textproduct: Grand Rapids

KEY MESSAGES

- Air quality concerns remain through Friday with slightly cooler air

- Shower and storm chances Friday p.m. and first half of Saturday

- Better rain chances late Monday into Tuesday; then much cooler

DISCUSSION

Issued at 240 PM EDT Thu Jul 16 2026

- Air quality concerns remain through Friday with slightly cooler air

Bottom line upfront is: In coordination with Michigan Environmental, Great Lakes, Energy (EGLE), the smoke is expected to remain prevalent an very unhealthy to hazardous through most of Friday. The smoke has spread across the entire state now behind the weak cool front that dropped through late yesterday. The wind fields remain weak, and what wind there is continues to draw down better smoke concentrations from the north for the time being.

We do not see a major change in the situation until likely later Friday. At that time, we see a large scale increase in the wind from the SW ahead of the next incoming front poised to move through Saturday. Smoke models that have had a clue with this smoke event indicate that these winds will try to push the smoke out Friday evening. Whether that is it for the smoke for this event is very uncertain due to what happens with the fires over NE MN and Ontario, what smoke plumes do, and then how the smoke plumes move with the passage of the system.

- Shower and storm chances Friday p.m. and first half of Saturday

Back to the actual weather, we look to remain dry through tonight, before rain chances arrive Friday morning across Central Lower, and Friday afternoon for the southern half of the area.

We see a weak short wave traverse from Northern Minnesota and to over Lake Superior and the U.P. tonight. The tail end of the few showers/isolated storms could clip our far northern portion of the area Friday morning. Obviously with a lack of diurnal heating, there will not be much of a threat of anything strong.

We will then see the shower/storm chances shift from the north early, to the south later in the afternoon. We see the front that moved through yesterday return northward as a warm front Friday afternoon/evening. The southern half of the area away from Lake Michigan will see MU CAPEs increase to over 2000 J/kg. Deep layer shear is quite limited, to less than 20 knots, so any storms will be pulse type in nature.

We will lose the diurnal heating and rain chances Friday evening, until Saturday morning with the approach of the front. This front will be accompanied by the tail of a short wave. However, the timing is not very good as it looks to move through most of the forecast area by 18z Saturday. We do expect showers and storms to develop ahead of the front, but probably won't get going to halfway through the forecast area. The much better chance of more widespread showers/storms, and severe weather will be further SE where better heating can take place before it moves through.

- Better rain chances late Monday into Tuesday; then much cooler

Sunday looks to be mainly dry, and fairly warm again as there is not much cooler air behind the Saturday system. Dew points/moisture will tank a bit to limit instability.

We will end up under NW flow aloft by then, and into early next week. This flow pattern will bring the next noticeable system to approach the area by late Monday. There is a series of 2-3 short waves that will drive a front down into the area. The first one will help bring a warm front up into the area Monday night, and then a cold front come in early Tuesday. Then, the next upper wave approaches Tuesday afternoon. These will bring the better chances of rain to the area from Monday night through much of Tuesday.

The upper trough axis then moves by late Tuesday, and a long wave ridge builds well west of the area. This will bring much drier and cooler air for mid-late week next week.

AVIATION /18Z TAFS THROUGH 18Z FRIDAY/

Issued at 149 PM EDT Thu Jul 16 2026

Local surface observations continue to indicate IFR and even LIFR horizontal visibility restrictions in smoke along with MVFR broken "cloud" layers that are in reality associated with vertical visibility restrictions in smoke. It is possible that terminals experiencing LIFR visibility restrictions will temporarily rise into the 1+ mile range this afternoon; however, predictability with smoke and its light scattering effects are very limited. To illustrate: our chief guidance source for these situations, the HRRR-smoke model, has been under-forecasting the severity of visibility restrictions thus far, which does not bode well for significant improvements in the short term, or even for the full valid period of this TAF package.

The only change of note was to introduce a period of northwest winds this afternoon. But even this could be affected somewhat by atypical diurnal heating effects (and subsequent surface pressure responses) associated with the smoke.

MARINE

Issued at 240 PM EDT Thu Jul 16 2026

Main marine issue initially is the wildfire smoke over the entire area. The current thought is the smoke will remain largely unchanged through Friday, until winds from the SW increase a bit and potentially push the smoke to the NE. This was the reasoning for extending the Dense Smoke Advisory earlier over the entire nearshore through Friday evening.

Speaking of the increase in wind late Friday, right now it looks to remain just below Small Craft Advisory criteria ahead of the cold front. The better chance will be behind the cold front as slightly cooler air moves in along with the ridge pushing in.

GRR WATCHES/WARNINGS/ADVISORIES

MI...Air Quality Alert until midnight EDT Friday night for MIZ037>040- 043>046-050>052-056>059-064>067-071>074. MARINE...Dense Smoke Advisory until 8 PM EDT Friday for LMZ844>849.