675 FXUS63 KGRR 181822 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 222 PM EDT Sat Apr 18 2026 .KEY MESSAGES... - Cool Weekend with Frost/Freeze Potential Tonight and Sunday Night - Dry Until Late Week With Warming Temps && .DISCUSSION... Issued at 221 PM EDT Sat Apr 18 2026 - Cool Weekend with Frost/Freeze Potential Tonight and Sunday Night West Michigan currently sits in a post-frontal cold air advection regime with temperatures falling compared to this morning. In sharp contrast to recent warmth temperatures fall tonight as we get an advective freeze event. Temperatures within the mixing layer overnight reach -15C supporting temps in the low to mid 30s through advective freeze processes inland of the marine layer. Have issued a Frost Advisory for all of our counties where the growing season is underway. Clear skies are likely even with 850mb temps approaching LES cloud development levels given that the core of the cold air aloft doesn`t arrive until near diurnal minimum. A more classic freeze event is expected Sunday Night as skies clear out and light winds allow for substantial radiational cooling, with overnight temperatures falling into the 20s. Depending on radiational cooling efficiency there is the potential of this being a hard freeze. Given the recent warmth leading to growing season being well underway across parts of the area and higher confidence in a freeze setup, have issued a Freeze Watch for all areas where the growing season has begun for Sunday Night. - Dry Until Late Week With Warming Temps Large scale ridging and subsidence will support dry conditions continuing through the day on Thursday before a mid-level shortwave and associated surface low bring shower and thunderstorm chances back to west Michigan. 850mb temps climb back into the tens above zero by late week with highs in the 60s by Tuesday and well in the 70s by late week. && .AVIATION /18Z TAFS THROUGH 18Z SUNDAY/... Issued at 213 PM EDT Sat Apr 18 2026 A mix of MVFR and VFR ceilings are in place across Southwest Lower Michigan at 18Z. A cold front is currently moving from west to east across the Lower Peninsula, which should be east of all the TAF sites in the GRR forecast area by 20Z. Improvement to ceilings is expected at all TAF sites as we progress through the afternoon. By 00Z this evening we expect VFR conditions to prevail which should continue through the night. After some clearing overnight, VFR ceilings around 4,000 feet should move back in for Sunday morning beyond 12Z. Gusty winds this afternoon out of the west at 12-25 knots should settle into the 5-10 knot range by 04z tonight. && .MARINE... Issued at 221 PM EDT Sat Apr 18 2026 A Small Craft Advisory remains in effect through Sunday morning. Wind gusts to around 25 knots and 3-6 foot waves continue through the evening and into Sunday morning. Conditions improve for the early part of next week as high pressure moves into the region. && .HYDROLOGY... Issued at 221 PM EDT Sat Apr 18 2026 Major flooding continues on the Muskegon River. The good news is most locations have crested or are cresting now. 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 flooding. Dry conditions are expected through the next several days. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Frost Advisory from 2 AM to 10 AM EDT Sunday for MIZ050>052- 056>059-064>067-071>074. Freeze Watch from Sunday evening through Monday morning for MIZ050>052-056>059-064>067-071>074. MARINE...Small Craft Advisory until 8 AM EDT Sunday for LMZ844>849. && $$ DISCUSSION...Thomas AVIATION...Duke MARINE...Thomas HYDROLOGY...Thomas

NWS GRR Office Area Forecast Discussion