Marine Weather and Tide Forecast for Grosse Pointe, MI

AVIATION

High pressure influence wanes tonight as a low pressure system lifts northeast across the Upper Midwest. Elevated portion of the system's warm front is already making inroads across southern Lower Michigan per warming of the 1-3 km AGL layer, based on ACARS soundings. This promotes column moistening amidst the shift to southerly low-level flow. Expect current precipitation arc to hold over central Lower through the next 6-8 hours given closer proximity to the upper-level wave and stronger vapor transport processes. Still, cannot rule out some virga early tonight, especially over mbS. Models suggest sufficient moistening should be achieved shortly after 06Z with a line of showers lifting in from the southwest. Lapse-rates aloft aren't particularly impressive, but a few showers could generate occasional lightning as a plume of weak elevated instability also moves in. Ceilings are expected to drop into MVFR category with lingering morning showers as surface winds lag, eventually veering south-southwesterly. Mixed-layer activates late Monday morning with the initial cold front which leads to strong gusty winds during the day and winds veering toward the west. Potential exists for some additional shower activity and gusts in excess of 30 knots.

For DTW...Cannot rule out a thunderstorm or two early Monday morning, then showers linger through the rest of the morning hours.
Wind gusts spike during the afternoon.

DTW THRESHOLD PROBABILITIES

* Low for ceiling at or below 5000 feet early tonight, then medium Monday morning.

* Low for thunderstorms early Monday morning.

PREV DISCUSSION
Issued at 338 PM EDT Sun Apr 20 2025

DISCUSSION...

Upper-level confluent flow through the morning has reinforced high pressure this afternoon with a 1032mb pressure center now located over the Georgian Bay. This has and will continue to support dry weather with mostly sunny conditions, which have allowed temperatures to cap out in the low to mid-50s despite the lingering thermal trough. A compact upper-level wave has helped organize a weak low pressure system over the Panhandle of Texas which will then pivot and track into the Central Plains and Midwest, just west of Lake Michigan. Upper-level trough will turn negatively tilted owing to the maturing system with the low pressure system becoming a little more organized, reaching an occluded state as it traverses into the Great Lakes tomorrow.

Impacts for SE MI will initially be the boost in theta-e advection which will mitigate the full range of nocturnal cooling overnight, with lows holding in the mid 40s. A warm front will initiate rain chances throughout the morning hours with some additional support aloft along the nose of an upper-level jet. While not conforming to the traditional jet streak model, rossby number analysis highlights a boost in ageostrophic circulation through the right exit region.
Cannot rule out some isolated thunderstorm production given modest elevated instability with mid-level lapse rates aoa 6 C/km. Passage of the low into the northern Great Lakes tomorrow will sweep a cold front over the state in the late morning and afternoon hours.
Pending the timing of the front, some modest surface based cape may intersect the frontal passage, bringing a window for isolated thunderstorms leading into the afternoon before a dry slot works in.
Steeper lllr during daylight hours and will the passage of the cold front will aid in shallow mixing which will be enough to tap into stronger winds aloft up to 45 knots. Accounting for momentum transfer, wind gusts around 40 mph will be likely through the day, with some isolated gusts to or just above 45 mph possible. Lack of foliage on trees limits concerns for isl/sct power outages.

Precipitation chances will remain on the lower side through the midweek period due to the lower predictability under zonal flow aloft. Ensembles are highlighting the possibility for additional chances on Wednesday along an stationary frontal slope, but this will be pending the final location of the front and degree of overrunning, which at this time looks weak. Of higher confidence, normal to above normal temperatures are likely through the mid to late week period again due to a more stagnant upper-air pattern.

MARINE...

1034 mb surface high pressure migrates further into Quebec this evening, leaving in its wake light easterly flow across all local waters. Low pressure now over the southern Plains will lift along an existing frontal zone to the Straits by Monday evening, drawing an occluded front through the region Monday afternoon. Ahead of this front, strong moisture advection occurs in the midst of a 50 knot low level jet which also elevates winds/waves to at least Small Craft Advisory thresholds. Widespread showers and embedded rumbles of thunder will be possible late tonight-Monday morning as a result.
Stability in the warm frontal zone of this system should keep gusts aob 30 knots through Monday afternoon, but once the front comes through and the boundary layer mixes, there is potential for gusts to increase Monday evening/overnight. Momentum transfer fields flirt with 35-40 knots for both Saginaw Bay (Monday evening) and northern Lake Huron (late Monday night), where veering wind profiles briefly align with their respective major axes. That said, lack of model consensus and short duration/marginal magnitude of this setup do not afford the confidence to go with a Gale Warning with this issuance.
Will continue to monitor forecast trends. Otherwise, conditions improve on Tuesday as high pressure returns to the Great Lakes.

DTX WATCHES/WARNINGS/ADVISORIES
MI...None.
Lake Huron...Small Craft Advisory from 8 AM Monday to 10 AM EDT Tuesday for LHZ421-422.

Small Craft Advisory from 4 AM Monday to 10 AM EDT Tuesday for LHZ441>443.

Lake St Clair...Small Craft Advisory from 10 AM Monday to 4 AM EDT Tuesday for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory from 10 AM Monday to 4 AM EDT Tuesday for LEZ444.