080 FXUS63 KIWX 131843 AFDIWXArea Forecast Discussion National Weather Service Northern Indiana 243 PM EDT Sat Sep 13 2025
.KEY MESSAGES...
- Scattered showers and storms are possible this evening and early overnight along and south of US 30. Storms will be capable of producing small hail and gusty winds.
- A persistent dry and warm pattern sets up starting on Sunday and lasting through next week. Expect highs in the upper 80s to low 90s each day.
- Minimum relative humidities as low as 30% to 40% next week may be conducive for elevated fire danger.
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.DISCUSSION... Issued at 242 PM EDT Sat Sep 13 2025
In the wake of the widespread, steady rain that moved through earlier today, scattered showers and storms are possible this evening and early overnight. Development is already occurring southeast of Chicago in northwest Indiana. Showers and storms will move southeast this evening along a remnant boundary, with gusty winds, small hail, and heavy rain. SPC has maintained the Marginal severe risk for today although the threat appears isolated. Mid level lapse rates are decent but the better instability gradient is to our west. The best chances for any additional rain or storms today will be along and south of the US 30 corridor. Overnight, expect skies to gradually clear and showers to diminish. With lingering ground moisture, light winds, and clearing skies, areas of patchy fog may develop early Sunday morning.
For Sunday and into early next week, an Omega Block pattern sets up. An upper level ridge axis will build over the Midwest and Great Lakes regions, allowing for warmer temperatures and persistent dry conditions. Highs will be in the upper 80s to near 90 degrees each day from Sunday through the middle of next week. The humidity will be noticeable with dewpoints in the mid 60s. While not uncommon this late in the summer, the heat will also allow for large diurnal temperature swings as dry conditions persist through the week. In fact, given that we have been lacking significant rainfall since mid August, drought is likely to persist and/or develop in the coming weeks.
By Friday and into next week, a return to seasonable temperatures appears possible. Long range guidance hints at a pattern change coming around this time next week. The upper level ridge pattern breaking down and allowing for a cold front to sweep through sometime between Friday and next Sunday, which would usher in a cooler Canadian airmass and opportunities for rain.
One additional concern for next week given the above normal temperatures and dry conditions is fire danger. Sunny skies and persistent warmth should allow for minimum afternoon relative humidity values to drop between 30 to 40 percent. However, should any grass or brush fires develop, winds should be light enough that it likely won`t spread quickly. Avoid outdoor burning!
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.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/... Issued at 123 PM EDT Sat Sep 13 2025
Primary area of rain associated with passing shortwave has dissipated and exited the terminals. However, marginal moisture and instability in a region of weak isentropic upglide will continue to support SCT showers through the afternoon. MUCAPE appears too limited to warrant a thunder mention but it can`t be entirely ruled out, especially at KSBN. Dry/quiet weather returns overnight with just some high-based cu expected through Sunday.
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.IWX WATCHES/WARNINGS/ADVISORIES... IN...None. OH...None. MI...None. MARINE...None.
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DISCUSSION...Johnson AVIATION...AGD
NWS IWX Office Area Forecast Discussion