@cyanheads/aviation-weather-mcp-server
Fetch METARs, TAFs, PIREPs, domestic/international SIGMETs and CWAs from NWS AWC via MCP. AIRMETs not served. STDIO or Streamable HTTP.
5 Tools • 1 Resource • 1 Prompt
[](./CHANGELOG.md) [](./LICENSE) [](https://github.com/users/cyanheads/packages/container/package/aviation-weather-mcp-server) [](https://modelcontextprotocol.io/) [](https://www.npmjs.com/package/@cyanheads/aviation-weather-mcp-server) [](https://www.typescriptlang.org/) [](https://bun.sh/)
[](https://github.com/cyanheads/aviation-weather-mcp-server/releases/latest/download/aviation-weather-mcp-server.mcpb) [](https://cursor.com/en/install-mcp?name=aviation-weather-mcp-server&config=eyJjb21tYW5kIjoibnB4IiwiYXJncyI6WyIteSIsIkBjeWFuaGVhZHMvYXZpYXRpb24td2VhdGhlci1tY3Atc2VydmVyIl19) [](https://vscode.dev/redirect?url=vscode:mcp/install?%7B%22name%22%3A%22aviation-weather-mcp-server%22%2C%22command%22%3A%22npx%22%2C%22args%22%3A%5B%22-y%22%2C%22%40cyanheads%2Faviation-weather-mcp-server%22%5D%7D)
[](https://www.npmjs.com/package/@cyanheads/mcp-ts-core)
**Public Hosted Server:** [https://aviation-weather.caseyjhand.com/mcp](https://aviation-weather.caseyjhand.com/mcp)
---
## Overview
Aviation weather from the NWS Aviation Weather Center — METARs, TAFs, PIREPs, domestic/international SIGMETs, and Center Weather Advisories. Look up stations, fetch current and forecast conditions, and pull pilot reports and hazard advisories. AIRMETs are not served.
### Tools
| Tool | Description |
|:-----|:------------|
| `aviation_find_stations` | Resolve airports and weather stations by identifier, bounding box, or US state. Returns ICAO/IATA/FAA IDs, coordinates, elevation, and available data types. |
| `aviation_get_metar` | Get current weather observations (METARs) for named airports, or survey every reporting station in a bounding box. Returns decoded wind, visibility, ceiling, present weather, temp/dewpoint, altimeter, cloud layers, flight category (VFR/MVFR/IFR/LIFR), and the raw METAR string. |
| `aviation_get_taf` | Get Terminal Aerodrome Forecasts for one or more airports. Returns each forecast period with valid times, surface wind, low-level wind shear, visibility, decoded weather, cloud layers, and vertical visibility into a forecast obscuration, plus the raw TAF string. |
| `aviation_get_pireps` | Get recent Pilot Reports near an airport or within a bounding box. Returns decoded turbulence, icing, clouds, temperature, wind aloft, flight weather, braking action, altitude, aircraft type, and the raw report. |
| `aviation_get_advisories` | Get domestic/international SIGMETs and Center Weather Advisories. Returns source coverage, hazard, severity, altitude, validity, movement, multipart geometry and original bulletins; omitted facts stay null. |
### Prompts
| Prompt | Description |
|:-----|:------------|
| `aviation_preflight_brief` | Structure a preflight weather briefing for a flight, calling the tools above in sequence and synthesizing a weather-risk summary. |
### Resources
| Resource | Description |
|:---------|:------------|
| `skill://aviation-weather-guide/SKILL.md` | [Aviation weather guide](./skills/aviation-weather-guide/SKILL.md) for regional surveys, airport comparisons, and route assessments, with station identity, forecast timing, and incomplete coverage reconciled before drawing conclusions. |
---
## Capability reference
### `aviation_find_stations` tool
- Look up one or more stations by identifier (up to 20 per call) — a lookup matches the registry's own ID, which for an airport is its 4-character ICAO ID (e.g., `KSEA`, `K0S9`); a 3-letter IATA code never resolves, though each record includes its IATA/FAA aliases when available
- Discover stations within a geographic bounding box, or list stations for one of the 50 US states or DC via two-letter USPS code
- Returns `data_types` (METAR, TAF, etc.) so agents can confirm what's available before querying
- Every result states whether the upstream 400-row cap cut it; complete state snapshots are outside that cap. `limit` (1–400) bounds how many stations a `bbox` or `state` search returns, ordered by ICAO identifier ascending with identifier-less stations last — rejected alongside `station_ids`, since that mode already names the set. An area search returning more than 110 stations with no `limit` says so and names the lever; omitting `limit` still returns every match
- An ID lookup names every identifier that resolved to nothing, separating a 3-letter IATA code (never resolves) from an identifier the registry simply does not list
- Comma-separated entries are split and each token trimmed once; the expanded list must contain 1–20 identifiers, with no empty tokens
- State searches select US registry membership from a complete station snapshot refreshed on demand after 24 hours, including offshore and eastern-longitude Alaska records. Expired snapshots are never served after a failed refresh; retry or use `bbox`/`station_ids`. Geographic searches retain the stationinfo endpoint and its row cap
- Named lookups also return nullable `magnetic_declination`: signed degrees (east positive) and exact source text from one supplementary airport batch. Unrecognized syntax keeps the text with unknown degrees. Missing airport data and area searches return null; a failed supplementary request adds a notice while preserving station results. This is published variation without an epoch, not a current geomagnetic model or a correction for every PIREP location
---
### `aviation_get_metar` tool
- `station_ids` (1–10 per call — 4 ASCII letters or digits, case-insensitive and normalized to uppercase, so `ksea` and `K0S9` work) for named airports, or `bbox` to survey every reporting station in an area — mutually exclusive
- `hours` (1–12) is a lookback window, not a row limit: with `station_ids` every observation inside it is returned, and with `bbox` the result is the latest observation per station
- `flight_category` (e.g., `["IFR", "LIFR"]`) narrows a `bbox` survey to the stations in those categories — judged on each station's latest observation, applied before `limit`, and disclosed with the count surveyed before it; a station AWC could not rate never matches, and a survey the filter empties returns an empty result that says so. Rejected alongside `station_ids`
- A `bbox` survey states whether the upstream 400-row cap cut it and, above `hours: 1`, names `hours` as the first lever — a wide window spends the cap on repeat readings rather than on more stations; `limit` (1–400) bounds how many stations come back, ordered by station ID ascending, and is rejected alongside `station_ids`. A survey returning more than 40 stations with no `limit` says so and names the levers; omitting `limit` still returns every station
- Flight category (VFR/MVFR/IFR/LIFR) returned directly from the AWC API; decodes wind, visibility, present weather, and cloud layers alongside the raw METAR string
- Ceiling reports both height and kind (measured, or indefinite for vertical visibility into an obscuration) — `sky_condition` distinguishes a reported clear sky from an unreported one when `clouds` is empty
- `metar_type` distinguishes routine `METAR` from special `SPECI` observations
- Every batch reports which requested stations came back, naming missing IDs with recovery guidance
---
### `aviation_get_taf` tool
- Accepts 1–4 ICAO station IDs per call: 4 ASCII letters or digits in either case, normalized to uppercase
- Structured forecast periods with change types (`FM`, `TEMPO`, `BECMG`) and probabilities; weather decoded group by group beside the raw groups
- Forecast obscurations keep their layer and carry the vertical visibility into them, rather than reading as clear sky; `sky_condition` distinguishes an unamended period from a stated clear sky
- Text the upstream decoder left undecoded — often a fourth cloud layer — is surfaced per period in `not_decoded` rather than dropped
- Low-level wind shear (`WS020/20040KT`) decoded to the shear-layer top and forecast wind at that height
- `valid_from` / `valid_to` in ISO 8601 for time comparisons
- Every batch reports which requested stations came back, naming missing IDs with recovery guidance
---
### `aviation_get_pireps` tool
- `station_id` (4 ASCII letters or digits in either case, normalized to uppercase) + `distance_nm` (10–500 nm, 100 when omitted) for radial search, or `bbox` for area search — mutually exclusive; a `station_id` AWC does not recognize as a search center returns a typed error pointing to `aviation_find_stations` or `bbox`
- Resolved station searches select a true nautical-mile circle from enclosing candidates, splitting antimeridian envelopes into two draws. Missing coordinates or an unavailable coordinate lookup retain the legacy AWC search with an explicit unverified-radius notice; use `bbox` for explicit geographic bounds
- `altitude_min_ft` / `altitude_max_ft` filter to a cruise-altitude band in feet MSL, from 0 to 60000 ft (min must not exceed max); a report with unknown altitude is dropped once either bound is set
- `min_intensity` (`lgt` / `mod` / `sev`) restricts to reports carrying a turbulence or icing layer at that intensity or above — a matching report still carries its lighter layers
- Turbulence and icing arrays include up to two layers per report; icing layers the API synthesized for a report that never mentioned ice are dropped
- Source report types remain open strings, including `PIREP`, `Urgent PIREP`, `AIREP`, and `AMDAR`. Outside air temperature (`temp_c`), wind aloft (`wind`), and decoded `/WX` flight weather (`weather`) preserve available readings. Ordinary and urgent PIREP wind directions are magnetic and unconverted; other report types receive no unverified reference label
- Nullable `braking_action` preserves AWC's decoded `brkAction` (e.g., `MED`), including unfamiliar codes, without parsing remarks or inferring runway conditions
- Every result states whether any candidate draw reached the upstream 400-row cap before radius and altitude filtering. Capped draws remain partial even when filtering leaves no reports. `limit` (1–400) selects the most recent matches independently of that cap. A result of more than 50 reports with no `limit` names the lever; omitting `limit` still returns every match
- PIREPs are sparse by nature — absence of reports does not mean smooth conditions
---
### `aviation_get_advisories` tool
- `advisory_type`: `sigmet` (domestic), `isigmet` (international, including oceanic), `cwa` (Center Weather Advisories), or `all` (default: all three independent products)
- `hazard` is applied upstream: `TS` and `CONVECTIVE` are thunderstorm aliases for every product. Domestic also supports `TURBULENCE`, `ICING`, `IFR`; international also supports `TURBULENCE`, `ICING`, `MTW`, `DS`, `SS`, `TC`, `VA`; CWA also supports `TURBULENCE`, `ICING`, `IFR`, `PCPN`, `UNK`. Output hazards stay source-native. Incompatible sources are `not_applicable`; a selection with no compatible source is rejected
- `coverage` reports each selected source as `ok`, `failed` or `not_applicable`, with decoded drawn counts only for readable sources. `partial` marks failed sources or skipped unreadable rows. Independent healthy products survive a failure; all applicable products failing is an error. One 45-second deadline bounds the concurrent advisory reads and retries; caller cancellation aborts all legs
- `altitude_ft` optionally selects a cruise altitude in nonnegative finite feet MSL. It rounds to the nearest 100 ft (half steps upward) and echoes `altitude_selection`: requested feet, effective integer flight level, and ±3,000 ft band with lower edge clamped to zero. SIGMET products use AWC's documented `level`; CWA uses inclusive interval overlap locally. Either unknown CWA bound retains the row conservatively. Per-source `altitude_filter` identifies `upstream` or `client`; `altitude_unknown` counts retained unknown bounds before bbox, describing only returned upstream data, not proven altitude matches. Both are null without an altitude filter or available coverage
- CWA cancellation notices are excluded before active counts; `coverage[].cancelled` discloses their number (zero on readable feeds with none, null when unavailable). Cancellation and unknown altitude alone do not make coverage partial
- `bbox` uses each intact geometry part's bounding envelope, including date-line crossings, rather than exact polygon intersection. Finite extended source longitudes wrap into [-180,180]; canonical coordinates remain unchanged. Input remains ordered (`minLat <= maxLat`, `minLon <= maxLon`). With bbox, `drawn` counts rows after cancellation removal and product/hazard/altitude selection, `matched` counts geographic matches, `returned` counts rows after any limit, and `unlocated` separately counts rows without decoded geometry
- `limit` is optional with no default: omitted means every available match. An explicit limit orders by source, issuer, series and validity, reports `total`/`returned`/`truncated`, and explains how to retrieve withheld matches by omitting or raising it
- Missing issuer, series, hazard, validity and raw text stay null. `geometry.parts` preserves separate rings/lines and source-native `kind` (including null); compatibility `polygon` is null for multipart, line or missing geometry. Domestic numeric severity/movement stay source-native; finite primary altitude bounds precede alternate bounds. International movement preserves `direction_text` (including `-`) and decoded knots on one line; nullable `stationary` is true only for explicit unquoted standalone `STNR`, false for a non-sentinel direction with positive speed, otherwise null. International `tendency` and CWA `issued_by_name` retain source tokens/names or null. CWA severity/movement remain null, and altitudes are never inferred from bulletin text
- Original bulletins render in safe code fences preserving blank lines and embedded backticks. An empty result names readable sources and filtering stage; unavailable sources never establish fair weather
- AIRMETs are not served. Requests for one (or `MTN OBSCN` / `SURFACE WIND` / `LLWS`) are rejected with guidance to separate AIRMET products
---
### `aviation_preflight_brief` prompt
- Arguments: `departure_icao` and `destination_icao` required; `alternates` (comma-separated ICAOs), `departure_time` (ISO 8601 UTC), `cruise_altitude` (feet MSL), and `route_waypoints` (semicolon-separated `lat,lon` pairs) optional
- Every ICAO argument accepts 4 ASCII letters or digits in either case and generates uppercase IDs. For an IATA/FAA code, use `aviation_find_stations` with `state` or `bbox` to find the ICAO ID; no mapping is inferred. Direct IDs reject surrounding whitespace; comma-separated alternates allow it
- Calls `aviation_get_metar`, `aviation_get_taf`, `aviation_get_pireps`, and `aviation_get_advisories` in sequence, chunked to each tool's station-per-call limit
- `departure_time` selects the TAF forecast period the briefing is read against; `cruise_altitude` bounds the PIREP search to a ±3,000 ft band and forwards `altitude_ft` to advisories, including explicit zero; `route_waypoints` become the advisories `bbox`, widened by 1° on each side and retained alongside altitude selection
- Omitting any of the three still generates the briefing, naming the assessment it could not make
- Reports weather risk rather than a go/no-go recommendation — that decision needs pilot, aircraft, and operational-minima context this server does not hold
---
## Features
Built on [`@cyanheads/mcp-ts-core`](https://github.com/cyanheads/mcp-ts-core): stdio and Streamable HTTP transports, pluggable auth (`none` / `jwt` / `oauth`), swappable storage (`in-memory`, `filesystem`, `Supabase`, `Cloudflare KV/R2/D1`), structured logging with optional OpenTelemetry tracing.
Aviation-weather-specific:
- Keyless — no API key or authentication required; all data is from the public AWC Data API
- Single service (`aviation-weather-service`) with retry + exponential backoff for the keyless public endpoint
- Raw coded strings (`raw_metar`, `raw_taf`, `raw_pirep`, `raw_text`) surfaced alongside decoded fields so agents have both layers
- Complete in-memory station registry snapshots provide US-state membership without geographic approximations
- Server-level `instructions` field surfaces the "not an official briefing" safety disclaimer to all clients on `initialize`
Agent-friendly output:
- Discriminated output — flight category (`VFR`/`MVFR`/`IFR`/`LIFR`) as a typed string field, so agents branch on it without parsing ceiling and visibility
- Structured error contracts — typed `reason` fields with `recovery` hints (e.g., "Verify ICAO IDs with `aviation_find_stations`")
- Partial-result reconciliation — batch tools report `requested` / `returned` / `missing` / `partial` fields, so a short batch is never mistaken for full coverage
- Workflow sequencing — the `aviation_preflight_brief` prompt encodes the correct METAR → TAF → PIREPs → advisories sequence, chunks each step to the tool's station limit, and names the assessments it could not make
---
## Getting started
### Public Hosted Instance
A public hosted instance is available at `https://aviation-weather.caseyjhand.com/mcp`. Add it to your MCP client configuration:
```json
{
"mcpServers": {
"aviation-weather": {
"type": "streamable-http",
"url": "https://aviation-weather.caseyjhand.com/mcp"
}
}
}
```
### Self-Hosted / Local
Add the following to your MCP client configuration file.
```json
{
"mcpServers": {
"aviation-weather": {
"type": "stdio",
"command": "bunx",
"args": ["@cyanheads/aviation-weather-mcp-server@latest"],
"env": {
"MCP_TRANSPORT_TYPE": "stdio",
"MCP_LOG_LEVEL": "info"
}
}
}
}
```
Or with npx (no Bun required):
```json
{
"mcpServers": {
"aviation-weather": {
"type": "stdio",
"command": "npx",
"args": ["-y", "@cyanheads/aviation-weather-mcp-server@latest"],
"env": {
"MCP_TRANSPORT_TYPE": "stdio",
"MCP_LOG_LEVEL": "info"
}
}
}
}
```
Or with Docker:
```json
{
"mcpServers": {
"aviation-weather": {
"type": "stdio",
"command": "docker",
"args": [
"run", "-i", "--rm",
"-e", "MCP_TRANSPORT_TYPE=stdio",
"ghcr.io/cyanheads/aviation-weather-mcp-server:latest"
]
}
}
}
```
For Streamable HTTP, set the transport and start the server:
```sh
MCP_TRANSPORT_TYPE=http MCP_HTTP_PORT=3010 bun run start:http
# Server listens at http://localhost:3010/mcp
```
### Prerequisites
- [Bun v1.4.0](https://bun.sh/) or higher (or Node.js v24+).
- No API key required — the AWC Data API is fully public and keyless.
### Installation
1. **Clone the repository:**
```sh
git clone https://github.com/cyanheads/aviation-weather-mcp-server.git
```
2. **Navigate into the directory:**
```sh
cd aviation-weather-mcp-server
```
3. **Install dependencies:**
```sh
bun install
```
4. **Configure environment:**
```sh
cp .env.example .env
# edit .env if you need to override AWC_BASE_URL or AWC_TIMEOUT_MS
```
---
## Configuration
| Variable | Description | Default |
|:---------|:------------|:--------|
| `AWC_BASE_URL` | Base URL for the NWS AWC Data API. | `https://aviationweather.gov/api/data` |
| `AWC_TIMEOUT_MS` | Per-request timeout in milliseconds (1000–60000). | `10000` |
| `MCP_TRANSPORT_TYPE` | Transport: `stdio` or `http`. | `stdio` |
| `MCP_HTTP_PORT` | Port for HTTP server. | `3010` |
| `MCP_SESSION_MODE` | HTTP session handling: `auto` (resolves to `stateful`), `stateful`, or `stateless`. The server declares `stateless` in code — no tool here needs a multi-round-trip input — and the shipped `.env.example` and Docker image pin the same value. Setting this overrides the declaration. | `stateless` |
| `MCP_AUTH_MODE` | Auth mode: `none`, `jwt`, or `oauth`. | `none` |
| `MCP_LOG_LEVEL` | Log level (RFC 5424). | `info` |
| `OTEL_ENABLED` | Enable [OpenTelemetry instrumentation](https://github.com/cyanheads/mcp-ts-core/tree/main/docs/telemetry). | `false` |
See [`.env.example`](./.env.example) for the full list of optional overrides.
---
## Running the server
### Local development
- **Build and run:**
```sh
bun run rebuild
bun run start:stdio
# or
bun run start:http
```
- **Run checks and tests:**
```sh
bun run devcheck # Lint, format, typecheck, security
bun run test # Vitest test suite
bun run lint:mcp # Validate MCP definitions against spec
```
### Docker
```sh
docker build -t aviation-weather-mcp-server .
docker run --rm -p 3010:3010 aviation-weather-mcp-server
```
The Dockerfile defaults to HTTP transport, stateless session mode, and logs to `/var/log/aviation-weather-mcp-server`. OpenTelemetry peer dependencies are installed by default — build with `--build-arg OTEL_ENABLED=false` to omit them.
---
## Project structure
| Directory | Purpose |
|:----------|:--------|
| `src/index.ts` | `createApp()` entry point — registers tools/prompts and inits services. |
| `src/config` | Server-specific env var parsing (`AWC_BASE_URL`, `AWC_TIMEOUT_MS`). |
| `src/services/aviation-weather` | AWC Data API client — HTTP fetch, retry with exponential backoff, response normalization. |
| `src/mcp-server/tools` | Tool definitions (`*.tool.ts`). |
| `src/mcp-server/prompts` | Prompt definitions (`*.prompt.ts`). |
| `skills/aviation-weather-guide` | Published assessment guide, available through MCP as `skill://aviation-weather-guide/SKILL.md` and discovered by plugin hosts. |
| `tests/` | Unit and integration tests mirroring `src/`. |
---
## Development guide
See [`CLAUDE.md`](./CLAUDE.md) for development guidelines and architectural rules. The short version:
- Handlers throw, framework catches — no `try/catch` in tool logic
- Use `ctx.log` for request-scoped logging, `ctx.state` for tenant-scoped storage
- Register new tools and prompts in the `createApp()` arrays in `src/index.ts`
- Wrap external API calls: validate raw → normalize to domain type → return output schema; never fabricate missing fields
> **Not an official preflight briefing.** Data from the AWC is informational only. Real flight planning requires an authorized source (e.g., Leidos/1800wxbrief.com). The server surfaces this disclaimer via its `instructions` field sent on every `initialize`.
---
## Contributing
Issues are welcome. Run checks and tests before submitting:
```sh
bun run devcheck
bun run test
```
---
## License
Apache-2.0 — see [LICENSE](LICENSE) for details.