Edition 2026-09-18 The Ledger Archive API RSS Weather Trader
Milepost
1134

TheForecast Post

A chronicle of American weather and climate  ·  Friday, 18 September 2026

Nashville, Tennessee Revisions MILEPOST 1132

Nashville's forecast for Sunday has moved 10°F colder

69°F in the 20260916T18:00Z run, 59°F in the 20260918T12:00Z — the largest revision of any city on the roster. The current run's 10th-to-90th percentile spread at that hour is 16°F.

Successive cycles do not merely refresh a forecast; they leave a trail. For Sunday, September 27 at 12Z in Nashville, that trail runs from 68.9°F in the 20260916T18:00Z cycle to 59.3°F in the 20260918T12:00Z — a move of -9.6°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 Sunday at 12Z
api.weather.city /v1/history (nbm-qmd)
-9.6 °F normal 0.0 °F · 1 of 6
8 synoptic cycles
10th-to-90th percentile spread at that hour
api.weather.city (nbm-qmd)
15.8 °F normal 9.6 °F
current run
Milepost
1132 · laid 2026-09-18T22:25:15Z
Model
nbm-qmd · cycle 20260918T12:00Z
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
f043e16db051f8f98e46b8f435ae77b96efea55ce0da5b4f536a977572c3c156
Machine
JSON