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Milepost
1195

TheForecast Post

A chronicle of American weather and climate  ·  Thursday, 24 September 2026

Denver, Colorado Revisions MILEPOST 1193

Denver's forecast for Tuesday has moved 16°F colder

77°F in the 20260921T18:00Z run, 61°F in the 20260923T18:00Z — the largest revision of any city on the roster. 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 77.0°F in the 20260921T18:00Z cycle to 61.4°F in the 20260923T18:00Z — a move of -15.6°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 Tuesday at 21Z
api.weather.city /v1/history (nbm-qmd)
-15.6 °F normal 0.0 °F · 1 of 8
8 synoptic cycles
10th-to-90th percentile spread at that hour
api.weather.city (nbm-qmd)
21.9 °F normal 15.6 °F
current run
Milepost
1193 · laid 2026-09-24T04:25:17Z
Model
nbm-qmd · cycle 20260923T18:00Z
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
bbe1ebe4df1f04f14eed26d66b5a25d0316267cf392fb392d2b2bf63353d543a
Machine
JSON