textproduct: Grand Rapids

KEY MESSAGES

- Heavy rain possible Monday night into Tuesday

- Thunderstorms, some severe, likely Thursday/Thursday night

- Possibly dry Friday, then a chance of storms this weekend

DISCUSSION

Issued at 203 PM EDT Sun Jun 7 2026

- Heavy rain possible Monday night into Tuesday

The prospects for locally heavy rain beginning Monday night continue to grow. Forecast soundings advertise precipitable water (PWAT) values up around 2 inches; this climatologically rare setup has been supported by ECMWF ensemble guidance, ranking around the 99th percentile. As one might expect with such a deep and nearly saturated layer, warm cloud depths around 13000 feet look likely, supportive of highly efficient rainfall. Finally, and perhaps most impressively, forecast soundings show a nearly stationary Mesoscale Beta Element (MBE) motion vector that results from deep, moderately weak, and highly uniform flow from the altitude at which the low level jet typically resides all the way through the entire storm bearing layer. This is very favorable for quasi-stationary back- building MCSs...a preview of which we have already seen earlier today across north TX near the Red River (please reference recent WPC Mesoscale Precipitation Discussions).

The best upper PV forcing and plume of greatest PWAT may still be slightly upstream at this time, more towards WI, but we still expect convection to enter far southwest Lower MI around midnight Monday night and this activity could provide a requisite MBE-caliber surface boundary to later serve as an anchor point for locally heavy rain.

The focus for heavy rain continues and perhaps even increases through Tuesday as the aforementioned forcing and PWAT plume both cross Lower MI.

Thunderstorm chances around 30 percent continue late Tuesday night into Wednesday night as a northern Plains upper trough slowly approaches and provides a steady stream of difluent flow aloft and implied synoptic ascent coupled with it.

- Thunderstorms, some severe, likely Thursday/Thursday night

The previously mentioned northern Plains upper trough is forecast to break cyclonically across the western Great Lakes. Moderately strong southwesterly lower tropospheric flow will yield 0-3 km bulk shear around 30 knots around the same time ECMWF ensemble mean MUCAPE climbs to 3000 J/kg. Some mid-level drying will enhance DCAPE as well, meaning that damaging winds associated with multicell clusters will be possible from late Thursday into Thursday night. Temperatures and apparent temperatures could get quite warm prior to convective initiation, but the duration should be curtailed at least some.

- Possibly dry Friday, then a chance of storms this weekend

Flow aloft behind the breaking upper trough becomes zonal and then west-southwesterly, offering many opportunities for transient upper PV maxima to provide forcing for additional deep convection. But, predictability with identifying (let alone timing) features such as these tends to be very poor in a season that already has poor predictability. It is therefore not surprising that ensemble solutions are trending towards what are basically climatological PoPs (20-30 percent) during the weekend.

AVIATION /00Z TAFS THROUGH 00Z TUESDAY/

Issued at 650 PM EDT Sun Jun 7 2026

VFR conditions expected through approximately 18z-20z Monday with only some high clouds and E to ESE winds overnight. Beyond 18z Monday, expecting a progressively BKN sky with cloud bases lowering down to at least 6k-7k ft as some showers and scattered thunderstorms develop across northern IN and extreme SW Lower MI especially after 20z and toward the end of this TAF period. AZO would likely be experiencing the earliest onset of rain based on afternoon model guidance. Timing will be fine tuned with subsequent model cycle updates.

MARINE

Issued at 203 PM EDT Sun Jun 7 2026

No marine headlines are anticipated through at least Tuesday, although marine fog may be an issue once again mainly over the open waters tonight. Thunderstorms enter the area Monday afternoon with better chances Monday night into Tuesday. Additional chances for storms exist for Wednesday and Thursday.

The next chance for Small Craft Advisory (SCA) conditions looks to be Wednesday into Thursday with stronger southwest winds. The longer fetch areas associated with this wind direction (generally from Grand Haven northward) can expect SCA conditions along with potentially high risk swim conditions.

GRR WATCHES/WARNINGS/ADVISORIES

MI...None. MARINE...None.