Edition 2026-09-17 The Ledger Archive API RSS Weather Trader
Milepost
1119

TheForecast Post

A chronicle of American weather and climate  ·  Thursday, 17 September 2026

Salt Lake City, Utah Revisions MILEPOST 1116

Salt Lake City's forecast for Saturday has moved 9°F colder

77°F in the 20260915T06:00Z run, 69°F in the 20260916T18:00Z — the 3rd-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 4°F.

Successive cycles do not merely refresh a forecast; they leave a trail. For Saturday, September 19 at 21Z in Salt Lake City, that trail runs from 77.2°F in the 20260915T06:00Z cycle to 68.5°F in the 20260916T18:00Z — a move of -8.7°F across 8 runs.

The change is larger than the run's own 10th-to-90th percentile spread — the guidance did not merely narrow, it moved off its previous position.

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 21Z
api.weather.city /v1/history (nbm-qmd)
-8.7 °F normal 0.0 °F · 3 of 4
8 synoptic cycles
10th-to-90th percentile spread at that hour
api.weather.city (nbm-qmd)
4.5 °F normal 8.7 °F
current run
Milepost
1116 · laid 2026-09-17T10:25:25Z
Model
nbm-qmd · cycle 20260916T18:00Z
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
7d696fbe97415b0bf51bb051f649d3535f60b36a72ca46f849ae86d12a011d68
Machine
JSON