textproduct: Chicago

KEY MESSAGES

- Dry conditions and warmer temperatures continue through Tuesday.

- Precipitation chances and cooler temperatures return mid to late week, including periods of lake effect showers.

DISCUSSION

Issued at 252 AM CST Mon Nov 9 2026

Light winds and mostly clear skies will lead to another frosty start to the day, particularly in the outer suburbs and rural areas. Today will be similar to yesterday, albeit less breezy, with high temperatures in the upper 50s to lower 60s and occasional thin high-clouds moving through. A weak cold front will drift across the area late tonight, though a lack of notable airmass differences behind the front should allow temperatures to still warm into the upper 50s to mid 60s on Tuesday.

A pattern shift toward cooler temperatures and renewed precipitation chances is still anticipated mid to late week. This begins with a compact shortwave that is forecast to move across the region on Wednesday, bringing our next chance of showers (30-50% chance). There remains some uncertainty in where the associated surface low tracks, which will then factor into the location of greatest shower coverage. At this distance, locally higher chances exist near and south of I-80. While low to mid-level lapse rates this far north are not especially steep, any deeper convection may be able to tap into sufficient elevated instability to produce a few lightning strikes or small hail. Currently hold off on a formal mention in the gridded forecast, with the slightly better potential existing in central Illinois.

The aforementioned shortwave may phase with a series of vorts rounding a closed upper low over Ontario as the broader upper trough descends across the eastern CONUS. One such vort may dive across the area on Thursday, which could bring showers (and perhaps a few wet snowflakes) well inland. The resultant colder airmass advecting across a still warm Lake Michigan will set the stage for a multi-day period of lake effect showers into portions of the area. While there remains strong ensemble support for lake effect precipitation, uncertainty remains regarding the resultant low-level flow orientation (NNE vs NNW/NW), which will determine if and how often the band(s) of showers drifts west into northeast Illinois or it if remains largely over northwest Indiana. These details are difficult to pin down this far out and will continue to monitor trends over the next few days. While some models are already producing minor snow accumulations, model soundings still show cloud tops remaining just below the DGZ, which paired with the warm ground temperatures would likely limit or even prevent snow accumulations. Nevertheless, it continues to look like snow will likely mix in with the lake effect showers at times.

A strong surface high expands eastward over the weekend into next week, bringing an end to lake effect showers and leading to another stretch of dry conditions with temperatures gradually moderating back into the 50s.

Petr

AVIATION /18Z TAFS THROUGH 00Z WEDNESDAY/

Issued at 1128 AM CST Mon Nov 9 2026

Maintained no significant aviation forecast concerns for this taf period.

Within this period of mid level ridging, a wave passes to the north of the area. This provides times of scattered to few high clouds in the first 6-12 hrs of the period before they vacate the area. Additionally, the gradient increases enough that a period of marginal LLWS is possible with some low level turning of winds. Given 30-35 kts around 500 m between 1 and 7z and winds staying above 5 kts overnight, am still not ready to put in a LLWS group yet, but future shifts will want to interrogate this aspect of the forecast further because it's close.

The lean is towards VFR for this forecast period. There were a few sites that saw some patchy morning fog this morning, but with winds remaining excited above 5 or 6 kts overnight, the expectation is that fog would be, at most, patchy/shallow enough to remain out of tafs for Tuesday morning. Cross-over temps are not conducive, but that would make sense in the WAA pattern with the wave passing by.

Roller/NWSIWX

LOT WATCHES/WARNINGS/ADVISORIES

IL...None. IN...None. LM...None.