diff --git a/lib/microwaveprop/weather/narr_client.ex b/lib/microwaveprop/weather/narr_client.ex
index b787794b..a170c8e9 100644
--- a/lib/microwaveprop/weather/narr_client.ex
+++ b/lib/microwaveprop/weather/narr_client.ex
@@ -294,7 +294,7 @@ defmodule Microwaveprop.Weather.NarrClient do
       grb_path
     ]
 
-    case System.cmd("cdo", args, stderr_to_stdout: false) do
+    case System.cmd("cdo", args, stderr_to_stdout: true) do
       {stdout, 0} ->
         parse_cdo_outputtab(stdout)
 
@@ -312,7 +312,11 @@ defmodule Microwaveprop.Weather.NarrClient do
       |> Enum.reduce(%{}, &accumulate_cdo_row/2)
 
     if raw == %{} do
-      {:error, "NARR cdo extract: no parseable values in cdo output"}
+      # Include the first 500 chars of cdo output so the error surfaces
+      # what cdo actually printed — crucial for diagnosing year-specific
+      # parameter-table quirks in NARR GRIB1.
+      snippet = stdout |> String.slice(0, 500) |> String.replace("\n", " | ")
+      {:error, "NARR cdo extract: no parseable values in cdo output (got: #{snippet})"}
     else
       {:ok, build_profile_attrs(raw)}
     end