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Milepost
1165

TheForecast Post

A chronicle of American weather and climate  ·  Monday, 21 September 2026

New York, New York Revisions MILEPOST 1164

New York's forecast for Saturday has moved 7°F colder

70°F in the 20260919T00:00Z run, 63°F in the 20260920T18:00Z — the 2nd-largest revision of the 2 cities on the roster that moved at all. The current run's 10th-to-90th percentile spread at that hour is 17°F.

Successive cycles do not merely refresh a forecast; they leave a trail. For Saturday, September 26 at 18Z in New York, that trail runs from 69.7°F in the 20260919T00:00Z cycle to 62.8°F in the 20260920T18:00Z — a move of -6.9°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 Saturday at 18Z
api.weather.city /v1/history (nbm-qmd)
-6.9 °F normal 0.0 °F · 2 of 2
8 synoptic cycles
10th-to-90th percentile spread at that hour
api.weather.city (nbm-qmd)
16.9 °F normal 6.9 °F
current run
Milepost
1164 · laid 2026-09-21T05:26:31Z
Model
nbm-qmd · cycle 20260920T18:00Z
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
d9a1a6ef0290937e5e70cc8246444479d8e545b10b3cd7aa29b072f4f5421f8a
Machine
JSON