Edition 2026-09-19 The Ledger Archive API RSS Weather Trader
Milepost
1141

TheForecast Post

A chronicle of American weather and climate  ·  Saturday, 19 September 2026

Atlanta, Georgia Revisions MILEPOST 1138

Atlanta's forecast for Monday has moved 9°F colder

72°F in the 20260917T00:00Z run, 63°F in the 20260918T18:00Z — the 2nd-largest revision of the 6 cities on the roster that moved at all. The current run's 10th-to-90th percentile spread at that hour is 14°F.

Successive cycles do not merely refresh a forecast; they leave a trail. For Monday, September 28 at 06Z in Atlanta, that trail runs from 72.0°F in the 20260917T00:00Z cycle to 63.4°F in the 20260918T18:00Z — a move of -8.6°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 Monday at 06Z
api.weather.city /v1/history (nbm-qmd)
-8.6 °F normal 0.0 °F · 2 of 6
8 synoptic cycles
10th-to-90th percentile spread at that hour
api.weather.city (nbm-qmd)
14.2 °F normal 8.6 °F
current run
Milepost
1138 · laid 2026-09-19T10:25:16Z
Model
nbm-qmd · cycle 20260918T18:00Z
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
448dcc7937822ddafe90dc9c90164e66ea821374e5525de9891bbe01f26810a5
Machine
JSON