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Milepost
1157

TheForecast Post

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

Dallas, Texas Revisions MILEPOST 1154

Dallas's forecast for Wednesday has moved 10°F colder

92°F in the 20260919T06:00Z run, 82°F in the 20260920T06:00Z — the largest revision of any city on the roster. The current run's 10th-to-90th percentile spread at that hour is 23°F.

Successive cycles do not merely refresh a forecast; they leave a trail. For Wednesday, September 30 at 18Z in Dallas, that trail runs from 92.4°F in the 20260919T06:00Z cycle to 81.9°F in the 20260920T06:00Z — a move of -10.5°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 Wednesday at 18Z
api.weather.city /v1/history (nbm-qmd)
-10.5 °F normal 0.0 °F · 1 of 3
8 synoptic cycles
10th-to-90th percentile spread at that hour
api.weather.city (nbm-qmd)
22.8 °F normal 10.5 °F
current run
Milepost
1154 · laid 2026-09-20T17:25:19Z
Model
nbm-qmd · cycle 20260920T06:00Z
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
6c659402b3649078c031b1b6aa2689ec55e3a820f10ba536f15023beaac80e76
Machine
JSON