textproduct: Chicago

KEY MESSAGES

- Mild temperatures (highs in the 50s) are expected Sunday through Tuesday.

- Widespread rain (>80% chance) returns areawide late Monday into early Tuesday.

- Turning cold and blustery Wednesday with wind gusts > 35 mph, potentially paired with a few flurries.

- Unseasonably cold temperatures (highs in the 30s) continue on Thanksgiving and through the end of the week.

DISCUSSION

Issued at 245 PM CST Sat Nov 22 2025

A thin layer of alto-stratus clouds has put a several hour damper on today's sunshine, particularly across northern Illinois, though there may be a few breaks in the clouds prior to sunset as the back edge continues to shift southeast across the area. This has also slowed some of our diurnal warming this afternoon, with temperatures in cloudier areas remaining mainly in the mid-upper 40s. However, continued southwesterly low- level warm advection should still allow temperatures to reach the lower 50s across the far southern CWA into central Illinois. A dry cold front is then slated to move across the area this evening and overnight but is not expected to result in much more than than a west northwest wind shift paired with another period of increased cloud coverage.

Sunday continues to look more solidly mild for mid-to-late November standards, with forecast highs in the lower 50s areawide. A deeper subsidence layer in the wake of tonight's cold frontal passage should also help limit cloud coverage compared to what occurred today.

A cut-off low currently centered over Baja California is forecast to lift northeast toward the region early next week as it attempts to merge back into the broader upper-level flow. This will be the primary driver of an expected round of widespread precipitation Monday night into Tuesday (>80% chance). Warm temperatures in the upper 40s to upper 50s will support rain being the only precipitation type with this system with forecast precipitation amounts generally around 0.15-0.45".

A vigorous shortwave then dives across the northern Plains in the wake of the early week system, with an associated strong cold front forecast to move across the area Wednesday morning. This will usher in the much anticipated unseasonably cold airmass (-10 to -15C 850 mb temps!) across the region for the Thanksgiving holiday period. The primary impacts for Wednesday in addition to falling temperatures will be the winds. While still several days out, it does appear that wind gusts could exceed 35-40 mph for a time which would also result in wind chills dropping into the 20s. While the better signal remains largely north of the IL-WI state line, a few flurries and/or brief snow showers could round the system during the day on Wednesday and lead to localized visibility reductions (15% chance).

With the cold airmass still in place, forecast highs both Thanksgiving and Friday are only in low to mid 30s with overnight lows in 20s. Other than potential lingering lake effect snow showers in far northeast Porter County, dry conditions are expected.

After a brief break, ensemble guidance continues to favor the pattern turning more active once again toward the end of the week into the first week of December, with upper troughing setting up across the western CONUS and upper ridging across the eastern CONUS. If this occurs, the resultant southwesterly flow overhead would set the stage for a series of disturbances to lift across the broader region. As to be expected, there remain a lot of details to iron out this far out. Nevertheless, this period will be monitored closely for potentially impactful weather systems across the central CONUS. Stay tuned.

Petr

AVIATION /00Z TAFS THROUGH 06Z MONDAY/

Issued at 523 PM CST Sat Nov 22 2025

The only forecast concern this period are the winds. Southwest winds will gust into the 20kt range this evening, mainly for the Chicago area terminals and its possible these gusts end by mid/ late evening as directions turn more west/southwest. A frontal boundary will move across the area tonight, shifting winds to the west/northwest. There may be a brief period along and just behind the front with some gusts in the 15-20kt range, but prevailing speeds should be 10kts or less, which will continue through midday Sunday. Winds will slowly turn more westerly with speeds under 10kts Sunday afternoon and then become light southwest or light southerly early Sunday evening. cms

LOT WATCHES/WARNINGS/ADVISORIES

IL...None. IN...None. LM...Small Craft Advisory from 9 PM this evening to 10 AM CST Sunday for Gary to Burns Harbor IN-Burns Harbor to Michigan City IN.