


Area Forecast Discussion
Issued by NWS Grand Rapids, MI
Issued by NWS Grand Rapids, MI
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518 FXUS63 KGRR 182327 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI Issued by National Weather Service Green Bay WI 727 PM EDT Wed Jun 18 2025 .KEY MESSAGES... - Severe storms this afternoon/evening - Precipitation chances continue Thursday night into Friday - Hot weather begins Saturday && .DISCUSSION... Issued at 313 PM EDT Wed Jun 18 2025 - Severe storms this afternoon/evening Mesoscale Convective Vortex (MCV) currently crossing central IL is the feature to watch. There is a growing rain shield developing northeast of this low and that is likely more elevated in nature. The MCV is expected to progress into Indiana and we will see a peripheral threat for severe weather across our southern forecast area particularly along the I-94 corridor where all threats are in play, mainly between 4 and 10 PM. There is a short fused hydro threat as well. Impressive rain totals already have been observed across SE Lower MI and there is a Mesoscale Precipitation Discussion (#0478) issued by WPC that discusses the flood threat for southwest Lower MI as well. Please refer to this product for further details. - Precipitation chances continue Thursday night into Friday As noted previously, we can expect wrap around precipitation continuing overnight and at least into the first part of Thursday. Areas south of I-96 could be dry by Thursday afternoon. However, father north more towards US-10, there will be a persistent surface trough juxtaposed with persistent conditional instability and episodic weak upper PV advection in northwest flow. This justifies continued PoPs, primarily north of I-96. - Hot weather begins Saturday Upper ridging becomes especially pronounced by Saturday with attendant mid-level warming/capping. Sunday and Monday will likely feature surface dewpoints in the lower 70s combined with highs in the lower/mid 90s under clear skies. This will yield apparent temperatures in excess of 100 both days. As noted previously, there is a signal for a cold front to ease the situation in the late Tuesday/Wednesday timeframe, but the forcing for this is questionable. Therefore, it`s quite plausible that oppressive conditions will persist into Wednesday and beyond. && .AVIATION /00Z TAFS THROUGH 00Z FRIDAY/... Issued at 726 PM EDT Wed Jun 18 2025 Generally poor flying weather is expected into Thursday morning. An area of low pressure will be moving across southwest Lower Michigan this evening before exiting across the thumb of Michigan late tonight. While the strongest storms will have departed to the east at the start of the taf period, the low pressure system will bring periods of showers, MVFR visibilities at times, and ceilings deteriorating to IFR. Some showers will likely persist into Thursday morning. But flight conditions are expected to gradually improve on Thursday morning before becoming VFR in the 16-19z timeframe. && .MARINE... Issued at 313 PM EDT Wed Jun 18 2025 No headline concerns at this time. A surface low will pass east of the waters, allowing for a brief period of northwest winds tonight. However both the speed and duration will be limited and this will curtail wave growth. The next appreciable chance for marine headlines at this stage looks like Friday night where we will see a response to the effects of persistent southerly flow. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ DISCUSSION...TJT AVIATION...MPC MARINE...TJT