textproduct: Chicago

KEY MESSAGES

- Near to above normal temperatures with predominantly dry conditions are expected to continue through much of this week.

DISCUSSION

Issued at 259 PM CDT Tue Oct 6 2026

A cold front will drop through the area from northwest to southeast early tomorrow. The 12Z runs of the moist-biased NAM, NAM Nest, and NSSL-WRF all try to spit out some rain in our area as the front and an associated shortwave roll through tomorrow morning. However, the lack of more appreciable mid-upper-level cloud cover or any real signs of virga over North Dakota at this hour suggest that these models are overestimating the strength of this shortwave and the amount of moisture associated with it. The model guidance that has a better handle of what's currently going on over North Dakota maintains precipitation-free conditions along the front as it tracks through our forecast area, so a dry frontal passage is still expected tomorrow. While modest cold air advection will occur off of northwesterly winds behind the front, relatively deep post-frontal mixing and mostly sunny skies should nevertheless support high temperatures tomorrow that will be near or slightly higher than today's highs in the mid 70s to low 80s (warmest in our southern counties).

Cooler high temperatures in the mid 60s to mid 70s are ultimately expected on Thursday amidst dry conditions as modest northwesterly to northerly winds persist and the heart of the cooler air mass and an attendant surface high settle into the region. Similar to slightly warmer temperature readings are then favored again during the daytime on Friday as southerly return flow becomes established over the region. There remains a signal in ensemble guidance for warm air advection/isentropic ascent to induce some showers or sprinkles in the region on Friday as mid-level lapse rates steepen modestly. However, there is still not much consistency with where this precipitation may occur, and dry low-mid air is also a factor that precludes higher confidence in the occurrence of measurable rainfall here on Friday. The latest NBM's mentionable PoPs remain displaced just to our north and northwest, and this still looks reasonable for now.

Persisting warm air advection off of southerly winds will lead to warmer temperatures on Saturday, with low-mid 80s high temperatures looking likely across a good chunk of our forecast area amidst sunny or mostly sunny skies. The forecast for Sunday remains more up in the air, in large part due to considerable uncertainties over how a tropical disturbance (invest 92L) in the Gulf will evolve in the coming days. Broadly speaking, this disturbance is expected to become an organized tropical system before making landfall along the Gulf Coast and encountering a broad upper-level trough. Its remnants and the associated tropical moisture will initially surge northward before turning northeastward towards the Mid-Atlantic/New England. How quickly this northeastward turn occurs will dictate whether any associated rain gets into our forecast area, which, in turn, will also have an influence on temperatures for Sunday. While most Grand Ensemble members still favor this activity remaining to our southeast, ensemble support for a solution where rain gets into at least our southeastern counties has steadily increased over the past few model cycles. The latest NBM came in with chance PoPs across our southeastern CWA as a result, but if this northwestward trend continues to garner more support, then these PoPs may need to be increased and/or expanded further.

Ogorek

AVIATION /00Z TAFS THROUGH 06Z THURSDAY/

Issued at 601 PM CDT Tue Oct 6 2026

Southwesterly gusts will subside within the next hour as surface decoupling commences. A 35-40kt southwesterly low-level jet may lead to marginal LLWS criteria overnight (particularly at RFD/DPA), but will withhold mention in the TAFs given an expectation for surface wind magnitudes to remain in the 8 to 12kt range. Skies should be largely clear overnight, though cannot rule out a few scattered cumulus clouds based near 5000 or 6000 feet within the low-level WAA regime.

A dry cold front will move across the terminals after daybreak shifting winds to northwesterly. Pressure rises in the wake of the front will be fairly modest (only 1 to 2 mb over 6 hours), so will keep wind magnitudes close to 10 kt behind the front. With that said, do see a signal for a lake boundary to stall just west of GYY leading to northeasterly winds by early afternoon. A few high clouds should stream overhead toward the end of the TAF period.

Borchardt

LOT WATCHES/WARNINGS/ADVISORIES

IL...None. IN...None. LM...Small Craft Advisory until 7 PM CDT this evening for the IL nearshore waters.