textproduct: Grand Rapids

KEY MESSAGES

- Convective trends remain the main forecast concern

- Heat continues into the holiday weekend

DISCUSSION

Issued at 412 AM EDT Thu Jul 2 2026

- Convective trends remain the main forecast concern

A quasi-stationary front drove convection upstream yesterday evening and into the overnight hours. This activity moved into far northern sections of the forecast area yesterday evening and into tonight. For our area we remain on the warm side of the boundary with around 2,000 j/kg of MUCAPE at 400am. Confidence in storm morphology remains on the lower side overall. A strong low level jet is in place overhead this morning which is usually a driver of additional storms. The SPC HREF does indicate a round of convection during the morning and into the midday hours between roughly 10am and 2pm. We are in a marginal to slight risk for severe weather today via the SPC and this is largely tied to the level of instability that will be in place. Some stronger winds in the profile will make damaging winds the main threat. Another round of storms is expected this evening. Heavy rain is also very possible today with high PWAT air in place and a boundary to focus the storms.

We remain in a threat for severe weather both Friday and Saturday with the SPC having us in a marginal threat both days. Convection will be driven by a stationary front remaining in the area and mid level MCV's floating through the region to enhance the threat. Again, confidence is on the lower side with regard to how storms evolve each day. Heavy rain will remain a threat on Friday and Saturday as the airmass will largely remain the same.

- Heat continues into the holiday weekend

GFS MOS numbers look more reasonable which keeps temperatures in the 90s today, Friday and Saturday (or at least near 90). We "cool" back into the 80s for highs on Sunday and into early next week. Will maintain the current Heat Warning as is, but we may need to extend it into Friday at least.

AVIATION /12Z TAFS THROUGH 12Z FRIDAY/

Issued at 653 AM EDT Thu Jul 2 2026

The main concern remains the threat of thunderstorms today. Confidence in how storms evolve today remains low, but we feel there are two main time frames that could affect aviation interests in this TAF period. The first is from mid morning into early afternoon, roughly 14z through 19z. This threat is most likely tied to the ongoing batch of showers/storms over Lake Michigan. This activity looks to remain on the smaller side in terms of aerial coverage, but I-96 TAF sites look to be the favored location. A second round of storms looks to press in from the west after 00z. These storms will be more widespread and may have a risk of stronger thunderstorms winds in excess of 40 knots. Do not have that level of wind in the TAFs at this point given low confidence.

Otherwise, look for southwest winds to become gusty this afternoon at 10-20 knots with some gusts to around 25 knots.

MARINE

Issued at 412 AM EDT Thu Jul 2 2026

We were previously thinking that winds and waves would be near advisory criteria levels at this time, but that has not panned out early this morning. Winds are well below criteria at this point with many sites falling below 10 knots. Buoys at present are indicating 1 foot waves. So, no need to issue any headlines this morning given current conditions and what the rest of today and tonight look like. We may see conditions come up to a moderate swim risk today, otherwise we are heading into a lighter wind regime as we move into and through the holiday weekend.

GRR WATCHES/WARNINGS/ADVISORIES

MI...Extreme Heat Warning until 8 PM EDT this evening for MIZ037>040- 043>046-050>052-056>059-064>067-071>074. MARINE...None.