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Milepost
1137

TheForecast Post

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

New York, New York Revisions MILEPOST 1136

New York's forecast for Friday has moved 9°F colder

72°F in the 20260917T00:00Z run, 63°F in the 20260918T18:00Z — the largest revision of any city on the roster. The current run's 10th-to-90th percentile spread at that hour is 18°F.

Successive cycles do not merely refresh a forecast; they leave a trail. For Friday, September 25 at 18Z in New York, that trail runs from 72.3°F in the 20260917T00:00Z cycle to 62.9°F in the 20260918T18:00Z — a move of -9.5°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 Friday at 18Z
api.weather.city /v1/history (nbm-qmd)
-9.5 °F normal 0.0 °F · 1 of 8
8 synoptic cycles
10th-to-90th percentile spread at that hour
api.weather.city (nbm-qmd)
18 °F normal 9.5 °F
current run
Milepost
1136 · laid 2026-09-19T04:25:25Z
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
af8755367919512bded9e5c841d1f4689b34e8e500e0c9157844fac9ccc0faac
Machine
JSON