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Milepost
1143

TheForecast Post

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

New York, New York Revisions MILEPOST 1143

New York's forecast for Friday has moved 6°F colder

69°F in the 20260917T12:00Z run, 63°F in the 20260919T06:00Z — 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 19°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 69.0°F in the 20260917T12:00Z cycle to 62.6°F in the 20260919T06:00Z — 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 Friday 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)
19.1 °F normal 6.3 °F
current run
Milepost
1143 · laid 2026-09-19T16:25:23Z
Model
nbm-qmd · cycle 20260919T06:00Z
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
061294aed87dd9a2d3417162589a9eff1f94f4bf1b248cecd6a1851fc56e004a
Machine
JSON