Chicago, Illinois Revisions
MILEPOST 1490
Chicago's forecast for Friday has moved 13°F warmer
58°F in the 20261022T12:00Z run, 71°F in the 20261024T06:00Z — the 2nd-largest revision of the 5 cities on the roster that moved at all. The current run's 10th-to-90th percentile spread at that hour is 13°F.
Successive cycles do not merely refresh a forecast; they leave a trail. For Friday, October 30 at 21Z in Chicago, that trail runs from 58.3°F in the 20261022T12:00Z cycle to 70.9°F in the 20261024T06:00Z — a move of +12.6°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 Friday at 21Z api.weather.city /v1/history (nbm-qmd) |
12.6 °F | normal 0.0 °F · 2 of 5 8 synoptic cycles |
| 10th-to-90th percentile spread at that hour api.weather.city (nbm-qmd) |
12.9 °F | normal 12.6 °F current run |
- Milepost
- 1490 · laid 2026-10-24T16:25:23Z
- Model
- nbm-qmd · cycle 20261024T06:00Z
- 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
- 0fe83b96838a7fd6232e38c31867b8fad0076cd51a2b25285eb0e7d4663f5e60
- Machine
- JSON