Marine Weather and Tide Forecast for Pinckney, MI

AVIATION

Squall line producing very strong winds, large hail, isolated tornados, and persist downpours continues to work from west to east across the terminals tonight. Gusts in excess of 60 knots and at least one confirmed tornado have been reported upstream with this system. Trends continue to favor MVFR visibility reductions in the main rain band, with brief IFR reductions noted at mbS and FNT.
Timing the exit is the main forecast concern for the next TAF cycle as the lingering back-edge will be slower to depart from DTW and DET near the very beginning of the TAF window. The line should fully clear east of all sites by 07Z. Post-frontal VFR conditions move in early Friday and throughout the day. Surface flow weakens, backing from southwest to southeast during the afternoon. Additional showers and storms possible late Friday evening.

For DTW/D21 Convection... A decaying line of strong to severe thunderstorms crosses DTW during the 05-06Z time window.

THRESHOLD PROBABILITIES...

* Medium for ceiling 5000 feet or less toward midnight through sunrise the low through Friday.

* High for thunderstorms tonight, mainly 05-06Z Friday, then low confidence after 00Z Saturday.

PREV DISCUSSION
Issued at 307 PM EDT Thu May 15 2025

DISCUSSION...

Moderate instability has built up across southeast Michigan with MLcapes aoa 1500 J/kg with sbcapes 2000-3000 J/kg as of 18z. None- the-less, just a modest CU field around as warm/dry mid levels cap activity for now. Severe thunderstorm chances will begin to increase this evening with arrival of the height falls and increasing wind fields, but bulk of thunderstorm activity looks to be impacting southeast Michigan around midnight. With the southeast winds, a stabilizing marine influence off of Lake Erie/Lake St. Clair looks to be coming into play, but an enhanced low level temperature/instability gradient will set up across the western half of the CWA (along/west of US-23). These locations stand the best chance of activity remaining surface based, and thus the greatest potential for damaging wind gusts with a chance of tornadoes as 0-1 KM bulk shear resides in the 25 to 30 knot range. With increasing southwest low level jet (50+ knots) and steep mid level lapses, large hail will be a concern as well, as cape (1500+ J/kg) is maximized around the freezing level to -20 C. Progressive nature of activity will limit flood threat, but urban areas (Wayne county) are not completely out of the woods, as strong to severe thunderstorms could drop a quick 1.5-2 inches in an hour in localized spots, as PW values peak around 1.75 inches. Majority of hi-res solutions all generally indicating a broken to near solid line of showers/thunderstorms rolling through, ending 2-4 AM.

With the large 500 mb low center still back across the Western Great Lakes on Friday, deep southwest flow will promote another warm day, as 850 mb temps around 15 C will be supportive of high temperatures in the low to mid 80s. A spoke of energy/shortwave looks to be rotating around and tracking through southeast Michigan around midnight once again. Confidence is high in another round of showers and thunderstorms developing late Friday evening/night as the healthy cold front tracks through. Although instability parameters are less than this evening, wind fields/bulk shear and capes in 1000-2000 J/kg range seem supportive of at least a marginal risk of severe storms.

Cooler and breezy on Saturday, as surface low (992-994 mb) tracks through the northern Great Lakes. Pretty good cold advection with 850 mb temps lowering into the mid single numbers. Steepening low level lapse rates during the day generates some modest cape, which may touch of isolated-scattered showers. Otherwise, local probabilistic guidance suggests wind gusts of 30-40 MPH during the day.

Weak shortwave riding for Sunday, but there is already another shortwave/re-enforcing shot of cold air to track through the Great Lakes region for Sunday night. Dry air and northwest confluent flow looks to keep us dry to start the work week. Another large low pressure system to develop over the Central Plains, but still uncertainty with the magnitude and areal extent during the mid week period, which will impact the timing of showers returning to southeast Michigan.

MARINE...

Light E/SE flow continues across the region this afternoon-evening though funneling down the Saginaw Bay has allowed for local enhancement towards 15kts. A warm front tied to strong northern Plains low pressure is currently lifting out of the Ohio Valley towards the Great Lakes this afternoon. A line of strong/severe thunderstorms is expected to develop over the western Great Lakes and push through our area late evening-early tonight (~10p-3a). All hazards (strong winds, hail, waterspouts) are in play though wind gusts greater than 40kts and hail above a half inch are the main threats. Southerly winds up to 15-20kts develop post front for Friday as the low tracks over Lake Superior. This system then sweeps a cold front through the central Great Lakes late Friday evening- early Saturday night generating another line of showers and thunderstorms- a few of which could be severe (wind and hail hazards). Moderate west-southwest winds follow Saturday with the strongest winds (20-30kts) expected over the southern half of the region where the gradient is strongest. Small craft advisories are likely needed for most if not all nearshore waters as a result. Low fully departs Sunday shifting winds to the northwest. Gusts peak near 20kts during the day before weakening overnight as weak high pressure slides overhead.

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