textproduct: Grand Rapids

KEY MESSAGES

- Mostly dry through much of Friday

- Rain possible on Sunday with the tropical system

- Turning much colder next week with a strong front late Monday

DISCUSSION

Issued at 200 PM EDT Wed Oct 7 2026

- Mostly dry through much of Friday

We remain in the same pattern for another 24-36 hours as we have seen much of this week thus far. That pattern is one where the northern branch of the upper jet is centered north of the area with a flow from the WNW. The upper jet is just close enough that we are seeing additional cloud cover with weak short waves passing by to our north. A lack of cloud cover and deep instability is keeping us mainly dry, except for a few sprinkles.

The latest set of model guidance is keeping most of any sprinkles just north of the forecast area border through much of the day on Friday. We see a change with the upper air pattern at that time with upper flow taking on a more WSW flow with the ridge lifting up toward us. As this occurs, a sfc warm front will be moving through Friday evening, and will increase the chance of rain some for much of the area. This is still a low chance, as moisture below 8k ft is still quite limited.

This will set the stage for a warm October day with widespread 70s, and maybe an 80 degree reading or two across the south away from Lake Michigan.

- Rain possible on Sunday with the tropical system

We have been watching the evolution of forecasts with the Tropical system Isaias over the past few days going from missing the area completely to the SE, to now possibly bringing some rain in across southern Lower Michigan on Sunday.

This has been complicated as there is a non-tropical upper low over SE Texas, and a long wave trough coming in from the West Coast. Initially, Isaias was being pushed to the NE quickly with the long wave trough. Now the upper low over TX absorbs Isaias and rotates almost due north before the upper wave comes in and sweeps it out. As has been mentioned the past few days, rotating upper low tracks are difficult to forecast. The trend has definitely been for a better chance for rain, as the system goes extra-tropical and looks more like a mid-latitdue system.

- Turning much colder next week with a strong front late Monday

However the system moves in Sunday, and any rain that falls will be on its way out by late Sunday. We will see a narrow upper ridge build in briefly between the extra-tropical system, and the larger trough coming in from the NW. This trough will have reinforcement coming in from the NW. The front will move in Monday evening, and pass through Tuesday. The strong forcing ahead of this trough will bring a bout of rain to the area.

Behind the system on Tuesday and beyond, we will see a fairly decent Canadian high set up and bring some much cooler air in over the area. Highs are likely to be only in the 50s, and some lake effect rain will be possible.

AVIATION /18Z TAFS THROUGH 18Z THURSDAY/

Issued at 106 PM EDT Wed Oct 7 2026

A weak cold front is moving across the Lower Peninsula early this afternoon. Virtually no clouds accompany the front, just a minor wind shift. Clear skies are expected through the period.

MARINE

Issued at 200 PM EDT Wed Oct 7 2026

We are cancelling the Small Craft Advisory that has been in effect the last couple of days. We will be turning around and issuing the next Advisory for this evening and Thursday morning. We are in a brief reprieve between events right now with waves having dropped below 4 ft. This is associated with a weak ridge moving through this afternoon.The gradient will tighten up enough in its wake beginning this evening, to require another advisory be issued. This will last through Thursday morning before waves come down enough.

We will see another break in the wind and wave action later Thursday through Friday morning, before winds come up again behind a warm front that will be moving through the area late Friday. Winds will hold up then through Saturday night.

GRR WATCHES/WARNINGS/ADVISORIES

MI...None. MARINE...Small Craft Advisory from 8 PM this evening to noon EDT Thursday for LMZ844>849.