textproduct: Grand Rapids

KEY MESSAGES

- Predominantly dry this weekend

- Major to extreme heat risk next week

- Chances for showers and storms next week

DISCUSSION

Issued at 220 PM EDT Fri Jun 26 2026

- Predominantly dry this weekend

Radar currently shows rain showers crossing southern Lake MI and moving east towards the I-94 corridor. Showers generally from I-94 southward will be possible this afternoon and evening.

After this, forecast certainty for a dry weekend is very good (90 percent) thanks to a amplifying upper ridge over the Upper Mississippi Valley region. This will supply synoptic scale subsidence to the western Great Lakes and this will be complemented by a lack of low level forcing for ascent. Temperatures will gradually warm.

- Major to extreme heat risk next week

Expectations for dangerous heat next week have not changed much. Afternoon heat indices should easily exceed 100F starting Tuesday and this should last through at least Thursday. The hottest day may be Thursday, with heat indices exceeding 105F for most areas east of US-131. In fact, the southern US-127 corridor, including Jackson and Lansing, could exceed 110F.

To compound the risk, and as noted previously, dewpoints in the 70s will keep minimum temperatures in the mid 70s. The prolonged heat and humidity will test the resilience of vulnerable populations not having access to proper air conditioning, so now is a good time to start planning for checking up on those at risk.

Heat safety tips and resources can be found by visiting: weather.gov/heat

- Chances for showers and storms next week

Precipitation chances are challenging because with the heat and humidity comes persistent and substantial conditional instability. Even for the overnight hours, southern Lower MI could see MUCAPE easily remaining above 2000 J/kg. This is plenty sufficient for convective maintenance of upstream MCSs over WI that develop the prior evening/afternoon and move into the area. For this reason, our northwestern zones will maintain at least a slight chance of showers and thunderstorms through the period. Nocturnal MCSs are notoriously difficult to model, but given their tendency to propagate towards the greatest instability, it is highly plausible that even areas along and south of I-96 could see activity rolling in from the north-northwest almost any day of the week, most likely during the overnight or early morning hours. So, our currently advertised low PoPs during this time do come with a bit of a caveat.

Thunderstorm chances climb somewhat Thursday/Friday and into the Fourth of July weekend as several of the deterministic solutions show the upper ridge breaking down due to cancelling effects of at least one minor shortwave trough moving through. From a QPF standpoint, successive runs of the ECMWF ensemble and AI guidance have not been particularly consistent. Hence, predictability remains very low. It is plausible that the heat and humidity continue unabated into the holiday weekend without temperatures being mitigated much by precipitation. On the other hand, nighttime precipitation could give afternoon dewpoints a boost into the upper 70s, thus greatly increasing the daytime heat risks.

Given increased exposure/vulnerability to multiple hazardous weather concerns during next weekend, we will be watching this very closely in the coming days.

AVIATION /06Z TAFS THROUGH 06Z SUNDAY/

Issued at 126 AM EDT Sat Jun 27 2026

Occasional MVFR at KJXN during the first 6 hours of the TAF period. Otherwise...expect VFR conditions at the terminals into Saturday night.

MARINE

Issued at 220 PM EDT Fri Jun 26 2026

No concerns this weekend, although localized marine fog is not out of the question. By Sunday night, dewpoints are expected to have climbed to the mid/upper 60s F, which should exceed nearshore water temperatures. However, strengthening offshore flow might keep the incipient fog threat shunted out more towards mid-lake. Wave growth will also be underway Sunday night as well with the stronger winds. Areas north of Muskegon will likely require Small Craft Advisory headlines through at least Monday.

GRR WATCHES/WARNINGS/ADVISORIES

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