feat(weather): /weather-ca endpoint shows HRDPS-only Canadian data

New LiveView at /weather-ca duplicates the /weather UI but defaults the
viewport to central Canada (55N, -100W, z=4) and renders the map div
with data-source="hrdps". The JS hook reads that attribute and appends
&source=hrdps to every cell fetch; the WeatherTileController routes
those reads through Weather.weather_grid_hrdps_at/2, which only reads
the <vt>.hrdps scalar dir and skips HRRR merging entirely. Timeline is
sourced from ScalarFile.list_valid_times_hrdps/0 so HRDPS-only hours
show up even when no HRRR file exists for the same valid_time.

Also drops "— Unified" from the algo.md H1.

algo.md

@@ -1,4 +1,4 @@
-# Microwave Propagation Algorithm — Unified
+# Microwave Propagation Algorithm
 
 ## Overview
 

assets/js/weather_map_hook.ts

@@ -81,6 +81,7 @@ interface WeatherMapHook extends ViewHook {
   map: L.Map
   weatherOverlay: WeatherCanvasOverlay | null
   weatherCellsUrl: string
+  source: string | null
   selectedLayer: LayerId
   pack: CellPack | null
   packKey: string | null
@@ -678,6 +679,7 @@ export const WeatherMap: WeatherMapHook = {
 
     this.weatherOverlay = null
     this.weatherCellsUrl = "/weather/cells"
+    this.source = this.el.dataset.source || null
     this.selectedLayer = (this.el.dataset.selectedLayer || "temperature") as LayerId
     this.pack = null
     this.packKey = null
@@ -990,10 +992,12 @@ export const WeatherMap: WeatherMapHook = {
     if (cacheKey !== this.packKey) return
 
     const { south, north, west, east } = quantizeBounds(this.map.getBounds())
+    const sourceQuery = this.source ? `&source=${encodeURIComponent(this.source)}` : ""
     const url =
       `${this.weatherCellsUrl}?format=bin&time=${encodeURIComponent(this.selectedTime)}` +
       `&south=${south}&north=${north}&west=${west}&east=${east}` +
-      `&layers=${layers.join(",")}`
+      `&layers=${layers.join(",")}` +
+      sourceQuery
 
     const abort = new AbortController()
     if (layers.length === 1 || !this.pack) this.inflightCellsAbort = abort

lib/microwaveprop/weather.ex

@@ -917,6 +917,28 @@ defmodule Microwaveprop.Weather do
     |> Enum.sort(DateTime)
   end
 
+  @doc """
+  All persisted HRDPS valid_times (i.e. those with a `<iso>.hrdps`
+  scalar dir on disk) sorted ascending. Backs the `/weather-ca`
+  timeline.
+  """
+  @spec available_hrdps_valid_times() :: [DateTime.t()]
+  def available_hrdps_valid_times do
+    ScalarFile.list_valid_times_hrdps()
+  end
+
+  @doc """
+  HRDPS-only counterpart to `weather_grid_at/2`. Reads from the
+  `<vt>.hrdps` scalar dir and skips HRRR completely. Bypasses GridCache
+  because the cache mixes HRRR + HRDPS rows by design — caching this
+  separately would double the per-pod memory budget for marginal benefit
+  (Canadian viewport reads are infrequent compared to CONUS).
+  """
+  @spec weather_grid_hrdps_at(DateTime.t(), %{optional(String.t()) => float()} | nil) :: [map()]
+  def weather_grid_hrdps_at(%DateTime{} = valid_time, bounds) do
+    ScalarFile.read_bounds_hrdps(valid_time, bounds)
+  end
+
   @doc """
   Read the weather grid for a specific `valid_time` and bounds. Like
   `load_weather_grid/1` but takes the valid_time explicitly so the

lib/microwaveprop/weather/scalar_file.ex

@@ -179,6 +179,18 @@ defmodule Microwaveprop.Weather.ScalarFile do
     end
   end
 
+  @doc """
+  Read only the HRDPS sibling chunks for `valid_time` whose lat/lon falls
+  within `bounds`. Used by the `/weather-ca` endpoint, which intentionally
+  excludes HRRR-derived rows so the user can see Canadian-source data
+  without being eclipsed by the higher-resolution HRRR scalars over the
+  US/Canada border.
+  """
+  @spec read_bounds_hrdps(DateTime.t(), bounds() | nil) :: [row()]
+  def read_bounds_hrdps(%DateTime{} = valid_time, bounds) do
+    read_chunks(list_chunk_files_hrdps(valid_time), bounds)
+  end
+
   defp read_chunks([], _bounds), do: []
 
   defp read_chunks(files, bounds) do
@@ -263,6 +275,30 @@ defmodule Microwaveprop.Weather.ScalarFile do
     end
   end
 
+  @doc """
+  Like `list_valid_times/0` but returns only the valid_times that have a
+  `<iso>.hrdps` directory present. Backs the `/weather-ca` timeline so
+  the scrubber surfaces HRDPS-only hours that wouldn't otherwise appear
+  on the standard `/weather` timeline.
+  """
+  @spec list_valid_times_hrdps() :: [DateTime.t()]
+  def list_valid_times_hrdps do
+    case File.ls(base_dir()) do
+      {:ok, entries} ->
+        times =
+          for entry <- entries,
+              String.ends_with?(entry, ".hrdps"),
+              iso = String.trim_trailing(entry, ".hrdps"),
+              {:ok, dt, _} <- [DateTime.from_iso8601(iso)],
+              do: dt
+
+        Enum.sort(times, DateTime)
+
+      _ ->
+        []
+    end
+  end
+
   @doc "Delete scalar dirs whose valid_time is strictly before `cutoff`. Returns count removed."
   @spec prune_older_than(DateTime.t()) :: non_neg_integer()
   def prune_older_than(%DateTime{} = cutoff) do

lib/microwaveprop_web/controllers/weather_tile_controller.ex

@@ -18,7 +18,7 @@ defmodule MicrowavepropWeb.WeatherTileController do
     with {:ok, valid_time, _offset} <- DateTime.from_iso8601(time_param),
          {:ok, bounds} <- parse_bounds(params),
          {:ok, layers} <- parse_layers(params["layers"]) do
-      rows = Weather.weather_grid_at(valid_time, bounds)
+      rows = read_rows(valid_time, bounds, params["source"])
 
       conn
       |> put_resp_header("content-type", "application/octet-stream")
@@ -31,6 +31,9 @@ defmodule MicrowavepropWeb.WeatherTileController do
 
   def cells(conn, _params), do: bad_request(conn)
 
+  defp read_rows(valid_time, bounds, "hrdps"), do: Weather.weather_grid_hrdps_at(valid_time, bounds)
+  defp read_rows(valid_time, bounds, _other), do: Weather.weather_grid_at(valid_time, bounds)
+
   defp bad_request(conn) do
     conn
     |> put_status(400)

lib/microwaveprop_web/live/weather_ca_map_live.ex

@@ -0,0 +1,600 @@
+defmodule MicrowavepropWeb.WeatherCaMapLive do
+  @moduledoc """
+  `/weather-ca` — sibling of `/weather` that shows ONLY HRDPS-derived
+  Canadian fields. Same UI, same JS hook, same layer set — but the cell
+  fetch is filtered to `source=hrdps` and the timeline is sourced from
+  `<vt>.hrdps` scalar dirs only. Defaults the viewport to central Canada.
+  """
+  use MicrowavepropWeb, :live_view
+
+  alias Microwaveprop.Weather
+  alias Microwaveprop.Weather.MapLayers
+
+  @layers MapLayers.all()
+  @default_layer MapLayers.default_id()
+
+  # Default map viewport — central Canada at z=4 so the user lands on
+  # the HRDPS coverage area, not DFW.
+  @default_center_lat 55.0
+  @default_center_lon -100.0
+  @default_zoom 4
+  @min_zoom 4
+  @max_zoom 10
+
+  @impl true
+  def mount(params, _session, socket) do
+    _ =
+      if connected?(socket) do
+        :ok = Phoenix.PubSub.subscribe(Microwaveprop.PubSub, "weather:updated")
+        Phoenix.PubSub.subscribe(Microwaveprop.PubSub, "propagation:pipeline")
+      end
+
+    valid_times = recent_valid_times(Weather.available_hrdps_valid_times())
+    initial_vt = pick_initial_valid_time(valid_times)
+
+    {lat, lon, zoom} = parse_viewport_params(params)
+
+    {:ok,
+     assign(socket,
+       page_title: "Canadian Weather Map",
+       layers: @layers,
+       selected_layer: @default_layer,
+       valid_time: initial_vt,
+       valid_times: valid_times,
+       initial_valid_times_json: Jason.encode!(Enum.map(valid_times, &DateTime.to_iso8601/1)),
+       initial_selected_time: initial_vt && DateTime.to_iso8601(initial_vt),
+       initial_utc_clock: Calendar.strftime(DateTime.utc_now(), "%H:%M UTC"),
+       initial_center_lat: lat,
+       initial_center_lon: lon,
+       initial_zoom: zoom,
+       current_lat: lat,
+       current_lon: lon,
+       current_zoom: zoom,
+       grid_visible: false,
+       radar_visible: false
+     )}
+  end
+
+  @impl true
+  def handle_params(params, _uri, socket) do
+    selected = pick_layer(params["layer"], socket.assigns[:selected_layer])
+    {lat, lon, zoom} = parse_viewport_params(params)
+
+    {:noreply,
+     socket
+     |> assign(:selected_layer, selected)
+     |> assign(:current_lat, lat)
+     |> assign(:current_lon, lon)
+     |> assign(:current_zoom, zoom)}
+  end
+
+  defp pick_layer(layer, current) when is_binary(layer) do
+    if MapLayers.valid_id?(layer), do: layer, else: pick_layer(nil, current)
+  end
+
+  defp pick_layer(_layer, current) when is_binary(current), do: current
+  defp pick_layer(_layer, _current), do: @default_layer
+
+  defp parse_viewport_params(params) do
+    lat = parse_float_param(params["lat"], -90.0, 90.0, @default_center_lat)
+    lon = parse_float_param(params["lon"], -180.0, 180.0, @default_center_lon)
+
+    zoom =
+      case Integer.parse(params["zoom"] || "") do
+        {z, ""} when z >= @min_zoom and z <= @max_zoom -> z
+        _ -> @default_zoom
+      end
+
+    {lat, lon, zoom}
+  end
+
+  defp parse_float_param(value, min, max, default) when is_binary(value) do
+    case Float.parse(value) do
+      {f, ""} when f >= min and f <= max -> f
+      _ -> default
+    end
+  end
+
+  defp parse_float_param(_value, _min, _max, default), do: default
+
+  defp pick_initial_valid_time([]), do: nil
+
+  defp pick_initial_valid_time(valid_times) do
+    now = DateTime.utc_now()
+    Enum.min_by(valid_times, fn vt -> abs(DateTime.diff(vt, now, :second)) end)
+  end
+
+  # Drop valid_times older than one hour. HRDPS cycles run 4×/day and
+  # the chain seeder writes one row per hour, so the on-disk set can
+  # span many old hours; the user wants "now", not yesterday.
+  defp recent_valid_times(valid_times) do
+    cutoff = DateTime.add(DateTime.utc_now(), -3600, :second)
+    Enum.filter(valid_times, fn vt -> DateTime.compare(vt, cutoff) != :lt end)
+  end
+
+  defp build_path(socket, overrides \\ []) do
+    layer = Keyword.get(overrides, :layer, socket.assigns.selected_layer)
+    lat = Keyword.get(overrides, :lat, socket.assigns.current_lat)
+    lon = Keyword.get(overrides, :lon, socket.assigns.current_lon)
+    zoom = Keyword.get(overrides, :zoom, socket.assigns.current_zoom)
+
+    query =
+      URI.encode_query([
+        {"layer", layer},
+        {"lat", lat},
+        {"lon", lon},
+        {"zoom", zoom}
+      ])
+
+    "/weather-ca?#{query}"
+  end
+
+  @impl true
+  def handle_event("select_layer", %{"layer" => layer_id}, socket) do
+    if MapLayers.valid_id?(layer_id) do
+      {:noreply, push_patch(socket, to: build_path(socket, layer: layer_id))}
+    else
+      {:noreply, socket}
+    end
+  end
+
+  def handle_event("viewport_changed", %{"lat" => lat, "lon" => lon, "zoom" => zoom}, socket)
+      when is_number(lat) and is_number(lon) and is_number(zoom) do
+    new_lat = lat |> max(-90.0) |> min(90.0) |> Float.round(4)
+    new_lon = lon |> max(-180.0) |> min(180.0) |> Float.round(4)
+    new_zoom = zoom |> max(@min_zoom) |> min(@max_zoom) |> trunc()
+
+    socket =
+      socket
+      |> assign(:current_lat, new_lat)
+      |> assign(:current_lon, new_lon)
+      |> assign(:current_zoom, new_zoom)
+
+    {:noreply, push_patch(socket, to: build_path(socket), replace: true)}
+  end
+
+  def handle_event("viewport_changed", _params, socket), do: {:noreply, socket}
+
+  def handle_event("toggle_grid", _params, socket) do
+    visible = !socket.assigns.grid_visible
+
+    socket =
+      socket
+      |> assign(:grid_visible, visible)
+      |> push_event("toggle_grid", %{visible: visible})
+
+    {:noreply, socket}
+  end
+
+  def handle_event("toggle_radar", _params, socket) do
+    visible = !socket.assigns.radar_visible
+
+    socket =
+      socket
+      |> assign(:radar_visible, visible)
+      |> push_event("toggle_radar", %{visible: visible})
+
+    {:noreply, socket}
+  end
+
+  def handle_event("select_time", %{"time" => time_str}, socket) do
+    with {:ok, time, _} <- DateTime.from_iso8601(time_str),
+         true <- time in socket.assigns.valid_times do
+      socket =
+        socket
+        |> assign(:valid_time, time)
+        |> push_event("update_weather_overlay", %{selected: DateTime.to_iso8601(time)})
+
+      {:noreply, socket}
+    else
+      _ -> {:noreply, socket}
+    end
+  end
+
+  def handle_event("point_detail", %{"lat" => lat, "lon" => lon}, socket) do
+    detail =
+      if socket.assigns.valid_time do
+        Weather.weather_point_detail(lat, lon, socket.assigns.valid_time)
+      end
+
+    payload = detail || %{}
+    {:noreply, push_event(socket, "point_detail", payload)}
+  end
+
+  @impl true
+  def handle_info({:weather_updated, _valid_time}, socket) do
+    valid_times = recent_valid_times(Weather.available_hrdps_valid_times())
+
+    selected =
+      cond do
+        socket.assigns.valid_time in valid_times -> socket.assigns.valid_time
+        valid_times != [] -> List.last(valid_times)
+        true -> nil
+      end
+
+    socket =
+      socket
+      |> assign(:valid_times, valid_times)
+      |> assign(:valid_time, selected)
+      |> push_event("update_weather_overlay", %{selected: selected && DateTime.to_iso8601(selected)})
+      |> push_event("update_timeline", %{
+        times: Enum.map(valid_times, &DateTime.to_iso8601/1),
+        selected: selected && DateTime.to_iso8601(selected)
+      })
+
+    {:noreply, socket}
+  end
+
+  def handle_info({:propagation_pipeline_progress, _progress}, socket) do
+    valid_times = recent_valid_times(Weather.available_hrdps_valid_times())
+
+    if valid_times == socket.assigns.valid_times do
+      {:noreply, socket}
+    else
+      socket =
+        socket
+        |> assign(:valid_times, valid_times)
+        |> push_event("update_timeline", %{
+          times: Enum.map(valid_times, &DateTime.to_iso8601/1),
+          selected: socket.assigns.valid_time && DateTime.to_iso8601(socket.assigns.valid_time)
+        })
+
+      {:noreply, socket}
+    end
+  end
+
+  @group_order ["Surface", "Upper Air", "Ducting"]
+
+  defp group_layers(layers) do
+    layers
+    |> Enum.group_by(& &1.group)
+    |> Enum.sort_by(fn {group, _} -> Enum.find_index(@group_order, &(&1 == group)) || 99 end)
+  end
+
+  defp layer_description(layers, selected_id) do
+    case Enum.find(layers, &(&1.id == selected_id)) do
+      %{desc: desc} -> desc
+      _ -> nil
+    end
+  end
+
+  defp selected_layer_label(layers, selected_id) do
+    case Enum.find(layers, &(&1.id == selected_id)) do
+      %{label: label} -> label
+      _ -> ""
+    end
+  end
+
+  defp selected_layer_group_label(layers, selected_id) do
+    case Enum.find(layers, &(&1.id == selected_id)) do
+      %{group: group} -> group
+      _ -> ""
+    end
+  end
+
+  @impl true
+  def render(assigns) do
+    ~H"""
+    <div class="flex w-screen h-screen overflow-hidden">
+      <div class="relative flex-1 min-w-0">
+        <div
+          id="weather-map"
+          phx-hook="WeatherMap"
+          phx-update="ignore"
+          data-layers={Jason.encode!(@layers)}
+          data-selected-layer={@selected_layer}
+          data-valid-times={@initial_valid_times_json}
+          data-selected-time={@initial_selected_time}
+          data-initial-lat={@initial_center_lat}
+          data-initial-lon={@initial_center_lon}
+          data-initial-zoom={@initial_zoom}
+          data-source="hrdps"
+          class="absolute inset-0 z-0"
+        >
+        </div>
+
+        <div
+          id="weather-forecast-timeline"
+          phx-update="ignore"
+          class="absolute bottom-2 left-1/2 -translate-x-1/2 z-[1000] max-w-[calc(100vw-1rem)] md:bottom-4"
+        >
+        </div>
+
+        <div
+          id="weather-controls"
+          class="md:hidden absolute top-2 left-12 z-[1000] flex flex-col gap-2 max-w-[calc(100vw-4rem)]"
+        >
+          <div
+            data-theme="dark"
+            class="bg-neutral text-neutral-content shadow rounded-box border border-base-300 p-2 flex flex-col gap-2"
+          >
+            <div class="font-bold text-sm leading-tight px-1 flex items-center justify-between gap-2">
+              <div class="min-w-0">
+                <span>NTMS</span>
+                <div class="font-normal text-xs opacity-70">Canadian Weather Map</div>
+                <div class="font-normal text-[10px] opacity-60">
+                  <%= if @valid_time do %>
+                    {Calendar.strftime(@valid_time, "%Y-%m-%d %H:%M UTC")}
+                  <% else %>
+                    No data available
+                  <% end %>
+                </div>
+              </div>
+              <div class="flex items-center gap-1.5 shrink-0">
+                <div
+                  id="weather-utc-clock-mobile"
+                  phx-hook="UtcClock"
+                  phx-update="ignore"
+                  class="font-mono text-xs opacity-70 tabular-nums"
+                >
+                  {@initial_utc_clock}
+                </div>
+                <button
+                  id="weather-mobile-panel-toggle"
+                  class="btn btn-xs btn-square btn-ghost"
+                  onclick="document.getElementById('weather-panel-extras').classList.toggle('hidden')"
+                >
+                  <.icon name="hero-bars-3" class="size-4" />
+                </button>
+              </div>
+            </div>
+
+            <div id="weather-panel-extras" class="hidden flex-col gap-2">
+              <div class="flex flex-col gap-1.5">
+                <div :for={{group, layers} <- group_layers(@layers)}>
+                  <div class="text-[10px] font-semibold opacity-50 uppercase tracking-wider px-1 mb-0.5">
+                    {group}
+                  </div>
+                  <div class="flex flex-wrap gap-1">
+                    <button
+                      :for={layer <- layers}
+                      phx-click="select_layer"
+                      phx-value-layer={layer.id}
+                      class={[
+                        "btn btn-xs rounded-full",
+                        if(@selected_layer == layer.id, do: "btn-primary", else: "btn-ghost")
+                      ]}
+                    >
+                      {layer.label}
+                    </button>
+                  </div>
+                </div>
+              </div>
+
+              <div class="text-[11px] opacity-70 px-1 leading-snug">
+                {layer_description(@layers, @selected_layer)}
+              </div>
+
+              <div class="flex flex-col gap-1 border-t border-base-300 pt-2">
+                <label class="flex items-center gap-2 cursor-pointer px-1">
+                  <input
+                    type="checkbox"
+                    class="toggle toggle-sm toggle-primary"
+                    checked={@grid_visible}
+                    phx-click="toggle_grid"
+                  />
+                  <span class="text-sm">Grid squares</span>
+                </label>
+                <label class="flex items-center gap-2 cursor-pointer px-1">
+                  <input
+                    type="checkbox"
+                    class="toggle toggle-sm toggle-primary"
+                    checked={@radar_visible}
+                    phx-click="toggle_radar"
+                  />
+                  <span class="text-sm">Weather radar</span>
+                </label>
+              </div>
+
+              <div class="flex flex-col gap-1 border-t border-base-300 pt-2">
+                <.link navigate="/weather" class="btn btn-xs btn-ghost justify-start">
+                  US Weather Map
+                </.link>
+                <.link navigate="/map" class="btn btn-xs btn-ghost justify-start">
+                  Propagation Map
+                </.link>
+                <.link navigate="/path" class="btn btn-xs btn-ghost justify-start">
+                  Path Calculator
+                </.link>
+                <.link navigate="/eme" class="btn btn-xs btn-ghost justify-start">
+                  EME
+                </.link>
+                <.link navigate="/beacons" class="btn btn-xs btn-ghost justify-start">
+                  Beacons
+                </.link>
+                <.link navigate="/submit" class="btn btn-xs btn-ghost justify-start">
+                  Submit a Contact
+                </.link>
+                <.link navigate="/contacts" class="btn btn-xs btn-ghost justify-start">
+                  Contact Training Data
+                </.link>
+                <.link navigate="/contacts/map" class="btn btn-xs btn-ghost justify-start">
+                  Contact Map
+                </.link>
+                <.link navigate="/algo" class="btn btn-xs btn-ghost justify-start">
+                  Scoring Algorithm
+                </.link>
+                <.link navigate="/about" class="btn btn-xs btn-ghost justify-start">
+                  About
+                </.link>
+              </div>
+            </div>
+          </div>
+        </div>
+
+        <div
+          id="weather-detail-panel"
+          phx-update="ignore"
+          class={[
+            "bg-neutral text-neutral-content shadow-lg border border-base-300 overflow-hidden overflow-y-auto z-[1001]",
+            "fixed bottom-0 left-0 right-0 max-h-[50vh] rounded-t-2xl",
+            "md:absolute md:top-auto md:right-auto md:bottom-4 md:left-3 md:max-h-[70vh] md:w-80 md:rounded-box"
+          ]}
+          style="display:none;"
+        >
+        </div>
+
+        <button
+          id="weather-sidebar-expand"
+          class="hidden md:hidden absolute top-3 right-3 z-[1000] btn btn-sm btn-neutral shadow-lg"
+          onclick="document.getElementById('weather-sidebar').style.display='flex';this.style.display='none';window.dispatchEvent(new Event('sidebar-toggle'));"
+        >
+          <.icon name="hero-bars-3" class="size-4" />
+        </button>
+      </div>
+
+      <div
+        id="weather-sidebar"
+        data-theme="dark"
+        class="hidden md:flex flex-col w-56 shrink-0 h-full bg-neutral text-neutral-content border-l border-base-300 overflow-hidden"
+      >
+        <div class="p-3 flex flex-col gap-2 shrink-0 overflow-y-auto flex-1">
+          <div class="font-bold text-sm leading-tight px-1 flex items-center justify-between gap-2">
+            <div class="min-w-0">
+              <span>NTMS</span>
+              <div class="font-normal text-xs opacity-70">Canadian Weather Map</div>
+              <div class="font-normal text-[10px] opacity-60">
+                <%= if @valid_time do %>
+                  {Calendar.strftime(@valid_time, "%Y-%m-%d %H:%M UTC")}
+                <% else %>
+                  No data available
+                <% end %>
+              </div>
+            </div>
+            <div class="flex items-center gap-1.5 shrink-0">
+              <div
+                id="weather-utc-clock-desktop"
+                phx-hook="UtcClock"
+                phx-update="ignore"
+                class="font-mono text-xs opacity-70 tabular-nums"
+              >
+                {@initial_utc_clock}
+              </div>
+              <button
+                id="weather-sidebar-collapse"
+                class="btn btn-xs btn-square btn-ghost"
+                title="Collapse sidebar"
+                onclick="document.getElementById('weather-sidebar').style.display='none';document.getElementById('weather-sidebar-expand').style.display='flex';window.dispatchEvent(new Event('sidebar-toggle'));"
+              >
+                <.icon name="hero-chevron-right" class="size-4" />
+              </button>
+            </div>
+          </div>
+
+          <div class="flex flex-col gap-1.5">
+            <div :for={{group, layers} <- group_layers(@layers)}>
+              <div class="text-[10px] font-semibold opacity-50 uppercase tracking-wider px-1 mb-0.5">
+                {group}
+              </div>
+              <div class="flex flex-wrap gap-1">
+                <button
+                  :for={layer <- layers}
+                  phx-click="select_layer"
+                  phx-value-layer={layer.id}
+                  class={[
+                    "btn btn-xs rounded-full",
+                    if(@selected_layer == layer.id, do: "btn-primary", else: "btn-ghost")
+                  ]}
+                >
+                  {layer.label}
+                </button>
+              </div>
+            </div>
+          </div>
+
+          <div class="px-1">
+            <div class="text-[10px] font-semibold uppercase tracking-wider opacity-60 mb-1">
+              {selected_layer_group_label(@layers, @selected_layer)} &middot; {selected_layer_label(
+                @layers,
+                @selected_layer
+              )}
+            </div>
+            <div class="text-[11px] opacity-70 leading-snug">
+              {layer_description(@layers, @selected_layer)}
+            </div>
+          </div>
+
+          <div class="flex flex-col gap-1 border-t border-base-300 pt-2">
+            <label class="flex items-center gap-2 cursor-pointer px-1">
+              <input
+                type="checkbox"
+                class="toggle toggle-sm toggle-primary"
+                checked={@grid_visible}
+                phx-click="toggle_grid"
+              />
+              <span class="text-sm">Grid squares</span>
+            </label>
+            <label class="flex items-center gap-2 cursor-pointer px-1">
+              <input
+                type="checkbox"
+                class="toggle toggle-sm toggle-primary"
+                checked={@radar_visible}
+                phx-click="toggle_radar"
+              />
+              <span class="text-sm">Weather radar</span>
+            </label>
+          </div>
+
+          <ul class="menu menu-xs border-t border-base-300 pt-2 px-0">
+            <li>
+              <.link navigate="/weather">US Weather Map</.link>
+            </li>
+            <li>
+              <.link navigate="/map">Propagation Map</.link>
+            </li>
+            <li>
+              <.link navigate="/path">Path Calculator</.link>
+            </li>
+            <li>
+              <.link navigate="/eme">EME</.link>
+            </li>
+            <li>
+              <.link navigate="/beacons">Beacons</.link>
+            </li>
+            <li>
+              <.link navigate="/submit">Submit a Contact</.link>
+            </li>
+            <li>
+              <.link navigate="/contacts">Contact Training Data</.link>
+            </li>
+            <li>
+              <.link navigate="/contacts/map">Contact Map</.link>
+            </li>
+            <li>
+              <.link navigate="/algo">Scoring Algorithm</.link>
+            </li>
+            <li>
+              <.link navigate="/about">About</.link>
+            </li>
+          </ul>
+
+          <ul class="menu menu-xs border-t border-base-300 pt-2 px-0">
+            <%= if @current_scope && @current_scope.user do %>
+              <li>
+                <.link navigate={~p"/u/#{@current_scope.user.callsign}"} class="font-semibold">
+                  {@current_scope.user.callsign}
+                </.link>
+              </li>
+              <li>
+                <.link href={~p"/users/settings"}>Settings</.link>
+              </li>
+              <li>
+                <.link href={~p"/users/log-out"} method="delete">Log out</.link>
+              </li>
+            <% else %>
+              <li>
+                <.link href={~p"/users/register"}>Register</.link>
+              </li>
+              <li>
+                <.link href={~p"/users/log-in"}>Log in</.link>
+              </li>
+            <% end %>
+          </ul>
+        </div>
+      </div>
+    </div>
+
+    <Layouts.flash_group flash={@flash} />
+    """
+  end
+end

lib/microwaveprop_web/router.ex

@@ -188,6 +188,7 @@ defmodule MicrowavepropWeb.Router do
       live "/imports/:id", ImportLive
       live "/map", MapLive
       live "/weather", WeatherMapLive
+      live "/weather-ca", WeatherCaMapLive
       live "/contacts", ContactLive.Index
       live "/contacts/map", ContactMapLive
       live "/contacts/:id", ContactLive.Show

test/microwaveprop/weather/scalar_file_test.exs

@@ -202,6 +202,50 @@ defmodule Microwaveprop.Weather.ScalarFileTest do
     end
   end
 
+  describe "HRDPS-only reads (for the /weather-ca endpoint)" do
+    test "read_bounds_hrdps returns only HRDPS chunks, ignoring co-located HRRR" do
+      vt = ~U[2026-04-29 12:00:00Z]
+
+      # Both dirs cover the same point. The HRRR-only read_bounds/2 would
+      # merge them (preferring HRRR); read_bounds_hrdps/2 must return ONLY
+      # the HRDPS row so /weather-ca shows Canadian-source data.
+      ScalarFile.write!(vt, [sample_row(33.0, -97.0, 22.0)])
+      hand_write_chunk(ScalarFile.dir_for_hrdps(vt), 53.0, -60.0, 8.0)
+
+      assert [%{lat: 53.0, lon: -60.0, temperature: 8.0}] =
+               ScalarFile.read_bounds_hrdps(vt, nil)
+    end
+
+    test "read_bounds_hrdps respects bounds" do
+      vt = ~U[2026-04-29 12:00:00Z]
+
+      hand_write_chunk(ScalarFile.dir_for_hrdps(vt), 53.0, -60.0, 8.0)
+      hand_write_chunk(ScalarFile.dir_for_hrdps(vt), 33.0, -97.0, 22.0)
+
+      bounds = %{"south" => 50.0, "north" => 60.0, "west" => -70.0, "east" => -50.0}
+      assert [%{lat: 53.0, lon: -60.0}] = ScalarFile.read_bounds_hrdps(vt, bounds)
+    end
+
+    test "read_bounds_hrdps returns [] when no HRDPS dir exists" do
+      vt = ~U[2026-04-29 12:00:00Z]
+      ScalarFile.write!(vt, [sample_row(33.0, -97.0, 22.0)])
+
+      assert ScalarFile.read_bounds_hrdps(vt, nil) == []
+    end
+
+    test "list_valid_times_hrdps returns times from HRDPS-suffixed dirs only" do
+      vt1 = ~U[2026-04-29 12:00:00Z]
+      vt2 = ~U[2026-04-29 13:00:00Z]
+      vt_hrrr_only = ~U[2026-04-29 14:00:00Z]
+
+      hand_write_chunk(ScalarFile.dir_for_hrdps(vt1), 53.0, -60.0, 8.0)
+      hand_write_chunk(ScalarFile.dir_for_hrdps(vt2), 53.0, -60.0, 9.0)
+      ScalarFile.write!(vt_hrrr_only, [sample_row(33.0, -97.0, 22.0)])
+
+      assert ScalarFile.list_valid_times_hrdps() == [vt1, vt2]
+    end
+  end
+
   defp hand_write_chunk(dir, lat, lon, temp) do
     File.mkdir_p!(dir)
     lat_band = (lat / 5) |> Float.floor() |> trunc()

test/microwaveprop_web/controllers/weather_tile_controller_test.exs

@@ -3,6 +3,7 @@ defmodule MicrowavepropWeb.WeatherTileControllerTest do
 
   alias Microwaveprop.Propagation.ProfilesFile
   alias Microwaveprop.Weather.GridCache
+  alias Microwaveprop.Weather.ScalarFile
 
   setup do
     GridCache.clear()
@@ -110,5 +111,59 @@ defmodule MicrowavepropWeb.WeatherTileControllerTest do
       body = response(conn, 200)
       assert <<"WCEL", 1::8, 0::little-32, _layer_count::8, _rest::binary>> = body
     end
+
+    test "with ?source=hrdps returns only HRDPS rows (skips HRRR scalars and ProfilesFile)", %{conn: conn} do
+      valid_time = ~U[2026-04-28 12:00:00Z]
+
+      # HRRR side: write a Texas row via the standard pipeline.
+      ProfilesFile.write!(valid_time, %{
+        {33.0, -97.0} => %{
+          surface_temp_c: 22.0,
+          surface_dewpoint_c: 12.0,
+          surface_pressure_mb: 1010.0,
+          hpbl_m: 800.0,
+          pwat_mm: 25.0,
+          profile: []
+        }
+      })
+
+      # HRDPS side: hand-write a Canadian chunk into the HRDPS sibling dir.
+      hrdps_dir = ScalarFile.dir_for_hrdps(valid_time)
+      File.mkdir_p!(hrdps_dir)
+      lat_band = (53.0 / 5) |> Float.floor() |> trunc()
+      lon_band = (-60.0 / 5) |> Float.floor() |> trunc()
+      path = Path.join(hrdps_dir, "#{lat_band}_#{lon_band}.mp.gz")
+
+      payload =
+        Msgpax.pack!(
+          [
+            %{
+              "lat" => 53.0,
+              "lon" => -60.0,
+              "valid_time" => "2026-04-28T12:00:00Z",
+              "temperature" => 8.0,
+              "surface_rh" => 70.0
+            }
+          ],
+          iodata: false
+        )
+
+      File.write!(path, :zlib.gzip(payload))
+
+      time = DateTime.to_iso8601(valid_time)
+
+      conn =
+        get(
+          conn,
+          ~p"/weather/cells?time=#{time}&south=40.0&north=70.0&west=-150.0&east=-50.0&source=hrdps"
+        )
+
+      body = response(conn, 200)
+      assert <<"WCEL", 1::8, cell_count::little-32, _rest::binary>> = body
+      # Only the Canadian (53, -60) row — HRRR's (33, -97) is excluded.
+      assert cell_count == 1
+
+      File.rm_rf!(hrdps_dir)
+    end
   end
 end

test/microwaveprop_web/live/weather_ca_map_live_test.exs

@@ -0,0 +1,57 @@
+defmodule MicrowavepropWeb.WeatherCaMapLiveTest do
+  # async: false because we touch the shared scalar / profile dirs.
+  use MicrowavepropWeb.ConnCase, async: false
+
+  import Phoenix.LiveViewTest
+
+  alias Microwaveprop.Propagation.ProfilesFile
+  alias Microwaveprop.Weather.GridCache
+
+  setup do
+    GridCache.clear()
+
+    on_exit(fn ->
+      GridCache.clear()
+      ProfilesFile.prune_older_than(~U[2099-12-31 23:59:59Z])
+    end)
+
+    :ok
+  end
+
+  test "mounts at /weather-ca with Canadian default viewport", %{conn: conn} do
+    {:ok, _lv, html} = live(conn, ~p"/weather-ca")
+
+    # Default viewport is centered roughly on central Canada at a low
+    # zoom — different from /weather's DFW@z7. The exact numbers are
+    # asserted so a routing accident (mounting WeatherMapLive at this
+    # path by mistake) is caught.
+    assert html =~ ~s(data-initial-lat="55.0")
+    assert html =~ ~s(data-initial-lon="-100.0")
+    assert html =~ ~s(data-initial-zoom="4")
+  end
+
+  test "renders the weather map element with data-source=hrdps", %{conn: conn} do
+    {:ok, _lv, html} = live(conn, ~p"/weather-ca")
+
+    # The JS hook reads data-source and appends &source=hrdps to its cell
+    # fetches. Without this attribute the page would silently fall back
+    # to HRRR-only reads and never show Canadian data.
+    assert html =~ ~s(data-source="hrdps")
+  end
+
+  test "viewport_changed event push_patches /weather-ca, not /weather", %{conn: conn} do
+    {:ok, lv, _html} = live(conn, ~p"/weather-ca")
+
+    render_hook(lv, "viewport_changed", %{"lat" => 60.0, "lon" => -110.0, "zoom" => 5})
+
+    assert_patch(lv, "/weather-ca?layer=temperature&lat=60.0&lon=-110.0&zoom=5")
+  end
+
+  test "select_layer push_patches a /weather-ca URL", %{conn: conn} do
+    {:ok, lv, _html} = live(conn, ~p"/weather-ca")
+
+    render_hook(lv, "select_layer", %{"layer" => "pwat"})
+
+    assert_patch(lv, "/weather-ca?layer=pwat&lat=55.0&lon=-100.0&zoom=4")
+  end
+end