textproduct: Grand Rapids

KEY MESSAGES

- Showers and isolated thunder today

- Small chance of weekend showers

- Higher chance of showers/storms Monday

DISCUSSION

Issued at 248 AM EDT Wed Sep 9 2026

- Showers and isolated thunder today

Not much change to the going forecast. Radar shows light showers moving east across Lower MI and extending west to Nebraska. Given MUCAPE only around 100 j/k, it's no surprise there isn't much lightning around. However, HRRR shows SBCAPE increasing to several hundred j/kg by this afternoon and so isolated thunder remains a possibility. Current shear values are around 20kts but progd to increase to 40-50 kts this afternoon. Thus, a few showers or isolated thunderstorms may be able to produce some gusty winds, but instability remains lacking. Moisture isn't though. PWATs remain high...aoa 2 inches and so locally heavy rainfall remains possible. Once the cold front moves through after 18z, we'll see the showers move southeast with it. Skies will clear late in the day.

- Small chance of weekend showers

High pressure will create a couple of dry days tomorrow and Friday before the next cold front moves through. Not a lot of change there either. It's a weak front with not much of a thermal gradient and the accompanying low will be near James Bay. Moisture return ahead of it is anemic and so PoPs remain low; much of the weekend will be dry. Highs will be in the upper 70s to around 80, but dewpoints will remain in the mid to upper 60s creating humid conditions.

- Higher chance of showers/storms Monday

A strong short wave moving onshore over the Pacific NW will move east this weekend creating a northern Plains low that will drag a cold front across Lower MI early next week. this short wave is progd to be fairly potent and so showers and thunderstorms will be in the forecast Monday into Tuesday.

Models show a 50kt LLJ Monday afternoon coupled with PWATs aoa 2 inches and 40-50kts of shear along with SBCAPE around 1200 j/kg. Those are decent dynamics for storm development and we'll continue to keep an eye on this potential development.

AVIATION /12Z TAFS THROUGH 12Z THURSDAY/

Issued at 630 AM EDT Wed Sep 9 2026

Showers and isolated thunderstorms are moving across Lower MI early this morning. We're in a little bit of a lull that was seen in the convective models. Regional radar shows more rain upstream. We'll continue with the showers in the TAFs into the afternoon. Didn't include thunder, however, instability does increase a bit this afternoon and thunder is possible.

Precipitation will end later this afternoon and skies will become partly cloudy. Fog will likely form after midnight due to clearing skies and residual moisture from the rain and IFR conditions are possible late in the period.

MARINE

Issued at 248 AM EDT Wed Sep 9 2026

We're continuing with the small craft advisory and including all zones from St Joe to Manistee. While waves wont' be particularly high south of Holland, winds will increase to 15 to 25 knots this morning which will make for hazardous conditions. No change to the ending time of the advisory.

Another small craft advisory may be needed Saturday as another cold front moves through the region.

GRR WATCHES/WARNINGS/ADVISORIES

MI...Beach Hazards Statement through this evening for MIZ037-043-050- 056-064-071. MARINE...Small Craft Advisory until 8 PM EDT this evening for LMZ844>849.