307 FXUS63 KIWX 272243 AFDIWXArea Forecast Discussion National Weather Service Northern Indiana 643 PM EDT Sat Sep 27 2025
.KEY MESSAGES...
- Dry and partly to mostly sunny through next week.
- Highs will be in the low to mid 80s through Tuesday cooling into the 70s for the middle and latter portions of the work week.
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.DISCUSSION... Issued at 215 PM EDT Sat Sep 27 2025
A quiet weather pattern to be maintained through this forecast valid period with seasonably warm and dry conditions persisting.
Primary short wave track tonight into Sunday will be across south central Canada as an upper level wave moves into western Quebec by daybreak Sunday. A weak frontal zone will drop across the southern Great Lakes in response to this feature Sunday morning. Light onshore winds are expected to develop across far NW IN/SW Lower Michigan early Sunday morning which could promote some patchy fog formation across the extreme northwest. Otherwise, clear skies and light winds will promote another night of good radiational cooling conditions and lows in the mid 50s.
Mid/upper level height rises will commence once again Sunday morning with the departure of the northern Great Lakes/south central Canadian negative upper height anomaly as a 590 dm ridge builds across the MS Rvr Valley. Mid level subsidence and very weak westerly low level WAA in wake of morning short wave should allow for highs a few degrees higher on Sunday into the middle 80s for many locations.
Little change in the day to day weather expected through midweek as an omega block-like pattern develops. This stable wave pattern/blocking should keep the upper ridge axis parked from the southern Great Lakes into southwest Ontario. This pattern should produce comparable highs in the mid 80s again on Monday with a possibility of a few slightly warmer readings given potential of superadiabatic lapse rates with continued dry soils.
For Tuesday into Thursday, guidance has been consistent in a more substantial upper trough dropping southeast across SE Canada with some backdoor-like cold advection building westward across the eastern Great Lakes. Some of this cooler low level air should advect westward in easterly low level flow regime for the end of the work week with highs back into the mid 70s by Thursday.
The stagnant upper level pattern does still appear to break down some by next weekend. Medium range deterministic/ensemble guidance suggests a lead short wave should try to dampen central CONUS upper ridging for first part of next weekend. This weakened upper ridging could then be more conducive for better southward latitudinal progression of next upper trough axis in the Day 8-10 period. This would increase chances of more substantial cool front, but not until well after this forecast valid period. Dry conditions were maintained through this forecast as any moisture transport of note ahead of the lead wave for Saturday will be hard to come by given expansive southeast anticyclone at this time.
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.AVIATION /00Z TAFS THROUGH 00Z MONDAY/... Issued at 640 PM EDT Sat Sep 27 2025
The TAF conditions including weak flow, stable conditions, dry air and few clouds will greatly favor VFR TAFs.
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.IWX WATCHES/WARNINGS/ADVISORIES... IN...None. OH...None. MI...None. MARINE...None.
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DISCUSSION...Marsili AVIATION...Skipper
NWS IWX Office Area Forecast Discussion