Chicago, Illinois Revisions
MILEPOST 1045
Chicago's forecast for Monday has moved 13°F colder
83°F in the 20260908T18:00Z run, 70°F in the 20260910T12:00Z — 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 Monday, September 14 at 18Z in Chicago, that trail runs from 83.2°F in the 20260908T18:00Z cycle to 69.8°F in the 20260910T12:00Z — a move of -13.4°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 Monday at 18Z api.weather.city /v1/history (nbm-qmd) |
-13.4 °F | normal 0.0 °F · 2 of 9 8 synoptic cycles |
| 10th-to-90th percentile spread at that hour api.weather.city (nbm-qmd) |
19.4 °F | normal 13.4 °F current run |
- Milepost
- 1045 · laid 2026-09-10T22:25:17Z
- Model
- nbm-qmd · cycle 20260910T12:00Z
- 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
- 4783d4ce80df202b2bdd2b1c85986c8de66ff3301f5a324a5496f4a4cb330ea4
- Machine
- JSON