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Milepost
1119

TheForecast Post

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

New York, New York Revisions MILEPOST 1117

New York's forecast for Tuesday has moved 10°F colder

72°F in the 20260915T06:00Z run, 62°F in the 20260917T00:00Z — the largest revision of any city on the roster. The current run's 10th-to-90th percentile spread at that hour is 11°F.

Successive cycles do not merely refresh a forecast; they leave a trail. For Tuesday, September 22 at 18Z in New York, that trail runs from 71.9°F in the 20260915T06:00Z cycle to 61.8°F in the 20260917T00:00Z — a move of -10.1°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 Tuesday at 18Z
api.weather.city /v1/history (nbm-qmd)
-10.1 °F normal 0.0 °F · 1 of 3
8 synoptic cycles
10th-to-90th percentile spread at that hour
api.weather.city (nbm-qmd)
11.1 °F normal 10.1 °F
current run
Milepost
1117 · laid 2026-09-17T11:25:16Z
Model
nbm-qmd · cycle 20260917T00:00Z
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
c7c4b4f28e5bf0137299c55a8a438b5c22c941748740d4cef13600da11b31573
Machine
JSON