Edition 2026-09-20 The Ledger Archive API RSS Weather Trader
Milepost
1153

TheForecast Post

A chronicle of American weather and climate  ·  Sunday, 20 September 2026

Nashville, Tennessee Revisions MILEPOST 1152

Nashville's forecast for Saturday has moved 6°F colder

84°F in the 20260918T06:00Z run, 78°F in the 20260920T00:00Z — the 2nd-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 12°F.

Successive cycles do not merely refresh a forecast; they leave a trail. For Saturday, September 26 at 18Z in Nashville, that trail runs from 84.2°F in the 20260918T06:00Z cycle to 77.8°F in the 20260920T00:00Z — a move of -6.5°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 Saturday at 18Z
api.weather.city /v1/history (nbm-qmd)
-6.5 °F normal 0.0 °F · 2 of 4
8 synoptic cycles
10th-to-90th percentile spread at that hour
api.weather.city (nbm-qmd)
11.7 °F normal 6.5 °F
current run
Milepost
1152 · laid 2026-09-20T10:25:16Z
Model
nbm-qmd · cycle 20260920T00:00Z
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
23f675413a3dda2240c357128aaf193bfacb5678ef14bb17a87337da0f2a8320
Machine
JSON