Chicago, Illinois Revisions
MILEPOST 1446
Chicago's forecast for Wednesday has moved 12°F colder
61°F in the 20261018T12:00Z run, 49°F in the 20261020T06:00Z — the 2nd-largest revision of the 10 cities on the roster that moved at all. The current run's 10th-to-90th percentile spread at that hour is 18°F.
Successive cycles do not merely refresh a forecast; they leave a trail. For Wednesday, October 28 at 00Z in Chicago, that trail runs from 61.1°F in the 20261018T12:00Z cycle to 49.4°F in the 20261020T06:00Z — a move of -11.7°F across 8 runs.
The change is about half the run's 10th-to-90th percentile spread, so the earlier forecast is still inside the current range of outcomes.
Model NBM-QMD, via api.weather.city /v1/history. Percentiles are the same run's own.
The numbers in this piece, with what they are measured against
| forecast revision for Wednesday at 00Z api.weather.city /v1/history (nbm-qmd) |
-11.7 °F | normal 0.0 °F · 2 of 10 8 synoptic cycles |
| 10th-to-90th percentile spread at that hour api.weather.city (nbm-qmd) |
17.6 °F | normal 11.7 °F current run |
- Milepost
- 1446 · laid 2026-10-20T16:25:19Z
- Model
- nbm-qmd · cycle 20261020T06:00Z
- Desk
- revision v1
- Method
- the same valid time read from successive synoptic cycles; the move is last run minus first run
- Source
- https://api.weather.city/v1/history
- Digest
- 10c4b8604f6ac9bb54e415e88466194f042705e5e82ccb6c040f2e9cefcde935
- Machine
- JSON