Marine Weather and Tide Forecast for Grand Beach, MI

UPDATE
Issued at 1012 PM EDT Mon Jul 27 2026

The severe threat has greatly diminished in the wake of the afternoon and early evening storms, especially southwest of a Benton Harbor to Jay county line. NE of this area loss of daytime heating has reduced the overall instability as well.
That being said, a weak disturbance was causing widely scattered showers and storms from NW of Chicago to South Haven with somewhat of an increase for points to the NE. The storm by South Haven is on the stronger side, but not likely to produce much more than some gusty winds and maybe small hail. Some CAMs suggest an uptick in shower/storm coverage over the next several hours mainly for NE parts of the forecast area. Confidence is on the lower side for this to occur, but given the upstream convection is holding its own and the LLJ will ramp up somewhat at least scattered convection seems plausible. Have cleaned up pops quite a bit and tended to limit chc pops to the NE areas into the overnight hours.



DISCUSSION
Issued at 255 PM EDT Mon Jul 27 2026

The main forecast concern will be on the severe weather potential through this evening.

A complicated convective scenario is unfolding across the Great Lakes region this afternoon. Preferred region of convective development has been across northeast Illinois along a corridor of low level warm/moist advection. This forcing is coincident with strengthening upper low level flow and effective shear profiles. Extreme instability with MLCAPES 4-5k J/kg CAPES is situated across northeast Indiana with sharp eastward diminishment in instability across northeast Indiana/northwest Ohio. Cells across northeast Illinois are favoring strong cold pools with signatures of very strong base velocity shifting southeast across far northwest Indiana. The combination of shallow low level southwest flow and deeper northwesterly flow in the mid/upper levels is favor some north to south preference in propagation vectors with the storms across northeast Illinois. Areas west of US Route 31 across northeast Indiana should stand greatest risk of seeing higher end thunderstorm wind gusts (80+ mph) as the storms across NE Illinois drop southeast. In addition to the risk of higher end damaging wind gusts, the extreme instability will support some isolated large hail of 1 to 2 inches in diameter. Also, the aforementioned background shear profiles will continue to support some embedded supercell structures with a risk of isolated tornadoes. 0-3km shear vectors oriented from the northwest at around 30 knots could also support a few QLCS tornado spinups where any rear inflow jet can orient in a NW to SE fashion and where more mature cold pools develop.

Additional storms are expected to develop across the Great Lakes region this evening as low level front pushes southward with an additional risk of scattered damaging wind gusts through around 02Z.
Confidence in severe gusts after 00Z does diminish somewhat however.

By Tuesday morning, the nose of the upper level jet streak will reach the Mid Atlantic states with lagging sfc trough/cool front expected to extend from western PA to southern Illinois. Passage of this front will lead quieter weather conditions through the middle of the week with temperatures/dew points closer to seasonable levels.

The next system to watch will be toward end of the work as the potential exists for synoptic wave to become convectively enhanced across the Dakotas. Some question exists as to instability magnitudes as far east as southern Great Lakes/Ohio Valley with this system with some indications of this system becoming more vertically stacked in nature well to the west.

AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/
Issued at 735 PM EDT Mon Jul 27 2026

The potential of thunderstorms has diminished across the terminals this evening. Some lingering light rain should clear the terminal by 00Z. Cannot completely rule out isolated showers late this evening/early overnight as cold front approaches from the north, but this probability appears too low to include with the 00Z TAFs. Some post-frontal stratus and perhaps some fog could develop late tonight into early Tuesday morning, with greater confidence in stratus development opposed to fog.
IFR/MVFR cigs should gradually mix out late tomorrow morning into early afternoon with northwest winds becoming gusty to 15 to 20 knots.

IWX WATCHES/WARNINGS/ADVISORIES
IN...Beach Hazards Statement through Wednesday morning for INZ103.
OH...None.
MI...Beach Hazards Statement through Wednesday morning for MIZ177- 277.
MARINE...Small Craft Advisory from 2 AM Tuesday to 2 AM EDT Wednesday for LMZ043-046.