853 FXUS63 KGRR 161206 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 806 AM EDT Thu Apr 16 2026 .KEY MESSAGES... - Lingering Showers and Storm Into Afternoon, Continued Flooding - Dry Friday, Rain and Thunderstorms Friday Night into Saturday - Colder and Windy Sunday - Dry Early Next Week && .DISCUSSION... Issued at 229 AM EDT Thu Apr 16 2026 - Lingering Showers and Storm Into Afternoon, Continued Flooding Thunderstorms have exited the area, leaving areas of rain. Additional storms are noted upstream across southern WI. Although the vast majority of expected precipitation has fallen already, there is a signal in some of the convection allowing models that localized bands of a quick additional half inch or so are possible in some spots before the rain fully exits this afternoon. - Dry Friday, Rain and Thunderstorms Friday Night into Saturday After a dry and warm Friday with highs in the 70s, we will experience deep southwesterly lower tropospheric flow in response to an approaching sharp upper trough. SPC does advertise a Day4 (12Z Sat to 12Z Sun) risk for severe weather that reaches into SE Lower MI, and this is corroborated by several of the medium range AI models. This will depend in large part on frontal timing. Predictability for this might actually be relatively good due to the highly phased and especially prominent nature of the upper trough and associated low level baroclinic zone. - Colder and Windy Sunday Colder air moves in behind the low Saturday with low temperatures Saturday night into Sunday dropping into the upper 20s to 30s. Breezy west to northwest winds will cause wind chills to be in the 20s Sunday morning. Highs are expected to make it into the 40s, but this will still feel quite brisk with the winds and coming off a prolonged period of unseasonable warmth. - Dry Early Next Week Northwesterly flow aloft in the wake of the exiting upper low will yield dry conditions with a gradual warmup. Some of the deterministic model solutions show an upper PV max brushing the northern Great Lakes, but precipitation chances remain in question due to scarcity of low level moisture. The odds currently favor a dry forecast into and including Wednesday, but this could change. The good news is that any precipitation that occurs should be far less impactful than what has been experienced this week. && .AVIATION /12Z TAFS THROUGH 12Z FRIDAY/... Issued at 800 AM EDT Thu Apr 16 2026 Showers and isolated thunderstorms will impact much of West Michigan through early-mid afternoon, as weak low pressure crosses the Great Lakes. This will result in MVFR ceilings/vsbys. Best chances for thunder between roughly 14Z-21Z will most likely be over southern areas... including AZO/BTL/JXN. Winds turn WNW late this afternoon as disturbance passes east and ridge of high pressure builds into the western Great Lakes. Widespread VFR conditions will return by late afternoon and early this evening. Fog development will need to be monitored later tonight. Have introduced IFR vsbys /2-3 SM/ after 05-06Z at all TAF sites, given clear to partly cloudy skies, moist boundary layer, light winds, and good radiational cooling. Given set up and upstream conditions this morning, vsbys could ultimately be much lower. && .MARINE... Issued at 229 AM EDT Thu Apr 16 2026 In coordination with MKX, have extended the Marine Dense Fog Advisory until Friday morning. As noted previously, we expect increasing winds and waves to become hazardous to small craft beginning Friday night. && .HYDROLOGY... Issued at 250 PM EDT Wed Apr 15 2026 Bottom line: The most significant flood in recent years continues to develop along the Muskegon River. Meanwhile, heavy rains last night are also likely now going to create another round of primarily minor flooding along the Grand River and associated tributaries. Another 1.5 to 2.5 inches of rain fell last night across a large portion of the area, with the exception of the headwaters areas of the Grand, Muskegon, and Kalamazoo watersheds (where closer to 1 inch of rain fell). Unfortunately, another 0.5 inches is expected tonight and tomorrow across a large area, with localized streaks of 1 to 3 inches. Along with the river flooding, urban and low lying areas will be prone to flooding due to any additional thunderstorms rains in the next day or so. Further south, the Kalamazoo River has been a bit drier lately, so no flooding is expected to develop there, though urban and poor- drainage area flooding will definitely be possible into Thursday as additional rounds of thunderstorms move through. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Flood Watch through late tonight for MIZ037>040-043>046-050>052- 056>059-064>067-071>074. MARINE...Dense Fog Advisory until 8 AM EDT Friday for LMZ845>849. && $$ DISCUSSION...TJT AVIATION...Smith MARINE...TJT HYDROLOGY...AMD

NWS GRR Office Area Forecast Discussion