185 FXUS63 KIWX 301827 AFDIWXArea Forecast Discussion National Weather Service Northern Indiana 227 PM EDT Tue Sep 30 2025
.KEY MESSAGES...
- Much above normal temperatures to continue today with highs in the low to mid 80s.
- Cooling slightly for Wednesday and Thursday but high temperatures are expected back into the lower to middle 80s for Friday into the weekend.
- Dry weather continues through the remainder of the week.
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.DISCUSSION... Issued at 234 AM EDT Tue Sep 30 2025
Mid level ridging overhead offsets uplift southeast of the US and this suppression of rain-producing systems as a result of the ridging and antecedent dry air continues into early next week.
Riding over the top of this stalled ridging is a surface high pressure system that ends up in southeast Canada and the northeastern US today and Wednesday. The main change that will result from a backdoor cold front that arrives Wednesday and Thursday will be dry air as dew points in the 40s will become more possible and widespread, especially on Thursday. Meanwhile, temperatures will slowly stair step down from our mid to upper 80 degree highs, experienced Saturday through Monday, to more 70 degree highs Wednesday and Thursday. Widespread 30 percent MinRH values and varying amounts of 20 percent MinRH values will be present from Tuesday through Thursday. The good thing is a majority of our winds are expected to be light enough to restrict the spread of grass fires. The one exception might be Wednesday when 15 to 25 mph gusts are possible mainly along and north of US-30. Now, sometimes with these fronts, we end up with sprinkles as low to mid level moisture is able to fall and evaporates in a dry boundary layer. It appears that, while some clouds will be around, not enough moisture will be around to create rainfall.
A trough resides on the west coast of the CONUS and normally this would be enough to get Gulf moisture and get a rain chance into the area. However, the mid level ridging, antecedent dry air and the tendency for the vorticity to shear out and weaken as it traverses northward to west of the area will allow the rain chances to evaporate before they arrive here. Finally, better Gulf moisture arrives on the backside of a ridge in the southeastern US between Monday and Tuesday of next week in advance of a cold front. This pattern is usually conducive to rain, but we`ll need to see if the 60 degree dew points can, in fact, make up this way and overcome the antecedent dry air.
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.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/... Issued at 159 PM EDT Tue Sep 30 2025
VFR vsbys and cigs look to continue and prevail through the remainder of this TAF forecast. High clouds will increase slightly through the period. Some patchy ground fog will be possible for mainly far eastern sections of the forecast area but have opted to keep mention out for the TAF sites as ground fog should remain outside of the TAF locations, especially KSBN. Light northeasterly winds expected outside of a few periods of of gusty northwest winds with gusts up to around 20 kts for KFWA this afternoon through 12z Wed and again tomorrow after 17z Wed.
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.IWX WATCHES/WARNINGS/ADVISORIES... IN...None. OH...None. MI...None. MARINE...None.
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DISCUSSION...Roller AVIATION...Andersen
NWS IWX Office Area Forecast Discussion