Chicago, Illinois Revisions
MILEPOST 1096
Chicago's forecast for Saturday has moved 7°F warmer
71°F in the 20260913T12:00Z run, 78°F in the 20260915T06:00Z — the 3rd-largest revision of the 5 cities on the roster that moved at all. The current run's 10th-to-90th percentile spread at that hour is 20°F.
Successive cycles do not merely refresh a forecast; they leave a trail. For Saturday, September 19 at 21Z in Chicago, that trail runs from 70.7°F in the 20260913T12:00Z cycle to 77.9°F in the 20260915T06:00Z — a move of +7.3°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 Saturday at 21Z api.weather.city /v1/history (nbm-qmd) |
7.3 °F | normal 0.0 °F · 3 of 5 8 synoptic cycles |
| 10th-to-90th percentile spread at that hour api.weather.city (nbm-qmd) |
19.6 °F | normal 7.3 °F current run |
- Milepost
- 1096 · laid 2026-09-15T17:25:47Z
- Model
- nbm-qmd · cycle 20260915T06:00Z
- 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
- cfcbddc7be6c36ecaee362563e323a419b68e6d39d0deb9c025ebe7303bb68db
- Machine
- JSON