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Milepost
1173

TheForecast Post

A chronicle of American weather and climate  ·  Tuesday, 22 September 2026

Minneapolis, Minnesota Revisions MILEPOST 1170

Minneapolis's forecast for Saturday has moved 9°F colder

72°F in the 20260919T18:00Z run, 63°F in the 20260921T12:00Z — the largest revision of any city on the roster. The current run's 10th-to-90th percentile spread at that hour is 10°F.

Successive cycles do not merely refresh a forecast; they leave a trail. For Saturday, September 26 at 21Z in Minneapolis, that trail runs from 72.1°F in the 20260919T18:00Z cycle to 63.3°F in the 20260921T12:00Z — a move of -8.8°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 Saturday at 21Z
api.weather.city /v1/history (nbm-qmd)
-8.8 °F normal 0.0 °F · 1 of 5
8 synoptic cycles
10th-to-90th percentile spread at that hour
api.weather.city (nbm-qmd)
10 °F normal 8.8 °F
current run
Milepost
1170 · laid 2026-09-21T22:25:13Z
Model
nbm-qmd · cycle 20260921T12:00Z
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
2d16ec3d68a0fa83778ce967b3ee4273167056c179fa1f66930eace53907773a
Machine
JSON