Edition 2026-09-21 The Ledger Archive API RSS Weather Trader
Milepost
1165

TheForecast Post

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

Nashville, Tennessee Revisions MILEPOST 1165

Nashville's forecast for Monday has moved 7°F colder

66°F in the 20260919T00:00Z run, 59°F in the 20260920T18:00Z — the 3rd-largest revision of the 4 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 Monday, September 28 at 12Z in Nashville, that trail runs from 66.3°F in the 20260919T00:00Z cycle to 59.1°F in the 20260920T18:00Z — a move of -7.2°F across 8 runs.

The change sits well inside the run's own spread, which is the guidance converging rather than reversing.

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 Monday at 12Z
api.weather.city /v1/history (nbm-qmd)
-7.2 °F normal 0.0 °F · 3 of 4
8 synoptic cycles
10th-to-90th percentile spread at that hour
api.weather.city (nbm-qmd)
14.8 °F normal 7.2 °F
current run
Milepost
1165 · laid 2026-09-21T06:28:50Z
Model
nbm-qmd · cycle 20260920T18:00Z
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
3066361ecbe98c7a0a94ccc58d9bcd0be78789361f733b7be06fe937614e31fc
Machine
JSON