783 FXUS63 KGRR 190617 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 217 AM EDT Sun Apr 19 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 /06Z TAFS THROUGH 06Z MONDAY/... Issued at 217 AM EDT Sun Apr 19 2026 VFR is likely much of today with daytime cumulus bases favored to be at or above 4,000 feet. West/Northwest winds will gust during the late morning through afternoon up to about 20-28 knots. Around 18-22 Z, scattered towering cumulus (TCU) may be present near LAN and JXN, possibly growing into cumulonimbus (CB), as there is about a 10-30 percent chance of a thunderstorm in that area and toward the east. Under any TCU or CB may come briefly gustier winds over 30 knots and graupel (small or soft hail, GS). && .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 until 10 AM EDT this morning for MIZ050>052- 056>059-064>067-071>074. Freeze Warning from 11 PM this evening to 11 AM EDT Monday for MIZ050>052-056>059-064>067-071>074. MARINE...Small Craft Advisory until 2 PM EDT this afternoon for LMZ844>849. && $$ DISCUSSION...Thomas AVIATION...CAS MARINE...Thomas HYDROLOGY...Thomas

NWS GRR Office Area Forecast Discussion