textproduct: Detroit/Pontiac

KEY MESSAGES

- Scattered to numerous showers and thunderstorms redevelop over all of SE Mi this afternoon. Scattered severe thunderstorms are possible with damaging wind the primary hazard but also including potential for large hail and tornadoes.

- A strong cold front fuels storms but also a chance for excessive rainfall. There is a Marginal to Slight Risk of excessive rainfall mainly along and south of M-46 this afternoon and evening.

- After the front tonight, temperatures drop back to normal or slightly below normal for Wednesday and Wednesday night. A brief period of wintry mixed precipitation is likely north of M-46 Wednesday night until become all rain by sunrise Thursday.

- Another low pressure system brings rain and a chance of thunderstorms Thursday and Thursday night.

AVIATION

Breezy SW wind continues to feed mild air into Lower Mi and into the frontal zone/outflow located from FNT northward at forecast issuance this morning. VFR warm sector conditions are in place south of the frontal zone across the DTW corridor with only borderline MVFR along and north of the front, mainly tied to residual fog after earlier thunderstorms. The outflow then washes out as the front moves northward with low pressure consolidating in northern Lower Mi by this afternoon. VFR warm sector conditions hold across the terminal corridor until the next round of showers and thunderstorms develop during the afternoon with numerous coverage through this evening as cold front advances across the area. Areas of MVFR ceiling and IFR visibility in showers and storms become widespread MVFR ceiling with wind shifting north behind the front tonight into Wednesday morning. For DTW... The probability for thunderstorms increases this afternoon and evening, with one or more rounds of storms likely during this time.

DTW THRESHOLD PROBABILITIES...

* Low for ceiling 5000 ft or less this morning, then medium this afternoon, and high tonight. * Moderate to high for thunderstorms this afternoon and evening.

PREV DISCUSSION

Issued at 405 AM EDT Tue Mar 31 2026

DISCUSSION...

The overall northward shifting trend of late night convection heading into sunrise leads to a morning pause and shifts the forecast focus to severe storm potential this afternoon and evening. Low pressure consolidating in northern Lower Mi draws the warm front northward and solidifies the warm sector across SE Mi for the cold front to sweep through late today and this evening. Consensus of hi- res and regional models among the 00Z runs suggest two phases in the convective pattern this afternoon. The first is tied to activation of the warm sector theta-e ridge early in the afternoon that is forced by very broad mid level height falls and improved positioning of the upper jet. This occurs as HREF mean surface based CAPE fails to reach 1000 J/kg across SE Mi, partially due to cloud deprived surface heating and partially due to early convective initiation. Morning cloud trends will be key to monitor for potential CAPE overachievement, as much as possible given the low CAPE density profiles in model soundings. Otherwise, the wind and shear profiles still look very favorable for storm organization with just enough low level curvature to produce rotation in discrete storms that evolve into linear modes later in the day.

The early afternoon phase of storms complicates expectations for convective mode along the cold front by late afternoon and this evening, mainly in terms of how much if any instability remains after early day initiation. What is not in doubt is moisture availability and sufficient forcing along the front that combine to maintain a heavy rain threat as the front moves slowly but steadily north to south across southern Lower Mi. The Day 1 ERO covers SE Mi generally along and south of the I-69 corridor where HREF mean QPF places greater potential for rainfall totals in the 1-2 inch range before the front settles south of the Ohio border after midnight.

A few rain showers linger near the Ohio border during Wednesday while the weather highlight becomes colder air inbound from James Bay high pressure. Brisk northerly wind carries temperatures down into the mid and upper 30s most areas by Wednesday morning, and to around the freezing mark toward the Lake Huron shoreline. Daytime recovery into the lower 40s inland from the Lake is about all that can be managed during the day. This temperature distribution then leads into potential for a wintry mix of precipitation, mainly north of M-46, as the next low pressure system approaches and interacts with the Ohio valley front. Blended guidance maintains a rain/snow/freezing rain mix but has backed off snow accumulation and pushed light icing farther north toward US-10 before changing everything over to all rain by sunrise Thursday.

MARINE...

A frontal boundary draped across central lower Mi will remain the focus for shower and thunderstorm activity during the early part of the day. A surface low tracking across the region will draw a cold front across lower Michigan and adjacent marine waters in its wake during the afternoon and evening hours. A line of strong to severe thunderstorms will be possible along the frontal passage during this time, in which localized gusts in excess of 35 knots will be possible. Elevated winds and/or waves will be driven mainly by thunderstorm activity, as otherwise stable conditions prevent gusts from mixing to the surface. A cooler post-frontal airmass then moves in tonight and Wednesday as flow shifts to the north-northeast with the frontal passage. A period of onshore flow will bring elevated wave activity into the nearshore waters during this time. Northeast to easterly wind will strengthen Wednesday night and Thursday as widespread precipitation expands across the area ahead of a low pressure system. Potential for thunderstorms will increase again late Thursday and Thursday night as the low tracks across the area.

HYDROLOGY...

An active period of showers and thunderstorms continues today and this evening across SE Michigan with locally heavy rainfall likely, mainly south of I-69 across metro Detroit to the Ohio border. Model probabilities remain high for total rainfall of 1/2 inch to 1 inch across the region before ending tonight. There is however lower probabilities for localized rainfall of 2 to 4 inches in areas of more persistent thunderstorms. This threat area is farther south toward metro Detroit and the Ohio border as the associated cold front moves slowly across the area late this afternoon and this evening. Localized flooding is possible, especially in more urbanized areas. The slow moving frontal boundary will linger across the metro Detroit and Ann Arbor areas late tonight into Wednesday, supporting additional chances for light rain. The rainfall pattern remains active during the late week period as a series of fronts and low pressure systems move across Lower Michigan, although with additional totals generally less than 1 inch.

DTX WATCHES/WARNINGS/ADVISORIES

MI...None.

Lake Huron...Small Craft Advisory from midnight tonight to 8 PM EDT Thursday for LHZ421-441.

Small Craft Advisory from 8 AM Wednesday to 8 PM EDT Thursday for LHZ422.

Small Craft Advisory from 4 AM Wednesday to 8 PM EDT Thursday for LHZ442-443.

Lake St Clair...None.

Michigan waters of Lake Erie...None.