Edition 2026-09-21 The Ledger Archive API RSS Weather Trader
Milepost
1169

TheForecast Post

A chronicle of American weather and climate  ·  Monday, 21 September 2026

Denver, Colorado Revisions MILEPOST 1168

Denver's forecast for Friday has moved 8°F colder

79°F in the 20260919T12:00Z run, 70°F in the 20260921T06:00Z — 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 15°F.

Successive cycles do not merely refresh a forecast; they leave a trail. For Friday, September 25 at 00Z in Denver, that trail runs from 78.6°F in the 20260919T12:00Z cycle to 70.4°F in the 20260921T06:00Z — a move of -8.2°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 00Z
api.weather.city /v1/history (nbm-qmd)
-8.2 °F normal 0.0 °F · 2 of 5
8 synoptic cycles
10th-to-90th percentile spread at that hour
api.weather.city (nbm-qmd)
15.3 °F normal 8.2 °F
current run
Milepost
1168 · laid 2026-09-21T16:25:13Z
Model
nbm-qmd · cycle 20260921T06:00Z
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
908243ed785eb6a67abc52dc8ab226ca9eb17c67b71dda75054a6d628527f67e
Machine
JSON