856 FXUS63 KGRR 161749 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 149 PM EDT Thu Jul 16 2026 .KEY MESSAGES... - Poor Air Quality and Reduced Visibilities From Smoke Thursday - Several Chances of Showers and Storms Through Early Next Week - Temperatures Cooling Through Early Next Week && .DISCUSSION... Issued at 230 AM EDT Thu Jul 16 2026 - Poor Air Quality and Reduced Visibilities From Smoke Thursday Primary forecast concern over the next day is impacts from near- surface and aloft wildfire smoke across the area. ASOS observations show widespread visibilities in the 1-3SM range as a result of smoke. Some areas across Lower Michigan have fallen as low as 1/2SM at times in the last 24 hours, and cannot rule out similar conditons here as another pocket of near-surface smoke arrives near daybreak. HRRR/Canadian smoke guidance shows near- surface smoke persisting through the day today. Air quality observations show unhealthy to locally hazardous conditions, and an Air Quality Alert remains in effect areawide from Michigan`s Department of Environment, Great Lakes, and Energy. - Several Chances of Showers and Storms Through Early Next Week A series of fronts and shortwaves drive several shower and thunderstorm chances through early next week. First is Friday with a warm front crossing the area. However, low-level moisture quality is poor limiting precipitation potential. A cold front Saturday brings greater potential for showers and storms, along with ample CAPE and decent kinematics. However, ample MLCIN will help put a check on storm development, with the best chance east of US-127 into southeast Michigan. Given the ample CAPE/Shear, any storms that develop could be strong to severe, so forecast trends will need to be monitored. Another cold front Monday Night into Tuesday brings a third round of shower/storm chances to the area. - Temperatures Cooling Through Early Next Week 850mb temps will fall from near 20C over the next day or two to the low to mid teens by mid next week. This will cause highs to fall from the low 90s Thursday/Friday to the low 80s by early next week. With lower post-frontal dewpoints expected after the front bringing smoke to the area tonight, heat indices will be limited to the 90s, cooler than previous days. && .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 645 AM EDT Thu Jul 16 2026 Webcams show widespread dense smoke north of Holland with smoke starting to become dense south of Holland. In collaboration with other Lake Michigan offices, have issued a Dense Smoke Advisory through early afternoon. Will let day shift reassess to see if an extension is needed as daytime mixing develops. --- Previous Discussion Issued 230 AM EDT Thu Jul 16 2026--- Widespread smoke is expected across the waters with visibilities below one mile possible at times. If confidence increases in lower visibilities a Marine Dense Smoke advisory may be needed. Between Friday morning and Saturday, a series of fronts bring the potential for isolated thunderstorms over the waters. In addition, strengthening northwest flow is expected to develop Saturday, causing waves to build to at least 3-5 ft. This makes it likely conditions will be hazardous to small craft and boaters. && .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. && $$ DISCUSSION...Thomas AVIATION...TJT MARINE...Thomas

NWS GRR Office Area Forecast Discussion