textproduct: Chicago

KEY MESSAGES

- Periods of rain/showers will continue through tonight across much of the area, and through Friday night for portions of northwest IN downwind of Lake Michigan.

- Breezy and cooler conditions expected Friday.

- Freezing temperatures likely for much of the area Friday night, and possible again Saturday night and Sunday night in some locations.

- Dry and warmer than average weather early next week.

DISCUSSION

Issued at 248 AM CST Thu Nov 5 2026

00Z upper air analysis and current GOES water vapor imagery depicts an upper level trough across the upper Mississippi Valley and western Great Lakes region. Embedded within the trough was a closed low over northern WI and the UP of MI, as well as a couple of decent vorts (one notably over eastern IA), wrapping cyclonically southeastward through the base of the trough. This pattern will continue to support periods of light rain/showers and drizzle especially north of the I-80 corridor this morning. The main upper trough axis is progged to develop southeastward this afternoon, while surface low pressure currently analyzed over eastern Lake Superior moves east and trails a secondary, fairly-stout cold front across our forecast area this afternoon and evening. An increase in shower coverage is expected as this occurs, along with a shift to blustery northerly winds and colder temperatures behind the front into tonight. The bulk of the rain/showers should gradually end from northwest to southeast across the CWA overnight, though strong cold advection down the fetch of Lake Michigan (H8 temps as low as -4/5C by early Friday) will set up conditions conducive (delta-T 15-19C, ELs near 9 kft) for lake-effect rain showers into northwest IN from later tonight through Friday/Friday night.

Blustery north-northwest winds maintain low-level cold advection across the area Friday, though winds should gradually ease late in the day/evening. Temperatures look to be limited largely to the upper 40s across much of the area, perhaps tagging 50 if clouds break up enough by afternoon over northern IL. Surface high pressure then builds into the region later Friday night into Saturday morning, with clearing skies and diminishing winds expected to allow for freezing overnight lows in the upper 20s/lower 30s across much of the area except the core of the Chicago urban center and northwest IN where clouds/warmer temps are expected downwind of the lake. No frost/freeze headlines are planned, as we're now well past the climatological first freeze date this fall. Dry but cool conditions are expected Saturday with the surface ridge continuing to drift southeast across the area, with highs around 50 and lows again Saturday night around 30 away from the city.

Ensembles are in good agreement in maintaining dry weather from this weekend through early next week, with the jet stream focused just to the north of the region, and an expansive area of surface high pressure from TX to the southern Appalachians/mid-Atlantic region blocking any Gulf moisture return. Models do indicate a Pacific cold frontal passage in the Monday night/early Tuesday timeframe, though with no precipitation forecast. Temperatures are expected to run at or above average (especially daytime temps) with highs in the upper 50s/low 60s (Monday looks warmest ahead of the Pacific front) and lows in the 30s/40s.

Ratzer

AVIATION /06Z TAFS THROUGH 12Z FRIDAY/

Issued at 1145 PM CST Wed Nov 4 2026

Forecast concerns include...

Primarily MVFR CIGs through late Thursday evening. IFR CIGs possible Thursday afternoon/early evening. Periods of drizzle and showers through the period. Wind shift/cold front to northerly Thursday afternoon/evening.

With the exception of brief lower end VFR as of this writing at MDW and GYY, and periods of higher end MVFR overnight, low MVFR CIGs are expected to prevail through Thursday evening. There may be brief periods when there will be high mvfr cigs tonight. IFR CIGs are possible Thursday afternoon into early Thursday evening and trends this evening from guidance suggests IFR CIGs will develop across much of the area Thursday afternoon ahead and behind a cold front and then gradually lift back to MVFR Thursday evening.

While there remains some uncertainty for timing, periods of drizzle and scattered showers will continue through Thursday evening. Showers spreading across the terminals during the early overnight hours paired with drizzle will result in occasional MVFR VSBY. Scattered showers are expected to develop Thursday afternoon as a cold front moves across the area, and these showers could become widespread for at least a few hours until the front moves south of the terminals. Lake effect rain showers may then continue into northwest IN late Thursday night into Friday morning.

Southwest winds will continue through midday Thursday with periodic gusts into the 15-20kt range. Winds will steadily turn to northwest Thursday afternoon then shift northerly with the passage of the cold front. Only medium confidence for specific wind directions, but northerly winds may remain around 360 degrees for at least a few hours before favoring north/northwest later Thursday evening. Gusts into the 20kt range are expected once winds turn northerly. cms/rc

LOT WATCHES/WARNINGS/ADVISORIES

IL...None. IN...None. LM...Small Craft Advisory until 3 PM CST this afternoon for the IL and IN nearshore waters.