926 FXUS63 KGRR 250543 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 143 AM EDT Sun Oct 25 2026 .KEY MESSAGES... - Fog Possible Late Tonight into Sunday Morning - Cooler Early Week Period, Then Warming Again - Chance for Showers Late Week && .DISCUSSION... Issued at 152 PM EDT Sat Oct 24 2026 - Fog Possible Late Tonight into Sunday Morning There is another risk for fog beginning late tonight especially east of US 131. NBM hourly guidance indicates dew point depressions near zero, RH values close to 100%, and wind speeds less than 5 mph. HRRR soundings at LAN and JXN show solid low level temperature inversions with light winds through the stable layer. As a result, it seems probable that at least patchy if not numerous areas of fog may develop once again tonight mainly closer to 06z and possibly lasting to 14z or so. The best risk is near and east of a Big Rapids to Battle Creek line. - Cooler Early Week Period, Then Warming Again Relative to the temperatures we`ve had over the last week, cooler readings move in Monday into Tuesday as a cold front swings through the state and winds shift out of the north and then northeast. This front should move through dry. Highs across central Lower MI dip into the mid to upper 50s each day while southern Lower MI stays more in low to mid 60s. From Wednesday through Halloween, ensemble guidance favors upper 60s to low 70s each day, well above normal for the end of October. - Chance for Showers Late Week An increasing low level jet late Wednesday ahead of a trailing cold front associated with a deepening low over Ontario may bring some showers to the region as early as late Wednesday, lingering into Thursday. Probabilities are currently 20-40% for this to occur, with the highest likelihood near and west of US 131. Too early to determine if Halloween may stay dry or not. Ensemble guidance`s individual member QPF shows a more active signal late next weekend into early November for a rather wet pattern. Whether this impacts Halloween remains to be seen. A period of anomalously high PWAT values may move in by late next weekend with perhaps enough instability to support a chance for thunderstorms. && .AVIATION /06Z TAFS THROUGH 06Z MONDAY/... Issued at 143 AM EDT Sun Oct 25 2026 Areas of fog remain the main concern through 14 Z. At 06 Z, the thickest fog can be seen on nighttime microphysics satellite images vicinity east of JXN with a north-northwest movement. This has been where the REFS has been picking up on the greatest fog potential. Confidence is reasonably high in JXN being near minimums much of the early morning. IFR mist or fog may be relatively shallow or patchy at other terminals. && .MARINE... Issued at 730 PM EDT Sat Oct 24 2026 Southerly winds around 10 to 20 knots are expected into Sunday. A front will move through Sunday night into Monday with winds shifting to the northeast. Wave heights around 1 to 3 feet are expected before dropping below 2 feet Sunday night. Wednesday southerly winds return. Gusts may approach Small craft Advisory levels with wave heights nearing 4 feet north of Whitehall. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ DISCUSSION...Hoving AVIATION...CAS MARINE...RAH

NWS GRR Office Area Forecast Discussion