diff --git a/lib/microwaveprop/weather.ex b/lib/microwaveprop/weather.ex
index 4bd393e7..b89b23f2 100644
--- a/lib/microwaveprop/weather.ex
+++ b/lib/microwaveprop/weather.ex
@@ -256,6 +256,33 @@ defmodule Microwaveprop.Weather do
     {Float.round(lat / 1.0, 2), Float.round(lon / 1.0, 2)}
   end
 
+  @doc """
+  Delete HRRR grid profiles older than 48 hours that sit on the 0.125° grid.
+  Preserves QSO-linked profiles which are at arbitrary lat/lon positions.
+  """
+  def prune_old_grid_profiles do
+    cutoff = DateTime.add(DateTime.utc_now(), -48, :hour)
+    step = 0.125
+
+    {deleted, _} =
+      Repo.delete_all(
+        from(h in HrrrProfile,
+          where:
+            h.valid_time < ^cutoff and
+              fragment("? = round(?::numeric / ? ) * ?", h.lat, h.lat, ^step, ^step) and
+              fragment("? = round(?::numeric / ? ) * ?", h.lon, h.lon, ^step, ^step)
+        )
+      )
+
+    if deleted > 0 do
+      require Logger
+
+      Logger.info("Pruned #{deleted} old HRRR grid profiles (keeping QSO profiles)")
+    end
+
+    deleted
+  end
+
   def round_to_iemre_grid(lat, lon) do
     {Float.round(lat * 8) / 8, Float.round(lon * 8) / 8}
   end
diff --git a/lib/microwaveprop/workers/propagation_grid_worker.ex b/lib/microwaveprop/workers/propagation_grid_worker.ex
index 64aa0d5e..963c9942 100644
--- a/lib/microwaveprop/workers/propagation_grid_worker.ex
+++ b/lib/microwaveprop/workers/propagation_grid_worker.ex
@@ -53,6 +53,8 @@ defmodule Microwaveprop.Workers.PropagationGridWorker do
     Logger.info("PropagationGrid: resuming backfill queues")
     Enum.each(@pause_queues, &Oban.resume_queue(queue: &1))
 
+    Weather.prune_old_grid_profiles()
+
     result
   end