python-metar (personal fork)

Personal fork of python-metar/python-metar with pilot-friendly extensions and Slack-bot scaffolding.

The upstream parser is unchanged in spirit — it still decodes METAR/SPECI weather reports. This fork adds:

• Flight category classifier — VFR / MVFR / IFR / LIFR per FAA thresholds
• Plain-English output layer — human-readable summary for non-pilots
• Crosswind / headwind helper — pure math for runway planning
• Expanded remarks coverage — TSNO, PWINO, FZRANO, RVRNO, $, VIRGA, FROPA, PRESRR, PRESFR, variable ceiling, variable visibility, surface and tower visibility
• Slack-bot scaffolding — fetch / airports / Block Kit formatter / AWS Lambda handler

Module layout

Module	Purpose
metar.parser	The METAR / SPECI parser. Defines the Metar class.
metar.datatypes	Unit-aware value types: temperature, pressure, speed, distance, direction, precipitation.
metar.station	ICAO -> station-metadata lookup using the bundled NSD data. Sparse for US stations.
metar.analysis	Free functions over a parsed Metar: ceiling, flight_category, relative_humidity, wind_components.
metar.format	Plain-English / sentence formatters. Used by to_plain_english.
metar.fetch	Stdlib HTTP client for the aviationweather.gov API.
metar.airports	Small curated ICAO -> airport-name / runways table.
metar.slack	Slack Block Kit formatter.
lambda_handler.py	AWS Lambda entry point for the /metar slash command.

The historical from metar import Metar and from metar import Station imports still work via aliases in metar/__init__.py.

Quick start

from metar.parser import Metar
from metar.airports import lookup
from metar.format import to_plain_english

m = Metar("METAR KOAK 050153Z 26008KT 10SM CLR 17/11 A2989 RMK AO2 SLP121")
print(m.flight_category())            # VFR
print(m.ceiling())                    # None  (CLR = no ceiling)
print(to_plain_english(m, station_name=lookup("KOAK").name))

🟢 VFR | KOAK — Oakland Int'l | observed 01:53Z

Winds west at 8 knots. Visibility 10 miles. Clear skies, no ceiling.
Temperature 63°F (17°C), dewpoint 51°F (11°C), humidity 65%.
Altimeter 29.89 inHg. Sea level pressure 1012.1 hPa.
Station is automated (AO2).

Slack bot

End goal is a Lambda-backed /metar KOAK slash command. The pieces:

from metar.fetch import fetch_metar
from metar.slack import to_slack_blocks
from metar.airports import lookup

m = fetch_metar("KOAK")
payload = to_slack_blocks(m, station_name=lookup("KOAK").name)
# payload is now a dict; json.dumps() it into a Slack response body.

lambda_handler.py ties this to API Gateway + Slack signature verification. Set SLACK_SIGNING_SECRET in the Lambda environment before deploying.

Tests

python3 -m venv .venv
.venv/bin/pip install -e .[tests]
.venv/bin/python -m pytest -q

Currently 147 tests, all passing.

License

BSD 2-Clause, inherited from upstream. See LICENSE.