textproduct: Chicago
This forecast discussion was created in the public domain by the National Weather Service. It can be found in its original form here.
KEY MESSAGES
- The dry and unseasonably mild weather will continue through the upcoming weekend.
DISCUSSION
Issued at 136 PM CDT Wed Oct 21 2026
An anomalously strong mid-level ridge over the central CONUS will anchor omega blocking across much of North America over the next several days. Meanwhile, an elongated surface ridge extending from the Lower Mississippi River Valley to the Canadian Maritimes is in the processes of congealing with another expansive high pressure shifting toward the Upper Great Lakes. As a result, quiet weather with unseasonably warm conditions will continue through the upcoming weekend. As was observed the past few mornings, generally clear skies and light/calm winds should promote shallow fog across primarily interior northern Illinois late tonight through sunrise Thursday.
The blocking pattern will slowly break down early next week as the ridge flattens and a southwestern upper-level low begins to meander toward the central CONUS. A series of smaller troughs on the periphery of a developing longwave trough across the north Pacific and western Canada will eventually pick up the southwestern low. Consensus guidance suggests that the influence of the low on our area could occur as early as Monday night, but more likely Tuesday and Wednesday. Cooler and more seasonable conditions would accompany this system.
Kluber
AVIATION /18Z TAFS THROUGH 00Z FRIDAY/
Issued at 1217 PM CDT Wed Oct 21 2026
Expect generally VFR conditions with a few mid-level clouds through the period as high pressure drifts over the area. However, as has been observed during the past few mornings, MIFG/BCFG is likely at RFD/DPA and VFR BR is possible at ORD late tonight through sunrise Thursday.
Light SW winds are expected this afternoon, though a weak lake breeze may wash out and turn winds SE 5 knots or less over ORD and especially MDW toward sunset. Winds will become calm or light and VRB tonight into Thursday morning, with a lake- enhanced NE wind shift likely by Thursday afternoon.
Kluber
LOT WATCHES/WARNINGS/ADVISORIES
IL...None. IN...None. LM...None.
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