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Milepost
1150

TheForecast Post

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

Atlanta, Georgia Revisions MILEPOST 1150

Atlanta's forecast for Thursday has moved 6°F colder

81°F in the 20260918T00:00Z run, 75°F in the 20260919T18:00Z — the 3rd-largest revision of the 3 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 Thursday, September 24 at 18Z in Atlanta, that trail runs from 81.2°F in the 20260918T00:00Z cycle to 74.9°F in the 20260919T18:00Z — a move of -6.3°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 Thursday at 18Z
api.weather.city /v1/history (nbm-qmd)
-6.3 °F normal 0.0 °F · 3 of 3
8 synoptic cycles
10th-to-90th percentile spread at that hour
api.weather.city (nbm-qmd)
14.2 °F normal 6.3 °F
current run
Milepost
1150 · laid 2026-09-20T06:26:38Z
Model
nbm-qmd · cycle 20260919T18:00Z
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
3a940fb57e1e8bcc0ddd70d6d7bea331aaff27cbd0a544974f69cea402e77d50
Machine
JSON