Edition 2026-09-23 The Ledger Archive API RSS Weather Trader
Milepost
1191

TheForecast Post

A chronicle of American weather and climate  ·  Wednesday, 23 September 2026

Denver, Colorado Revisions MILEPOST 1190

Denver's forecast for Tuesday has moved 11°F colder

77°F in the 20260921T12:00Z run, 66°F in the 20260923T06:00Z — 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 22°F.

Successive cycles do not merely refresh a forecast; they leave a trail. For Tuesday, September 29 at 21Z in Denver, that trail runs from 77.5°F in the 20260921T12:00Z cycle to 66.0°F in the 20260923T06:00Z — a move of -11.4°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)
-11.4 °F normal 0.0 °F · 2 of 8
8 synoptic cycles
10th-to-90th percentile spread at that hour
api.weather.city (nbm-qmd)
22.5 °F normal 11.4 °F
current run
Milepost
1190 · laid 2026-09-23T17:25:13Z
Model
nbm-qmd · cycle 20260923T06:00Z
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
fa0b51a28ad28eb130217612c3fa4e49c911f862ed9ebcd2820a6a270808887d
Machine
JSON