Chicago, Illinois Revisions
MILEPOST 1261
Chicago's forecast for Sunday has moved 8°F warmer
56°F in the 20260929T12:00Z run, 65°F in the 20261001T06:00Z — the 2nd-largest revision of the 7 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 Sunday, October 11 at 00Z in Chicago, that trail runs from 56.4°F in the 20260929T12:00Z cycle to 64.5°F in the 20261001T06:00Z — a move of +8.1°F across 8 runs.
The change sits well inside the run's own spread, which is the guidance converging rather than reversing.
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 Sunday at 00Z api.weather.city /v1/history (nbm-qmd) |
8.1 °F | normal 0.0 °F · 2 of 7 8 synoptic cycles |
| 10th-to-90th percentile spread at that hour api.weather.city (nbm-qmd) |
18.4 °F | normal 8.1 °F current run |
- Milepost
- 1261 · laid 2026-10-01T16:25:12Z
- Model
- nbm-qmd · cycle 20261001T06:00Z
- 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
- ae719b5c55159e676897b1dbd2eb1b37211d56087e40b33b320807c153d5276e
- Machine
- JSON