textproduct: Grand Rapids

KEY MESSAGES

- Small chances of showers/storms through Friday; Mainly South

- Periods of showers/storms likely Friday night into Sunday

- Cooling off and drying out Monday through most of Wednesday

DISCUSSION

Issued at 309 AM EDT Thu Aug 13 2026

- Small chances of showers/storms through Friday; Mainly South

As has been the case the past couple of days, the main ring of fire convection axis has remained south of our forecast area. This is the result of the stalled out boundary keeping the very hot and humid conditions well south of the state, and the sfc waves riding along it.

The models continue to show at least a couple of additional clusters of storms just missing us to the south again. Based on the pattern the last couple of days without any big push northward, this seems very likely. Especially with another weak front dropping south through the area early this morning. Can not rule out some rain along the far southern edge of the forecast area on the northern edge of any cluster.

- Periods of showers/storms likely Friday night into Sunday

We do see some changes in the pattern showing up beginning Friday night, and lasting into Sunday. This change in the pattern is facilitated by a long wave trough taking hold over the Western third of the country. This wave then ejects a couple of short waves and sends them via a more SW flow aloft toward the area.

This pattern shift then also pushes the boundary further north, bringing the higher heat and humidity closer to the area. With short waves riding along this front, we will see MCS activity ramp up once again with the associated low level jets traversing over our southern area, or staying just south and the nose of them aiming toward the area. We will need to keep an eye on this as we could see strong to severe storms be possible while we are under the theta e axis and short wave train.

This really looks possible from Friday evening all the way into Sunday. On Sunday, we see a general trend in the pattern showing that everything sinks south as the SW flow aloft and upper ridge gets flattened a bit. This includes the baroclinic zone and active zone for MCS activity, along with cooler weather filtering in.

- Cooling off and drying out Monday through most of Wednesday

The front will sink south through the area no later than Sunday, taking with it the moisture and instability, and shunting it to our south by Monday. Upper and sfc ridging will build in for Monday through at least early Wednesday, keeping us dry. There are some indications the next wave could come in late next Wednesday. We have time to fine tune the timing of this.

AVIATION /12Z TAFS THROUGH 12Z FRIDAY/

Issued at 653 AM EDT Thu Aug 13 2026

Dense fog has definitely impacted all of the forecast terminals this morning with VLIFR conditions at all of the terminals. This fog will linger until about 13-14z and then mix out/burn off quickly.

Once the fog is gone, we anticipate mainly VFR conditions for the rest of the forecast period. There may be a shield of mid clouds that come in with a storm complex later this afternoon. Have added a PROB30 for KAZO and KBTL for some showers. All of the thunder should stay south.

MARINE

Issued at 309 AM EDT Thu Aug 13 2026

No wind or wave headlines are expected through at least Friday. The pattern we are in through Friday is that of a weak pressure pattern, resulting in lighter winds and waves. We can not rule out needing some fog headlines given the weak winds and moist air mass.

There is some uncertainty as to when the winds and waves may be strong enough to necessitate Small Craft Advisories and Beach Hazard Statements. The latest trend is for better winds aloft moving overhead Friday night, However being warmer winds, those may very well stay aloft. The potential for winds and waves will last through much of the weekend until the system moves far enough away.

GRR WATCHES/WARNINGS/ADVISORIES

MI...Dense Fog Advisory until 10 AM EDT this morning for MIZ050-051- 056>059-064>067-071>074. MARINE...None.