Chicago, Illinois Revisions
MILEPOST 1086
Chicago's forecast for Saturday has moved 12°F warmer
70°F in the 20260912T12:00Z run, 82°F in the 20260914T12:00Z — the 2nd-largest revision of the 9 cities on the roster that moved at all. The current run's 10th-to-90th percentile spread at that hour is 19°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 70.0°F in the 20260912T12:00Z cycle to 82.0°F in the 20260914T12:00Z — a move of +12.0°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 Saturday at 21Z api.weather.city /v1/history (nbm-qmd) |
12 °F | normal 0.0 °F · 2 of 9 8 synoptic cycles |
| 10th-to-90th percentile spread at that hour api.weather.city (nbm-qmd) |
18.7 °F | normal 12.0 °F current run |
- Milepost
- 1086 · laid 2026-09-14T22:25:12Z
- Model
- nbm-qmd · cycle 20260914T12:00Z
- 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
- a35d9f97ca520088ddcee40b2ada80b883236d991c79d9dc2df9ad066c3883ee
- Machine
- JSON