Edition 2026-09-29 The Ledger Archive API RSS Weather Trader
Milepost
1240

TheForecast Post

A chronicle of American weather and climate  ·  Tuesday, 29 September 2026

Denver, Colorado Revisions MILEPOST 1239

Denver's forecast for Thursday has moved 13°F colder

71°F in the 20260927T00:00Z run, 58°F in the 20260928T18:00Z — the largest revision of any city on the roster. 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 Thursday, October 1 at 00Z in Denver, that trail runs from 71.0°F in the 20260927T00:00Z cycle to 57.9°F in the 20260928T18:00Z — a move of -13.1°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 Thursday at 00Z
api.weather.city /v1/history (nbm-qmd)
-13.1 °F normal 0.0 °F · 1 of 8
8 synoptic cycles
10th-to-90th percentile spread at that hour
api.weather.city (nbm-qmd)
11.8 °F normal 13.1 °F
current run
Milepost
1239 · laid 2026-09-29T04:25:14Z
Model
nbm-qmd · cycle 20260928T18:00Z
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
769867bd9074c8bb7cd6b1da6e8ada7ba632c6592ca0da7fac44dea613bf0282
Machine
JSON