Marine Weather and Tide Forecast for Grosse Pointe, MI

AVIATION

A stalled frontal boundary near the I-69 corridor remains a focus for convective initiation and additional storms early this afternoon. Meanwhile, a disturbance is driving a cluster of storms across the Metro area that will depart over the next hour or two. A humid air mass holds in place with enough instability recovery expected to support a round of organized/linear convection later this afternoon into the evening as a strong low lifts in from the Mississippi Valley. This round is highlighted in the prevailing +TSRA group. Some of these storms may be severe with gusts up to 50- 60 kt as well as torrential downpours dropping vsby to IFR or briefly LIFR. Ceilings lower to MVFR/IFR as the low tracks through the area tonight through Thursday morning, and showers are likely to linger overnight as well. Slightly less humid northwest flow follows through early Thursday with ceilings trending back toward VFR during the afternoon.

For DTW/D21 Convection...Ongoing convection exits shortly with a relative lull in activity this afternoon before a broken line of showers arrives from the southwest between 22 and 23z. This will be capable of severe weather as well as torrential rainfall. This is followed by a dry slot with gusty southwest wind overnight.

THRESHOLD PROBABILITIES...

* High for thunderstorms between 22 and 02z this afternoon and evening.

* Moderate for ceiling aob 5000 ft this afternoon, then high tonight.

PREV DISCUSSION
Issued at 958 AM EDT Wed Jun 18 2025

UPDATE...

Severe storm potential remains the weather highlight across SE Mi with a few twists and turns already to consider this morning for the forecast this afternoon and this evening. The morning flare-up of elevated convection across the Tri Cities and northern Thumb gained enough coverage and intensity to fortify the surface front near the I-69 corridor. Satellite trends suggest residual cloud cover will maintain the gradient there while temperature increases across the warm sector to the south. New development of surface based storms is possible along this frontal zone early to mid afternoon. Strong surface heating south of the front also gives the ongoing northern Indiana cluster of storms a chance to become more surface based during late morning to early afternoon with potential for increasing impacts into SE Mi. All of these developments still leave ample time for recovery of instability ahead of the primary MCV-driven event that is on schedule for this evening. Mid morning observations toward southern IL/northern MO show impressive MCV intensity poised to interact with the larger scale warm sector having RAP CAPE projections of 3000+ J/kg by 18Z. A strongly forced convective system is expected to result which is timed into southern Lower Mi toward 00Z this evening.

PREV DISCUSSION...
Issued at 335 AM EDT Wed Jun 18 2025

DISCUSSION...

For this morning... Isolated to widely scattered showers and thunderstorms will be possible either from the activity upstream over Lake Michigan and/or off a frontal boundary that resides north of I-69. Surface instability has waned through the overnight hours, but ambient conditions within this humid airmass sustain elevated instability with mid-level lapse rates aoa 6 C/km, bringing continued chances for elevated convection.

SBCAPE rapidly rises through the daylight hours where there will be multiple possible mechanisms for CI. Development along the aforementioned front (which is projected to stall out generally north of I-69) or upscale growth from upstream renewed development sourcing from residual outflows or convergence along the land/lake interface over Lake Michigan look to be the main mechanisms for any early development. Free convection within the warm sector is also a possible under this unstable airmass. As such, scattered to numerous development will be likely and with CAPE building to 1,000-1,500 J/kg and 1-6 km shear ranging between 20-30 knots (stronger closer to the front), organized updrafts will be supported. This brings the chance for strong to severe thunderstorm development as early as this afternoon, with initial threats favoring damaging wind gusts from wet microbursts potential. A tornado cannot be ruled out given any streamwise enhancement with the frontal boundary, and storm relative hodographs do show streamwise vorticity through 3km, but the magnitude of the shear is modest at best.

Severe weather coverage and threat potential will increase through the evening hours with attention turning to a low pressure system and convectively enhanced potent shortwave with a fast translation speed that is projected to pivot right across Michigan in the later afternoon and evening hours. There will likely be ongoing activity across Illinois and Indiana that will pivot into the cwa where strong thermodynamic and kinematics enhance the severe weather threat. A strong low-level jet will nose into SE MI just downstream of the wave with flow subtly backing aloft, greatly elongating the 1- 3 km shear vectors. An MCS/MCV with some embedded quasi-linear structures will be likely where severe threats then pivot to damaging wind gusts of 60-70+ mph, owing to any bowing segments within the line. Embedded mesovorticies leading to tornadogenesis, particularly where any bowing further enhances the streamwise vorticity which is already favorable, is also possible.
Additionally, the front will again act as another spot for tornadogenesis where backed surface winds along the boundary lead to local enhancements to 0-1km SRH and streamwise vorticity ingestion.
Hail to an inch will be a secondary hazard with convection today, but is less favorable due to the warm and humid conditions but cannot be ruled out given any vigorous updraft or meso production.

Last, all thunderstorms will be capable of producing heavy downpours leading to localized flooding concerns. Deformation northwest of the low brings higher potential for prolonged rainfall totals. Please see the hydrology section for additional flooding information.

The severe thunderstorm threat will end late tonight as the system exits and instability wanes, but lingering precipitation will be likely through the morning hours with the continued advection of wrap around moisture. A shortwave trough pivots over Michigan tomorrow afternoon, bringing renewed chances for showers and thunderstorms with modest deep layer shear around 20 knots with CAPE values building towards 1000 J/kg. Overall lack of forcing may inhibit coverage potential. Saturday has the potential to be mainly dry, pending the track of a shortwave with is expected to path over northern Michigan at this time. The main story for next week will be the ridge of high pressure that sets up across the eastern US and Great Lakes which advects and hold 850mb temperatures up to 22C across the state. This will be an extremely high confidence setup to see well above normal temperatures that will challenge if not exceed the 90 degree mark for several days this weekend into early next week, pending storm chances. Heat indices may challenge 100F with dew points in the upper 60s to low 70s.

MARINE...

A strong low lifts into the region today providing several rounds of thunderstorms. Some of these storms could necessitate Special Marine Warnings for locally higher winds and waves, in addition to an isolated large hail and waterspout threat. Non-thunderstom gusts should largely hold below Small Craft Advisory criteria amidst veering ESE flow. Active pattern continues through the end of the week as the system's cold front stalls across the region Thursday.
Gradient winds strengthen, especially over Lake Huron, in the wake of the low with northwest flow up to 20 knots. Another weak low is expected heading into the weekend offering more showers and storms.

HYDROLOGY...

Gulf moisture feed pushes PW values near daily records (at or above 1.75") and offers heavy rain/flooding potential with storms today.
With this very warm/humid airmass, forecast soundings show warm cloud depths of 12-15kft throughout the day increasing precip efficiency with both any preceding showers/storms along the warm front daytime today as well as convection with the low itself late day.

Model guidance continues to show some support for training convection during the day along the warm frontal boundary before the arrival of the low which could boost overall QPF. Average rainfall totals over the course of Wednesday will be 0.75-1.50 inches with locally higher totals (1.5-3+") likely.

The Tri-Cities to northern Thumb will be most likely to see a larger areal footprint of these higher end totals given both the aforementioned thunderstorm training, but also noting any deformation with the low pressure system and longer lasting rainfall potential into the early morning hours. Being said, all strong thunderstorms have the potential to rapidly produce a quick 1-2" of accumulation in a short window, leading to localized flooding potential for all locations across SE MI.

DTX WATCHES/WARNINGS/ADVISORIES
MI...None.
Lake Huron...None.
Lake St Clair...None.
Michigan waters of Lake Erie...None.