252 FXUS63 KGRR 151845 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 245 PM EDT Thu Oct 15 2026 .KEY MESSAGES... - Fall Storm System to bring Wind, Rain and Lightning to the area - Rather benign weather expected this weekend into early next week && .DISCUSSION... Issued at 245 PM EDT Thu Oct 15 2026 - Fall Storm System to bring Wind, Rain and Lightning to the area Low pressure is centered just east of Des Moines Iowa at 18Z with widespread rain located to the north of the low over Minnesota and Wisconsin. Two upper shortwaves from both the northern stream and southern stream are phasing off to the west over the upper midwest at this time. As such, the low will deepen as it moves east through the Lower Peninsula. Widespread/deep lift will sweep through Southwest Lower Michigan between roughly 400pm this afternoon and 400am tonight. The bulk of the rain will fall during this period. The lift is driven by the right entrance region of an upper jet that will be located overhead which will drive a low level response of strong isentropic lift and significant moisture transport. Sounding climatology for DTX shows the max PWATs for today being 1.55 inches. We will be north of 1.75 inches this evening. Given abnormal moisture in the depth of the column tonight we expect efficient rainfall production. Most areas will see 0.50 to 1.00 amounts. Amounts may exceed an inch up towards Ludington. Given low river levels and amounts that are not overly concerning not expecting flooding issues. Thunderstorms are a possibility this evening, especially along I-94 between 800pm and 200am. The instability is not strong, several hundred j/kg, but given the dynamics, thunder is a distinct possibility. Wind is the next concern and we have Gale Warnings out on the big lake. As for the land, we feel we will stay just below wind advisory criteria with most gusts in the 30-40 mph range. It will very much feel like fall with a wet, windy and rainy system working through the state. The second portion of the event will come on Friday as a strong cold front sweeps south around daybreak. Showers will accompany the front and usher in cold enough air for lake effect rain. Midday into the afternoon CAPE over the lake is maximized, pushing towards 1,000 j/kg. We are likely looking at thunderstorms off the lake given the significant moisture boost this time of the year via the warmer water. Some diurnally driven showers and storms will be possible inland as well given the cold air aloft. The most concentrated rain will be working down the length of the lake though in northerly flow. - Rather benign weather expected this weekend into early next week Quiet weather conditions will persist over the weekend into early next week as high pressure dominates the scene both at the surface and aloft. The main item of note is that frost and freezing temperatures are possible both Friday night and Saturday night. && .AVIATION /18Z TAFS THROUGH 18Z FRIDAY/... Issued at 117 PM EDT Thu Oct 15 2026 No significant changes to the forecast other than adding detail to the first few hours and some time adjustments. Conditions will deteriorate over the next several hours to IFR and LIFR as showers and low clouds move in. A brief window of little showers and MVFR cigs is likely from 05z-08z before lake effect rain showers keep MVFR conditions in play, potentially IFR in heavier showers, continuing through the rest of the TAF period. A window of LLWS is expected for a few hours tonight as winds shift to westerly aloft, before increased gusts to 25-30 knots develop. && .MARINE... Issued at 245 PM EDT Thu Oct 15 2026 A deepening fall storm system is still expected to pass through the Great Lakes in the next 24-36 hours. The low will reach 995mb to 999mb Friday morning and early afternoon as it passes east from Ontario into Quebec. To the west a stout high pressure will be sliding south through the plains at a magnitude of 1040+ mb. Even though the distance between these two features is fairly wide, a tightening pressure gradient will reach its peak on Friday. The strongest winds will likely occur from midday into the evening hours with Gales likely along with the possibility of some Storm Force gusts. 40-45 knot gales look very reasonable over the water. Given the flow is north or even just east of north, the largest waves will be out over the open waters. That said, we are looking at 8 to 13 footers in the nearshore waters. Given along shore flow and water levels (near 579ft) that are 2.5 feet below advisory (582.5ft) we are not expecting any lakeshore flood issues in our area. Small Craft Advisory begins this evening and lasts into Friday morning. A Gale Warning is in place from Friday morning into Friday night. Two items we will be watching are... 1) do we need to jump into the Gale earlier as some models are showing gales in the 06Z-12Z time frame tonight and 2) how much will the wind touch storm force tomorrow. Do not see either as a high probability at this point and will leave the headlines unchanged. Waterspouts will be possible over the lake late tonight and Friday morning before the wind truly ramps up. The stronger winds tends to shear apart waterspouts. Much of this activity will remain over the lake given northerly flow. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...Small Craft Advisory from 11 PM this evening to 11 AM EDT Friday for LMZ844>849. Gale Warning from 11 AM Friday to 2 AM EDT Saturday for LMZ844>849. && $$ DISCUSSION...Duke AVIATION...Thomas MARINE...Duke

NWS GRR Office Area Forecast Discussion