288 FXUS63 KGRR 180812 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 412 AM EDT Sat Apr 18 2026 .KEY MESSAGES... - Cooler For A Few Days, Then Warming Back Up Mid-Late Week && .DISCUSSION... Issued at 412 AM EDT Sat Apr 18 2026 - Cooler For A Few Days, Then Warming Back Up Mid-Late Week Welcome relief from the recent rainy pattern as a progressive synoptic trough over Canada and the northern CONUS sweeps a cold front through this morning, with 850 mb temperatures expected to cool 20 C in 24 hours, between early this morning and early Sunday morning. A shortwave digging into the backside of the trough over Michigan on Sunday may support some wet snow showers. The coldest air, down to -10 C at 850 per the ECMWF, will be in place underneath a center of high pressure Sunday night. As a result, lows in the 20s are favored Sunday night / Monday morning. Note, we will begin the frost/freeze headlines for Muskegon, Kent, Montcalm, Gratiot, and south. High temperatures Sunday and Monday are favored to be in the 40s, about 10-15 degrees below normal. Ensembles do have pretty good agreement on temperatures rebounding into the 60s Tuesday as the synoptic wave pattern progresses eastward and southwesterly flow brings warmer air back. Most ensemble members have temperatures peaking for the week on Thursday with highs well into the 70s. Instability may build again Thursday and Friday with a chance of thunderstorms, followed by a a chance of a cooling trend for the weekend. && .AVIATION /06Z TAFS THROUGH 06Z SUNDAY/... Issued at 239 AM EDT Sat Apr 18 2026 The line of thunderstorms traveling from west to east will continue to impact KGRR, KAZO, and KBTL through around 08Z, and impact KLAN and KJXN from 07Z-10Z. Thunderstorms may contain gusts 25 to 35 knots. MVFR ceilings move in with the thunderstorms and may fall to IFR levels briefly into Saturday morning. Low visibilities of 1 to 3 SM are also likely during heavy rain. Low level wind shear of 40 to 50 knots will be present as a low level jet impacts the area through 12Z Saturday. Northwest winds behind the front will build through the day with gusts 25 to 30 knots, followed by a decrease in winds after 01-03Z. Ceilings will also begin to lift and scatter out Saturday afternoon and evening. && .MARINE... Issued at 412 AM EDT Sat Apr 18 2026 Colder air flowing in behind a cold front with west winds gusting 25-30 knots will build 3-6 ft waves today into Sunday morning. Lower waves are expected Sunday night into Monday with lighter winds as high pressure moves over the region. && .HYDROLOGY... Issued at 253 PM EDT Fri Apr 17 2026 Major flooding continues on the Muskegon River. The good news is that the river at most locations will be cresting within the next 24 hours (Upstream areas of the river including Evart crested earlier today). It will likely take until late next week for all locations to come under flood stage, so the recovery process will be slow. Meanwhile, water levels continue to rise on the Grand River, and confidence is increasing that this will end up being another minor flood event, slightly higher and worse than the one that happened earlier this month, but not a record flood at any locations. However, some of the lowest and easily flooded locations on the river like Comstock Park and Robinson Township will have moderate to possibly major flooding. A final round of rain moves back into Lower Michigan tonight, and is expected to drop around one-half inch of rain over a large area, with locally higher streaks of 1"+ possible at some locations. Given the saturated soils everywhere, this could result in some renewed minor flooding, primarily impacting roadways. Thankfully, this expected rainfall is not anticipated to make the river flooding significantly worse at any locations. Beyond this next round of rain, we dry out for at least the better part of a week going forward, which will be a very welcome chance for the rivers to begin the slow process of recovering to more normal levels. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...Small Craft Advisory until 8 AM EDT Sunday for LMZ844>849. && $$ DISCUSSION...CAS AVIATION...Schoenfeld MARINE...CAS HYDROLOGY...AMD

NWS GRR Office Area Forecast Discussion