diff --git a/lib/microwaveprop/weather.ex b/lib/microwaveprop/weather.ex
index b89b23f2..540994bd 100644
--- a/lib/microwaveprop/weather.ex
+++ b/lib/microwaveprop/weather.ex
@@ -257,11 +257,12 @@ defmodule Microwaveprop.Weather do
   end
 
   @doc """
-  Delete HRRR grid profiles older than 48 hours that sit on the 0.125° grid.
+  Delete HRRR grid profiles older than 24 hours that sit on the 0.125° grid.
   Preserves QSO-linked profiles which are at arbitrary lat/lon positions.
+  With 19 forecast hours per run, this keeps ~2 runs worth of grid profiles.
   """
   def prune_old_grid_profiles do
-    cutoff = DateTime.add(DateTime.utc_now(), -48, :hour)
+    cutoff = DateTime.add(DateTime.utc_now(), -24, :hour)
     step = 0.125
 
     {deleted, _} =