513 FXUS63 KIWX 181807 AFDIWXArea Forecast Discussion National Weather Service Northern Indiana 207 PM EDT Thu Sep 18 2025
.KEY MESSAGES...
- Remaining warm through the weekend with above normal high temperatures in the 80s.
- Chances of rain return for the weekend, especially later Sunday into Sunday night (50-60%).
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.DISCUSSION... Issued at 207 PM EDT Thu Sep 18 2025
More of the same into tonight and Friday as upper level ridging lingers between a low pressure center over the North-central US and an upper trough over southeast Canada. A backdoor cool front associated with the southeast Canada trough drops into northern zones tonight into Friday morning with the only potential impact being patchy fog early Friday in its wake thanks to some marine influence from Lake Huron/Erie.
Weak height falls overspread the region Friday night into this weekend as the Plains low/upper trough evolves east toward the MS River Valley and western Great Lakes. This will bring initial low (20-30%) chances for a few showers into mainly western IN and southwest MI Friday night into Saturday as a weak shortwave and elevated warm front lift through. Most of the area will remain dry however with more clouds around and temps still above normal for late Sept.
Late Sunday into Sunday night still appears to be the best opportunity (50-60%) for greater rain shower coverage and perhaps a few embedded storms as a more pronounced shortwave and surge of deeper moisture track east-northeast through the western/lower Great Lakes. Predictability then falls off into next week as the broad upstream trough eventually cuts off under building south-central Canada heights. Opted to hold with NBM daily broadbrush PoPs as a result (mainly 20-50%) through at least the mid-week periods given expectations for moist low levels with a front and this meandering upper low nearby. High temperatures will be a bit cooler in this regime (near normal), though humidity levels will be more elevated.
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.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/... Issued at 1216 PM EDT Thu Sep 18 2025
High pressure will continue to keep any flight impacts well west of the area into at least early Saturday. Chances for shallow fog appear to be less than past nights, so no mention in TAFs.
Models show winds remaining AOB 5 kts varying from S to NE over the next 12 to 18 hours. Have opted to go with a variable direction for now, but a steadying of the direction should occur by Fri morning from the E or NE.
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.IWX WATCHES/WARNINGS/ADVISORIES... IN...None. OH...None. MI...None. MARINE...None.
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DISCUSSION...Steinwedel AVIATION...Fisher
NWS IWX Office Area Forecast Discussion