Edition 2026-09-21 The Ledger Archive API RSS Weather Trader
Milepost
1166

TheForecast Post

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

Atlanta, Georgia Revisions MILEPOST 1166

Atlanta's forecast for Wednesday has moved 6°F warmer

63°F in the 20260919T06:00Z run, 69°F in the 20260921T00:00Z — the 2nd-largest revision of the 2 cities on the roster that moved at all. The current run's 10th-to-90th percentile spread at that hour is 11°F.

Successive cycles do not merely refresh a forecast; they leave a trail. For Wednesday, September 30 at 12Z in Atlanta, that trail runs from 62.9°F in the 20260919T06:00Z cycle to 69.0°F in the 20260921T00:00Z — a move of +6.1°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 Wednesday at 12Z
api.weather.city /v1/history (nbm-qmd)
6.1 °F normal 0.0 °F · 2 of 2
8 synoptic cycles
10th-to-90th percentile spread at that hour
api.weather.city (nbm-qmd)
10.8 °F normal 6.1 °F
current run
Milepost
1166 · laid 2026-09-21T10:25:18Z
Model
nbm-qmd · cycle 20260921T00:00Z
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
4d50010fd7d1a00078b0bb755fe15bf1972066fd62a1cfff1065b72f19e4bf0d
Machine
JSON