Marine Weather and Tide Forecast for Gibraltar, MI

DISCUSSION

Differential 1000-500mb geopotential height rises are now occurring over the central Great Lakes as the composite trough is moving out into the Atlantic. Significant warm advection episode has begun with 850mb temperatures rising some 5 degrees C between 06-12z this morning. First item this morning is a minor, saturated, upright frontal structure on the 298-308Ks surfaces that will work across the northern cwa. Virga will likely show up on radar this morning, but it is difficult to envision much in the way of QPE with forecast soundings showing saturation limited to a highly stable layer between 2.0 and 6.0 kft agl. Notable moderation of surface temperatures with afternoon readings in the upper 60s to around 70 degrees which will likely be some 20 to 25 degrees warmer than yesterday. Final item for the afternoon will be reservoir of elevated instability, MUCAPE of 250-500 J/kg, that will expand eastward into southern portions of Southeast Michigan. Subtle shortwave anchored on the entrance region of midlevel jetlet feature is forecasted to track directly across Southeast Michigan between 19- 01z. Quite the tenuous forecast as direct cva appears to be enough forcing for lift despite what really looks like residual stability between 5.0 and 10.0 kft agl. Thus, there really are questions about the coverage and location of activity this afternoon with a subset of hires CAM data that has trended more bullish with afternoon/evening activity. Per model trends, expanded the chance PoPs northward to include much more of the cwa. Gusty winds will be possible with lower column evaporation allowing for some downward momentum fluxing. Not expecting any strong or severe weather because of low instability and a timing that appears to be just out of phase with greatest surface based lapse rates. There does appear to be a surface inversion particularly for eastern portions of the forecast area.

Cold advection trailing the wave of weak low pressure will push a surface cold front to the south of the forecast area tonight.
Moderation will still allow many areas to climb into the upper 60s to lower 70s Wednesday, however north surface winds will keep conditions chilly for the Thumb and areas downwind of the Lake Huron. The overwhelming bulk of model guidance is dry for Wednesday but the GEM and the hires Canadian guidance is suggesting convection will be possible Wednesday evening over Monroe and Lenawee counties.
The solutions with precipitation suggest lake breeze forcing will be possible. Given the lack of development in the other guidance will continue to go dry. Expecting a dry air mass with very high CIN in the 3.0 to 10.0 kft agl layer.

High predictability exists for warm conditions Thursday and Friday with high amplitude ridge expanding across all of eastern North America. High temperatures Thursday and Friday are expected to be well into the 70s for locations not in close proximity to Lake Huron. High solution variance continues regarding next weekend, therefore very low confidence in timing and duration of precipitation Saturday and Sunday. The latest ECMWF is back to suggesting a closed low or cutoff low remaining back across the northern Plains for at least the first half of the weekend. Latest timing suggests an occluded front pushing through the area early Saturday. Very low confidence in the weekend forecast.

MARINE

Gusty south wind persists across the region today ahead of a weak disturbance set to work through this evening into tonight. Small Craft Advisories remain in effect for the Lake Huron nearshore waters where gusts of 25+ kt and wave heights of 4+ feet are forecast through early afternoon before gustiness subsides. Showers and thunderstorms are possible tonight, mainly across Lake St. Clair and western Lake Erie, as the disturbance passes through. Severe weather is not likely. Lighter wind follows on Wednesday as weak high pressure settles in. The next low begins to take shape over the upper Midwest midweek, eventually sending a warm front into the Great Lakes late Thursday into Friday. This brings moderate southeast flow and the next chance for showers and storms.

PREV DISCUSSION
Issued at 1207 AM EDT Tue Apr 21 2026

AVIATION...

VFR skies will prevail through the early morning hours with limited coverage of high clouds and light winds. There will be an increasing coverage of mid clouds along with a low chance for very light rain showers mid-morning as next wave moves into the Great Lakes with a sagging frontal boundary. Chance of occurring remains too low to mention in TAFs at this time. Mid clouds hang around during the day as southwesterly winds increase ahead of the approaching weak front.
Gusts to around 25 knots will be possible. Increased ascent along the frontal zone offers a better chance at showers and possible thunderstorms late this afternoon and evening across the southern metro terminals.

DTW THRESHOLD PROBABILITIES...

* Low for thunderstorms between 2100Z today and 0600Z Wednesday.



DTX WATCHES/WARNINGS/ADVISORIES
MI...None.
Lake Huron...Small Craft Advisory until 2 PM EDT this afternoon for LHZ421-422- 441>443.

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