting in predominant east-southeast turning northeasterly winds this weekend. Widespread showers and scattered thunderstorms are possible, mainly focused over the southern half of the region. A moderate gradient, supporting NE/E gusts 20-30kts, lingers behind the low Sunday into the new work week as the area holds between the stalled boundary over the Ohio Valley and high pressure over northern Ontario.

DTX WATCHES/WARNINGS/ADVISORIES

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