textproduct: Grand Rapids

KEY MESSAGES

- Rain and Thunderstorms This Afternoon into Tuesday, Hot Wednesday

- Chances for Storms Wednesday Night through Thursday Night, Severe Possible

- Dry Friday, but Rain and Thunderstorm Chances Return for the Weekend

DISCUSSION

Issued at 307 AM EDT Mon Jun 8 2026

- Rain and Thunderstorms This Afternoon into Tuesday, Hot Wednesday

An active stretch of weather is expected this week starting with later this afternoon into Tuesday.

The shortwave trough over Missouri will slowly move northeast bringing with it plenty of moisture with precipitable water values around 2 inches. Instability will be increasing through the day with MUCAPE values around 500 to 1000 J/kg continuing overnight. While severe thunderstorms are not expected, localized heavy rainfall is possible. In this high moisture environment any thunderstorm will produce heavy rainfall rates. Coverage however will be scattered and areas that see storms linger over the longest or train over repeatedly will have the best chance to see 1 inch or more of rain. The HREF localized probability-matched mean shows pockets of 1 to 3 inch amounts across the forecast area over 24 hour period. These amounts may cause brief localized flooding.

As the shortwave departs Tuesday instability will increase during the afternoon with mean MUCAPE values around 1000 to 1500 J/kg mainly along and east of US-131. We could see some additional thunderstorms as the 850mb front moves through during the afternoon. Some stronger storms are possible with sub-severe winds.

Additional thunderstorms may develop with the warm front late Tuesday night into Wednesday morning, otherwise chances hold off until Wednesday night.

Wednesday looks to be the hottest day of the week with 925mb temperatures around 25 C with highs in the upper 80s to low 90s. Dew points in the 70s would result in heat indices in the 90s with some spots approaching 100.

- Chances for Storms Wednesday Night through Thursday Night, Severe Possible

An advancing upper level trough will bring southwest flow to the area Wednesday through Thursday. This will set the stage for multiple rounds of thunderstorms within a very moist environment. Each round of storms will likely see perceptible water values around 2 inches. The difference with this set up compared to tonight into Tuesday's is that the trough is stronger with upper level jet support along with a stronger low level jet. This will bring the potential for severe thunderstorms with a Mesoscale Convective System (MCS) set up for both Wednesday night and Thursday night. We may be on the edge for Wednesday night as thunderstorms move in from Wisconsin and weaken as they track eastward across the lake into Michigan. The best potential for severe storms will be across western portions of the forecast area with winds as the primary concern.

Depending on how fast we can clear out Thursday morning will determine if we see storms develop during the day ahead of the next MCS Thursday night. The low level jet will not be present during the day but will ramp up again Thursday night bringing plenty of shear with the shortwave trough. Winds will again be the primary concern with the line of thunderstorms.

Both rounds will be capable of heavy rainfall and could lead brief minor flooding, especially in known trouble spots.

- Dry Friday, but Rain and Thunderstorm Chances Return for the Weekend

Dry air moves in behind the thunderstorms Thursday night bringing a break in the rainfall along with cooler temperatures. However rain chances return for the weekend with the upper level trough remaining in the area. The best chances (30 to 50 percent) are Saturday night into Sunday. However the pattern is rather messy, with not much agreement between the various clusters of ensembles. Expect more clarity as we get closer.

AVIATION /18Z TAFS THROUGH 18Z TUESDAY/

Issued at 147 PM EDT Mon Jun 8 2026

No real changes to the inherited TAFs except to refine timing of onset of precipitation tonight based on radar trends and to advertise IFR ceiling restrictions continuing after 12Z Tuesday. These TAFs were already quite verbose due to persistent and hard- to-time probabilities of thunderstorms, so didn't want to add too much detail after 12Z, but the upshot is that precipitation will exit the area from west to east in the 12Z to 18Z Tuesday with a gradual transition to VFR conditions.

MARINE

Issued at 307 AM EDT Mon Jun 8 2026

Waves are expected to remain 2 feet or less through Wednesday morning as winds remain light. Southeast winds are expected through tonight before shifting to the southwest behind the low. Rain and thunderstorms are expected late this afternoon into Tuesday. Expect low visibilities within any thunderstorms as they will be capable of heavy rainfall. The increased dew points over the cold waters of Lake Michigan may also pose a threat for fog as well. We'll need to monitor conditions in case a Marine Dense Fog Advisory is needed.

Winds and waves then pick up Wednesday afternoon into Thursday. Southwest winds gusting to around 25 knots will cause waves to build to 3 to 6 feet especially for areas north of Holland.

GRR WATCHES/WARNINGS/ADVISORIES

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