textproduct: Grand Rapids

KEY MESSAGES

- Periods of showers and thunderstorms through Saturday

- Chances for showers and storms Monday night into mid week

- Warm and humid next week

DISCUSSION

Issued at 313 PM EDT Fri Jun 5 2026

- Periods of showers and thunderstorms through Saturday

Several rounds of showers and storms are expected across Southwest Lower Michigan between this afternoon and Saturday evening. The first threat comes this afternoon and evening as a mesoscale convective vort (MCV) moves northeast through the forecast area. The leading edge of this vort max has become diffuse with time, but is situated near mid lake over the southern bowl of Lake Michigan. Little in the way of convection is ongoing at this time associated with it. Most unstable CAPE values are only around 500 j/kg at this time, which is probably the main reason we are not seeing more activity develop. This is due to fairly widespread showers today along with lingering cloud cover. There are a few breaks in the overcast for additional heating, but there are not many. Overall feeling the threat this afternoon and evening is fairly low given the lack of building instability. Not out of the realm of possibilities though that we could see a few strong winds gusts if storms can organize. We will be watching.

Tonight, instability actually builds in a southwest flow as unstable air is advected in southwest flow ahead of a cold front. We are expecting MUCAPE values to reach the 1000-2000 j/kg range despite the time of day. This is owed to the deep moisture that moves in. Tonight's convection actually has more going for it with better dynamics in play. A shortwave moves in from the northwest which will be driving a cold front into the unstable airmass over our area. Deep layer shear is roughly 30-40 knots so severe weather is very much possible. Actually all hazards are in play tonight.

The severe weather threat may continue towards daybreak in Southern Lower Michigan towards I-94 as the deep moisture remains in place ahead of the cold front. There may be just enough time to rekindle a few storms near I-94 again into the midday hours before the cold front sweeps south. The main threat may actually be the overnight convection though after midnight.

- Chances for showers and storms Monday night into mid week

The upper pattern for several days in a row now has shown shortwave troughing trying to move into the mean ridge position across our area. Hard to ignore this continuity. We have chances for showers and storms from Monday night at least into mid week.

- Warm and humid next week

Warm and humid conditions are expected all next week. 80s for highs will be common and we will push into the 90s late in the week. The ECWMF is not as warm as it was a few days ago at 850mb on Thu/Fri as 24-25C has come down to 21-22C. Bottom line it is going to feel like summer, but maybe not quite as warm as we were thinking.

AVIATION /06Z TAFS THROUGH 06Z SUNDAY/

Issued at 140 AM EDT Sat Jun 6 2026

Scattered showers and thunderstorms are moving through the area causing various flight conditions from IFR to VFR. Expect conditions to bounce around through 9Z before storms shift south of the area. Heavy rain is likely with any thunderstorm and stronger storms may produce a brief burst of stronger winds 40 to 50 knots.

After 12Z conditions are expected to improve to VFR. Isolated storms are possible during the late morning and early afternoon before the front moves through. Confidence in thunderstorms impacting any one airport is low, but have included Prob30s where confidence is a little higher at JXN and LAN.

MARINE

Issued at 313 PM EDT Fri Jun 5 2026

Have opted to drop the Small Craft Advisory and the Beach Hazards Statement as conditions are below criteria at this point and not expected to make a significant increase this evening. There may be some 3 footers for a time this evening near Muskegon, but all the nearshore buoys to the north right now are indicating 1-2 foot waves. The gradient gets more slack as we head into tomorrow, so we should remain below advisory thresholds heading into the weekend.

GRR WATCHES/WARNINGS/ADVISORIES

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