Chicago, Illinois Revisions
MILEPOST 1056
Chicago's forecast for Monday has moved 16°F colder
85°F in the 20260909T18:00Z run, 69°F in the 20260911T12:00Z — the 2nd-largest revision of the 8 cities on the roster that moved at all. The current run's 10th-to-90th percentile spread at that hour is 7°F.
Successive cycles do not merely refresh a forecast; they leave a trail. For Monday, September 14 at 21Z in Chicago, that trail runs from 85.3°F in the 20260909T18:00Z cycle to 69.0°F in the 20260911T12:00Z — a move of -16.4°F across 8 runs.
The change is larger than the run's own 10th-to-90th percentile spread — the guidance did not merely narrow, it moved off its previous position.
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 21Z api.weather.city /v1/history (nbm-qmd) |
-16.4 °F | normal 0.0 °F · 2 of 8 8 synoptic cycles |
| 10th-to-90th percentile spread at that hour api.weather.city (nbm-qmd) |
7.2 °F | normal 16.4 °F current run |
- Milepost
- 1056 · laid 2026-09-11T22:25:11Z
- Model
- nbm-qmd · cycle 20260911T12:00Z
- 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
- 95537feb2e0f250a868223a5a41fa0af45f46e50b472d71f5161c6b7805057c4
- Machine
- JSON