FXUS63 KIWX 170417 AFDIWX Area Forecast Discussion National Weather Service Northern Indiana 1217 AM EDT Sat Oct 17 2026 .KEY MESSAGES... - Patchy frost expected tonight for south central Lower Michigan into portions of northern Indiana. See the frost advisory for details. - Widespread frost is expected Saturday night into Sunday morning with a potential of temperatures dropping to the freezing mark, especially east of Interstate 69. - After the below normal temperatures this weekend, temperatures rebound back above normal for much of next work week with dry weather expected. && .DISCUSSION... Issued at 324 PM EDT Fri Oct 16 2026 Showers associated with some strong low/mid level frontogenesis forcing will continue to exit northwest Ohio the remainder afternoon. The primary focus for additional rainfall will remain back across northwest Indiana and southwest Lower Michigan where secondary surface trough associated with strong positively tilted upper trough is augmenting lake effect rain showers. The focus for these lake effect/enhanced rain showers will shift to northwest Indiana this evening as low level winds veer northerly behind the secondary sfc trough. A Wind Advisory remains in effect through this evening for LaPorte and Berrien Counties, although the window for 35 mph plus gusts may be confined to a 20 to 23Z timeframe. Boundary layer mixing may be tempered a bit by the very moist profiles in place, and thus confidence is beginning to diminish somewhat in realizing advisory level winds, particularly after 00Z as a lake-induced thermal trough is likely to sharpen and weaken the low level height gradient. At this time will continue the Wind Advisory and will defer to next shift to monitor for possible cancellation depending on how trends evolve. Lake effect rain showers may persist into the early overnight hours across northwest Indiana as thermal troughing response over southern Lake Michigan matures this evening. The positively tilted nature of the upper trough should allow for synoptic scale mid level subsidence to build in quickly later this evening and overnight resulting in expected diminishing cloud trend outside of lingering lake effect. Low levels should remain well mixed into the early evening hours with some better potential of decoupling overnight. This introduces the risk of some patchy frost development and temperatures dropping into the low-mid 30s tonight. The best chance of frost formation still appears to be across much of southern Lower Michigan into portions of north central Indiana situated between more delayed cloud cover decrease in the west with lake effect, and slightly better mixing persisting east of I-69 into the overnight. Quiet weather is expected on Sunday as the southern Great Lakes and Ohio Valley will be positioned downstream of broad longwave ridge axis across central CONUS allowing for extended synoptic scale subsidence. Sfc anticyclone will overspread the region late Saturday afternoon into Saturday evening with some lighter southwest return flow setting up across the western Great Lakes by Sunday morning. Frost/freeze potential will need to be considered again for this period. Some minor modification of low level thermal trough is expected Saturday but mainly clear skies and light winds should allow for good radiational cooling Saturday night and a potential of temperatures dropping to the freezing mark. Best chances based on timing of the high pressure still appear to be east of I-69 where a Freeze Watch has been issued. Some combination of Frost Advisories and/or Freeze Warnings will likely be needed Saturday night. Upper flow pattern will become more stagnant and blocked in nature for much of next week with little overall progression in mean positioning of central CONUS ridge. Gradual day to day moderation and max temperatures in upper 60s to lower 70s and dry conditions will prevail for much of next week. Cannot completely rule out some patchy frost concerns Sunday and Monday nights, but this is a low confidence item at this time. && .AVIATION /06Z TAFS THROUGH 06Z SUNDAY/... Issued at 1217 AM EDT Sat Oct 17 2026 Northerly winds gusting to around 20 knots will diminish to less than 10 knots by daybreak as high pressure builds in. VFR with light winds and little in the way of cloud cover otherwise this weekend into much of next week. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...Frost Advisory from 4 AM to 9 AM EDT this morning for INZ005>009-014-017-104-116-204-216. Freeze Watch from late tonight through Sunday morning for INZ006>009-017-018-023>027-032>034-116-216. OH...Freeze Watch from late tonight through Sunday morning for OHZ001-002-004-005-015-016-024-025. MI...Frost Advisory from 4 AM to 9 AM EDT this morning for MIZ078>081. MARINE...Gale Warning until 2 AM EDT early this morning for LMZ043-046. Small Craft Advisory until 11 AM EDT Sunday for LMZ043-046. && $$ DISCUSSION...Marsili AVIATION...Steinwedel