textproduct: Detroit/Pontiac

KEY MESSAGES

- Below normal temperatures Sunday through early next week.

DTW THRESHOLD PROBABILITIES

* High for ceiling at or below 5000 ft through Sunday afternoon. Low Sunday evening.

* Moderate for ptype to be rain/snow mix Sunday early afternoon.

PREV DISCUSSION

Issued at 339 PM EDT Sat Apr 4 2026

DISCUSSION...

A couple of near-term items to note, including the issuance of the Severe Thunderstorm Watch and the Flood Watch. For the Severe Watch... still looking at a small geographic footprint for severe weather as the northern edge of a line of storms reaches extreme southeastern Michigan. Surface instability is still not convincing compared to counties just a row south, but the main concern is how the inbound cells will interact with the boundary layer and the strength of the cold pool that has developed. Storm mode and slight bowing look to the incoming cell lends to a damaging wind threat if these storms are still surface based. Highly convergent, backed flow at the cusp of the marine layer is also a concern for a brief spin up tornado, which is being monitored closely. There has been brief rotation observed with these cells. The severe weather threat is mainly confined to Monroe County with storms elsewhere remaining elevated (confirmed by backed wind profiles and temperatures still in the 50s). The severe threat ends as this line moves into Ontario, likely by 5pm. Flood Watch issuance will be discussed in the Hydrology section.

Post-frontal cold advection drops h8 temperatures into the negative single digits tonight, allowing lows to fall into the mid to upper 30s Sunday morning. Multiple shortwave perturbations carve through the mean flow to reinforce longwave troughing across eastern CONUS through mid-week, leading to a stretch of below normal temperatures across the Great Lakes. One such perturbation glances across the area mid-day Sunday, engaging remnant boundary layer moisture and instability to generate scattered showers, possibly mixed with melting snowflakes as highs only reach the low to mid 40s. Breezy west winds (gusts of 30-35 mph) are also expected tonight-Sunday as the parent low peels away, only gradually drawing its gradient wind field with it.

Unsettled weather persists into the early week period as broad troughing holds steady overhead. This sends a series of progressive shortwaves into the Great Lakes between late Sunday night and Tuesday morning. There is a glancing shot for a rain-snow mix early Monday morning as the first of these waves arrives, although with minimal impacts as morning lows only briefly touch freezing. Better opportunity for snowflakes to mix in exists with a second wave Monday night, but this time with strong cold advection surging in behind it. Could even see a dusting of accumulation over the Thumb while temperatures plummet into the low 20s across the state by Tuesday morning. Both of these waves have only modest forcing/moisture prospects, but steep mid level lapse rates (nearly 7.0 C/km) could briefly enhance rates at times or result in ice pellets/graupel development.

High pressure then returns for Tuesday into the mid-week period while return flow re-establishes the gulf connection for the latter half of the week.

MARINE...

Broad low pressure passes northeast across the central Great Lakes this evening. Widespread showers will continue with embedded thunderstorms focused mainly across western Lake Erie, Lake St. Clair, and southern Lake Huron. Isolated storms may be strong to severe through this evening. Southeast wind veers around to southwest tonight, increasing to 15 to 20 kt with gusts to 25 kt as cold advection ensues. Wind direction continues veering to westerly on Sunday, with an uptick in magnitude expected. A Gale Watch has been issued for northern Lake Huron with gusts to 35 kt increasingly likely there. Elsewhere, gusts of 20 to 30 kt will be more likely before wind diminishes and veers to northwest Sunday night. Small Craft Advisories are in effect for the Lake Huron nearshore waters through this period. A clipper system passes through on Monday with an uptick in northwest winds expected Monday night in its wake. Cooler northwest flow persists into Tuesday.

HYDROLOGY...

Rainfall this morning led to widespread rain totals of 1 to 3 inches, with additional rain moving in this afternoon and early evening. Reports of areal flooding and rises on area rivers will be exacerbated by this additional rainfall, which may exceed one inch in some locations especially in any thunderstorms. A Flood Watch has been issued to account for the worsening of ongoing flooding issues with this next round of rain. Several River Flood Warnings are in effect at issuance. The heavy rainfall threat ends this evening with drier conditions forecast Sunday through middle of next week.

DTX WATCHES/WARNINGS/ADVISORIES

MI...Flood Watch until midnight EDT tonight for MIZ047-048-053>055- 060>063-068>070-075-076.

Lake Huron...Gale Warning from 6 AM to 8 PM EDT Sunday for LHZ361-362.

Small Craft Advisory until 10 PM EDT Sunday for LHZ421-422-441>443.

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