textproduct: Chicago

KEY MESSAGES

- Lake effect rain showers may periodically affect portions of Porter County, IN through this evening.

- Below freezing temperatures are expected across a large portion of northern Illinois tonight. Near or below freezing temperatures may then be observed once again Saturday night and Sunday night in some locations.

- Dry conditions and a warming trend are expected this weekend into early next week.

DISCUSSION

Issued at 1252 PM CST Fri Nov 6 2026

The coldest airmass so far this season over the area has led to temps struggling to rise out of the mid 40s early this afternoon, with 50 degrees looking to be out of reach for a vast majority of the area. With a surface ridge drifting toward the area from the west, limited non-diurnal cloud cover upstream, and cool daytime temps, we are well on our way to the coldest night and first hard freeze for many this fall. Do have some concern that shallow stratus attempts to expand inland off Lake Michigan this evening, but lowering inversion heights through the night should erode any potential lingering stratus overnight. Overall, temps tonight are expected to fall into the mid to upper 20s away from the core of the Chicago metro and northwest Indiana downwind of Lake Michigan. In colder areas tonight, shallow fog may develop in lieu of heavy frost. Otherwise, isolated lake effect rain showers will persist into mainly northern Porter County through early evening before exiting to the east.

A series of weak mid-level troughs and ridges within broader WNW flow aloft will cross the northern Great Lakes through early next week, leading to precip-free conditions and daytime highs gradually moderating back to the low to mid 60s Monday and Tuesday.

Consensus ensemble guidance suggests that an increasingly amplified mid-level pattern with hints at a developing omega block will develop across much of North America late next week/weekend. The eastern trough of this pattern does show signs of settling over the Great Lakes region during this period. With the main ridge situated in a SSW to NNE orientation into Hudson Bay, seasonably cool temps and north to northeast low- level flow will support periods of lake effect rain showers aimed into both northwest Indiana and northeast Illinois. Cannot fully rule out our first snow flakes of the season given some ensemble members supporting a more westward presentation of the trough and corresponding colder airmass. Will need to keep a close eye on any trends toward colder solutions as early as Thursday morning but especially into Friday.

Kluber

AVIATION /00Z TAFS THROUGH 06Z SUNDAY/

Issued at 543 PM CST Fri Nov 6 2026

Forecast concerns include...

Wind directions this evening. Mvfr cigs across northwest IN tonight.

A lake breeze moved inland and reached ORD/MDW this afternoon, shifting winds to the northeast. This boundary is now dissipating and light north/northeast winds at ORD/MDW will become light north/northwest over the next 1-2 hours and then turn more northwesterly tonight and westerly Saturday. Speeds may increase back near 10kts on Saturday.

Mvfr cigs can be expected across northwest IN this evening and possibly persisting into the overnight hours. Low vfr cigs remain across the Chicago terminals and these are expected to scatter out later this evening though only medium confidence for timing. The longer these low vfr cigs persist, the better the chance they may lower to high mvfr and will need to monitor trends until they finally scatter out.

There is the potential for some patchy/shallow fog toward daybreak Saturday morning. Low level winds appear to remain strong enough to keep the low levels mixed, that the fog potential appears low and no mention at any of the terminals for now. cms

LOT WATCHES/WARNINGS/ADVISORIES

IL...None. IN...None. LM...Small Craft Advisory until 3 AM CST Saturday for the IL nearshore waters.

Small Craft Advisory until 9 AM CST Saturday for Calumet Harbor IL to Burns Harbor IN.

Small Craft Advisory until 3 PM CST Saturday for Burns Harbor to Michigan City IN.