469 FXUS63 KIWX 201821 AFDIWX Area Forecast Discussion National Weather Service Northern Indiana 221 PM EDT Mon Oct 20 2025 .KEY MESSAGES... - Scattered showers likely overnight, especially between 1 AM to 7 AM EDT Tuesday. A lull in rain showers is expected Tuesday between sunrise and midday. - Lake enhanced rain showers increase in coverage Tuesday afternoon and evening, persisting off and on (especially north of US 30) through Thursday morning. - West/northwest winds could gust as high as 30 to 35 mph on Tuesday and Wednesday. - Below normal temperatures persist through the week ahead. Highs Wednesday and Thursday struggle to get out of the low 50s. - Patchy frost possible Wednesday night and a widespread freeze is possible Thursday night. && .DISCUSSION... Issued at 219 PM EDT Mon Oct 20 2025 Another potent system will impact the area over the next several days. An area of surface low pressure is currently located over western Minnesota with a trailing cold front extending south across Iowa, Nebraska, and into central Kansas. As this low lifts north across the Upper Midwest tonight, clouds and showers will advect into our area ahead of the cold front. The best chances for rain will be between 1 AM to 7 AM EDT Tuesday, with most locations getting in on a few hours of scattered light to moderate showers. The cold front quickly exits to the east and our area will be in the dry slot of the low pressure system by sunrise. A break in the rain will last through midday before increased upper level support will allow for lake enhanced rain showers to increase in coverage by the afternoon. A closed upper level low will develop over the Upper Great Lakes region on Tuesday with positive 500mb vorticity advection as well and a notable 250mb jet streak rounding out the base of a strong upper level trough. As the surface low spins and strengthens over northern Lower Michigan, this system will stick around for much of the midweek. Persistent CAA and northwest, cyclonic flow at the synoptic level will allow for diurnally driven periods of off and on lake enhanced showers Tuesday and again on Wednesday (especially north of US 30). It will be breezy too with a tightening pressure gradient due to the deepening surface low. West/northwest winds will be gusting as high as 30 to 35 mph at times Tuesday and Wednesday. It will finally feel like fall this week with below normal temperatures through much of the upcoming week. The aforementioned midweek system and gusty winds will allow for cooler temperatures to prevail across the Great Lakes region. Wednesday and Thursday will be the coolest days of the week with highs struggling to make it out of the low to mid 50s. As cooler air filters in midweek, patchy frost may develop Wednesday night, especially away from Lake Michigan. High pressure builds in on Thursday and the coldest air of the season so far arrives with potential for a widespread freeze Thursday night. Lows will likely be in the low to mid 30s area-wide Thursday night into Friday morning. The growing season ended on October 15th in Lower Michigan but should frost/freeze headlines be warranted, they will still be issued across Northern Indiana and northwest Ohio (where the growing season persists until November 1st or until the first freeze, whichever is first). Low chances for rain exists over the weekend but dry weather returns early next week as an upper level ridge builds across the central CONUS. Temperatures will continue to be below normal to perhaps near normal into early next week. No major warm up is in sight as we enter the last full week of October. && .AVIATION /18Z TAFS THROUGH 18Z TUESDAY/... Issued at 1223 PM EDT Mon Oct 20 2025 VFR conditions expected through the TAF cycle. Clear skies and southerly winds near 10 knots will remain the story this afternoon before a cold front swings through later tonight with showers and lower VFR cigs accompanying it. A strengthening low level jet will lead the front later this evening into the early overnight with a period of LLWS possible at each terminal. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...None. OH...None. MI...None. MARINE...Small Craft Advisory until 4 PM EDT Tuesday for LMZ043-046. && $$ DISCUSSION...Johnson AVIATION...Steinwedel