Chicago, Illinois Revisions
MILEPOST 1092
Chicago's forecast for Saturday has moved 8°F warmer
71°F in the 20260913T06:00Z run, 79°F in the 20260915T00:00Z — the 3rd-largest revision of the 4 cities on the roster that moved at all. The current run's 10th-to-90th percentile spread at that hour is 16°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 71.2°F in the 20260913T06:00Z cycle to 79.4°F in the 20260915T00:00Z — a move of +8.2°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) |
8.2 °F | normal 0.0 °F · 3 of 4 8 synoptic cycles |
| 10th-to-90th percentile spread at that hour api.weather.city (nbm-qmd) |
15.7 °F | normal 8.2 °F current run |
- Milepost
- 1092 · laid 2026-09-15T10:25:13Z
- Model
- nbm-qmd · cycle 20260915T00:00Z
- 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
- 7e26b29c6dbb82faca030229ed8162a5bee51393907bdfe67c54bbded7f7d769
- Machine
- JSON