095 FXUS63 KGRR 171021 CCA AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 614 AM EDT Fri Jul 17 2026 .KEY MESSAGES... - Reduced Visibilities and Poor Air Quality From Smoke Friday - Chances of Showers and Thunderstorms Friday Through Saturday - Additional Showers and Storms Possible Monday into Tuesday && .DISCUSSION... Issued at 116 AM EDT Fri Jul 17 2026 - Reduced Visibilities and Poor Air Quality From Smoke Friday For much of the day conditions will be similar to Thursday. Widespread near-surface smoke likely leads to visbys around a mile or less. Leaning on the RRFS-Smoke guidance which has handled things well suggests that dense smoke is possible near daybreak, particularly near US-10 with visbys of under 1/2 mile. Will monitor for a potential Special Weather Statement or Dense Smoke Advisory if this threat materializes, though confidence is low at this time in dense smoke developing. Conditions should begin to improve later Friday into Friday night as southwest flow develops. However, smoke modeling guidance suggests this may be be short lived with additional smoke potentially arriving behind a cold front Saturday. Air quality is also expected to remain at hazardous levels Friday as well. See the latest Air Quality Alert from Michigan`s Dept. of Environment, Great Lakes, and Energy for details. - Chances of Showers and Thunderstorms Friday Through Saturday A few chances for showers and storms exist between late this afternoon/evening and Saturday. First is today`s potential which is associated first with a weak wave that may touch off a few showers across Central Michigan this morning. The threat region then shifts south this afternoon/evening as a warm front arrives. MUCAPE north of 2000 J/kg supports both showers and thunderstorms. However, kinematics are poor with deep layer shear around 20 knots. This will keep any storms pulsey. A shortwave then drives a cold front south across the area Saturday with showers and storms expected to develop across this front. The front should clear the area early Sunday afternoon, however if we can get enough surface based instability development, organized clusters with strong to severe winds are possible given mid-level flow of 40 kts with ample DCAPE. The better chance is south of our area where instability is better. - Additional Showers and Storms Possible Monday into Tuesday High pressure moves into the region behind the front keeping things dry for Sunday ahead of the next system. By later Monday into Tuesday, a series of shortwaves will drive fronts across the area, culminating in a cold front Monday Night into Tuesday. Forecast instability suggests showers and thunderstorms are possible. Northwest flow then marks a cooldown expected into mid-week with highs falling to near 80. && .AVIATION /12Z TAFS THROUGH 12Z SATURDAY/... Issued at 614 AM EDT Fri Jul 17 2026 Visibilities across the terminals fared slightly better than forecast, remaining in the 3/4 to 1 1/2SM range for most. Attempted to add more detail to forecast improvement this afternoon as smoke clears with the introduction of southwest winds. Leveraged HRRR/RRFS guidance, but given the inherent complexities in smoke forecasting confidence is low. Also included PROB30s for thunder at AZO/BTL/JXN as scattered thunderstorm development is possible this afternoon. Thunderstorms may bring MVFR or lower conditions, but would also help clear out smoke. && .MARINE... Issued at 116 AM EDT Fri Jul 17 2026 Dense smoke is expected to continue across the waters through this evening with a Marine Dense Smoke Advisory remaining in effect. Southwest flow then develops tonight with 15-18 knot winds. Right now, it looks to be just below Small Craft/Beach Hazards criteria with 2-4 foot waves likely. We then see another increase in winds behind a cold front with an advancing high later Saturday. Small Craft/Beach Hazards conditions are very likely in this timeframe. Isolated thunderstorms are also possible Saturday morning as this cold front crosses the waters. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Air Quality Alert until midnight EDT tonight for MIZ037>040- 043>046-050>052-056>059-064>067-071>074. MARINE...Dense Smoke Advisory until 8 PM EDT this evening for LMZ844>849. && $$ DISCUSSION...Thomas AVIATION...Thomas MARINE...Thomas

NWS GRR Office Area Forecast Discussion