886 FXUS63 KIWX 292246 AFDIWXArea Forecast Discussion National Weather Service Northern Indiana 646 PM EDT Mon Sep 29 2025
.KEY MESSAGES...
- Much above normal temperatures to continue on Tuesday 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 219 PM EDT Mon Sep 29 2025
Very few changes made to the previous forecast with an extended period of above normal temperatures and dry conditions expected. An omega-block pattern continues across the central CONUS with little movement in the upper ridge axis position expected through the middle of the week. Some slight change in the orientation of the upper ridge axis is expected later Tuesday into Wednesday as several short waves top the ridge across south central Canada while at the same time a stronger upper vort max digs southeast across southeast Canada. This evolution will allow for some backdoor cool advection via some strengthening of the east-northeast low level flow. Slightly cooler low level thermal profiles should shave a few degrees off high temperatures over the next few days, especially by Wednesday and Thursday as some increase in high level cloudiness is also expected with some elevated moisture spilling over the ridge.
A cut-off upper level vort max across the southern Plains today will gradually get ingested into Corn Belt later Tuesday night and will eventually shear across western/southern Great Lakes late Thursday into Friday. Some weak 850 mb moisture return should precede this dampening wave, but any low probability of an isolated shower should remain well west/southwest of the local area late this work week.
By Friday night, low level ridge axis should make enough eastward progress to allow a south/southwest low level flow regime to set up for the weekend. These south/southwest winds will result in some weak low level warm advection and moderation of highs back into the lower to middle 80s for the weekend. However, low level flow trajectories will not be supportive of significant moisture transport as far north as the southern Great Lakes region. Some indications in medium range guidance persist regarding a lead short wave lifting across the Upper Midwest Saturday night, but given lack of moisture return and possibility that western periphery of the low level anticyclone may maintain influence across the local area, no mentionable PoPs are included over the weekend. There has been a dprog/DT trend of a less phased northern/southern stream heading into early next week resulting in more of a cut-off negative upper height anomaly across western CONUS and less southward penetration of a low level baroclinic zone with the northern stream trough. Given large amounts of background anticyclonic shear across the northern tier of CONUS, this idea of less phased, positively tilted systems seems to make sense and thus will hold off of any mentionable PoPs through the remainder of the long term period with continued above normal temperatures.
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.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/... Issued at 641 PM EDT Mon Sep 29 2025
High pressure over the Great Lakes will provide another round of tranquil TAFs. Look for northeast wind to decrease with sunset and increase once more in the afternoon. Cannot rule out patchy ground fog near sunrise Tuesday morning, primarily at KFWA, closer to the eastern Great Lakes marine influence. However, forecast soundings are rather dry overall. Will pass this concern on to the next shift for further consideration.
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.IWX WATCHES/WARNINGS/ADVISORIES... IN...None. OH...None. MI...None. MARINE...None.
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DISCUSSION...Marsili AVIATION...Brown
NWS IWX Office Area Forecast Discussion