textproduct: Detroit/Pontiac

KEY MESSAGES

- Scattered to numerous showers and thunderstorms this afternoon and evening, with a low risk for severe thunderstorms.

- 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.

DISCUSSION

Clusters of convection continue across srn Mi during the rest of the afternoon into the evening driven by an approaching short wave impulse. Some peaks of sun across portions of the area this afternoon allowed weak destabilization as sfc temps rose well into 70s (south of the stationary front across tri cities/thumb) with sfc dewpoints in the mid to upper 50s. This drove SB CAPE toward 1000- 1200 J/kg. Steep mid level lapse rates across srn Mi combined with fast westerly flow (0-6km bulk shear values of 40 knots) will remain supportive of a low severe weather risk this afternoon/evening, primarily strong winds and large hail. The complexity of storm interaction within multi clusters and likelihood for some rain cooled stabilization will add a layer of uncertainty to overall storm organization/intensity this evening. In fact, the most organized convection upstream has been along the mid level front and elevated above the surface.

An influx of deep layer moisture will drive precipitable water values up to 1 to 1.4 inches by evening. The expected progressive nature of the stronger storms will limit the flooding risk. Shower and thunderstorms will come to an end late in the evening as the short wave departs to the east and the cold front pushes across the rest of the forecast area. Cold but shallow post frontal air will send nighttime temps down into the 30s and 40s. Strong low to mid level anticyclonic flow located over the northern lakes on Wednesday will suppress the frontal forcing south of the state through much of the day. Northeast flow will then result in a relatively cold start to April as highs remain stuck in the 40s (30s across the thumb).

The next upper wave forecast to lift across the western Great Lakes Thursday will drive the low level baroclinic zone back north across the forecast area as a warm front Wed night into Thursday. The corresponding theta e advection will warrant the next chance for rain. Sfc temps near freezing across the northern tri cities region Wed night may support a little freezing rain. Model trends have continued to suggest marginal sfc temps may keep the icing threat limited in duration. The warm sector will lift into most of Se Mi on Thursday, leading to warm and windy conditions. The passage of the associated sfc cold front or pre frontal trough late Thursday will bring the next risk of severe weather. Degree of destabilization will again add uncertainty to the overall severe risk. The medium range model suite show yet another upper wave and associated sfc low tracking across the Great Lakes on Saturday, with Se Mi likely in the pre frontal warm sector.

MARINE

Post frontal north winds will last through the night as strong high pressure expands across the northern Great Lakes. An upper short wave and elevated instability will support rounds of showers and thunderstorms this evening before more stable air advances across the region overnight. The northeasterly gradient will increase Wednesday into Wednesday night as the surface high depart to the east and a warm front approaches from the south. Low pressure is then forecast to track from the western Great Lakes into the northern Great Lakes Thurs into Thurs night. Easterly gale force winds carry a low probability across the north half of Lake Huron Thursday as this low approaches.

HYDROLOGY

An influx of deep layer moisture will drive precipitable water values up to 1 to 1.4 inches by evening. The expected progressive nature of the stronger storms will limit the flooding risk. Some regenerative convective elements within the multi cell clusters may however result in some localized rainfall amounts over an inch. There are additional chances for rain Wednesday night and Thursday. Current probabilistic guidance limits the risk for excessive rainfall with this next system.

PREV DISCUSSION

Issued at 1220 PM EDT Tue Mar 31 2026

AVIATION...

The primary aviation concern this afternoon and evening is the development of multiple rounds of convection associated with a strong southward-sagging cold front.

Afternoon/Early Evening: Sustained southwest flow remains breezy with gusts frequently reaching 30 kt ahead of the front across the southern TAFs. VFR conditions currently prevail, but a rapid transition to MVFR/IFR is expected as a line of strong to potentially severe thunderstorms develops between 19z and 23z. High probability of TSRA impacting all terminals, with the potential for localized gusts in excess of 45 kt, hail, frequent lightning, and brief visibility reductions to 2SM or less.

Frontal Passage (FROPA): The cold front is expected to clear FNT/PTK between 00-02z and the Detroit terminals (DTW/YIP/DET) around 03z.

Post-Frontal: Following the frontal passage, winds will shift abruptly to the north and then north-northeast overnight. While there is significant drying and subsidence aloft, enough low-level moisture looks to remain trapped to sustain an MVFR deck (015-025) through the overnight hours. With low-level winds coming off Lake Huron, have opted to hold MVFR ceilings into Wednesday afternoon, though confidence decreases toward the end of the period.

For DTW... Thunderstorm probability remains high late this afternoon. Current timing suggests a primary window for convection between 19z and 00z. Winds will remain southwesterly (220-240) until a late-evening shift to the north. MVFR ceilings are expected to hold overnight following the rain.

DTW THRESHOLD PROBABILITIES...

* High for ceilings at or below 5,000 ft after 20z and through the evening hours, then medium.

* High for thunderstorms late this afternoon and early evening.

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.