Chicago, Illinois Revisions
MILEPOST 1083
Chicago's forecast for Saturday has moved 13°F warmer
70°F in the 20260912T06:00Z run, 83°F in the 20260914T06:00Z — 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 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 69.6°F in the 20260912T06:00Z cycle to 82.9°F in the 20260914T06:00Z — a move of +13.3°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) |
13.3 °F | normal 0.0 °F · 2 of 9 8 synoptic cycles |
| 10th-to-90th percentile spread at that hour api.weather.city (nbm-qmd) |
20.2 °F | normal 13.3 °F current run |
- Milepost
- 1083 · laid 2026-09-14T16:25:18Z
- Model
- nbm-qmd · cycle 20260914T06:00Z
- 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
- 277ba896a8adc1858d173ddfb627ec1b7ca8968ca468b1a40b948e8bc60f8074
- Machine
- JSON