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Milepost
1531

TheForecast Post

A chronicle of American weather and climate  ·  Friday, 30 October 2026

Boston, Massachusetts Revisions MILEPOST 1529

Boston's forecast for Wednesday has moved 8°F warmer

57°F in the 20261027T18:00Z run, 64°F in the 20261029T12:00Z — the 2nd-largest revision of the 5 cities on the roster that moved at all. The current run's 10th-to-90th percentile spread at that hour is 16°F.

Successive cycles do not merely refresh a forecast; they leave a trail. For Wednesday, November 4 at 18Z in Boston, that trail runs from 56.9°F in the 20261027T18:00Z cycle to 64.5°F in the 20261029T12:00Z — a move of +7.6°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 Wednesday at 18Z
api.weather.city /v1/history (nbm-qmd)
7.6 °F normal 0.0 °F · 2 of 5
8 synoptic cycles
10th-to-90th percentile spread at that hour
api.weather.city (nbm-qmd)
16 °F normal 7.6 °F
current run
Milepost
1529 · laid 2026-10-29T22:25:23Z
Model
nbm-qmd · cycle 20261029T12:00Z
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
9917be6391633f7d7305caa9d65a23d12c97e3413b040ea6f9fadb51173c72bf
Machine
JSON