Chicago, Illinois Revisions
MILEPOST 1066
Chicago's forecast for Tuesday has moved 10°F warmer
74°F in the 20260910T18:00Z run, 84°F in the 20260912T12:00Z — the 2nd-largest revision of the 7 cities on the roster that moved at all. The current run's 10th-to-90th percentile spread at that hour is 12°F.
Successive cycles do not merely refresh a forecast; they leave a trail. For Tuesday, September 15 at 21Z in Chicago, that trail runs from 74.2°F in the 20260910T18:00Z cycle to 84.5°F in the 20260912T12:00Z — a move of +10.3°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 Tuesday at 21Z api.weather.city /v1/history (nbm-qmd) |
10.3 °F | normal 0.0 °F · 2 of 7 8 synoptic cycles |
| 10th-to-90th percentile spread at that hour api.weather.city (nbm-qmd) |
12.2 °F | normal 10.3 °F current run |
- Milepost
- 1066 · laid 2026-09-12T22:25:12Z
- Model
- nbm-qmd · cycle 20260912T12:00Z
- 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
- f15bbcacfb0c7241c0f5a8844fe847aa0aaeed2d60ba6ef6ef7cd7d31e2a9914
- Machine
- JSON