diff --git a/modules/amv/intercompare.py b/modules/amv/intercompare.py
index 412c682f23e0e0ccd04ebc59859bfecc84da75b1..afe68d6ac35c59e3669984069677d3813fb302ff 100644
--- a/modules/amv/intercompare.py
+++ b/modules/amv/intercompare.py
@@ -1125,13 +1125,15 @@ def best_fit_altitude(amv_spd, amv_dir, amv_alt, amv_lat, amv_lon, fcst_spd, fcs
         if a2 < sat_wind_best_fit_alt:
             lev_below = imin
             lev_above = imin + 1
-            Prop = (sat_wind_best_fit_alt - a2) / (a3 - a2)
+            prop = (sat_wind_best_fit_alt - a2) / (a3 - a2)
         else:
+            lev_below = imin - 1
+            lev_above = imin
+            prop = (sat_wind_best_fit_alt - a1) / (a2 - a1)
             pass
 
-        sat_wind_best_fit_u = fcst_uwind[lev_below] * (1.0 - Prop) + fcst_uwind[lev_above] * Prop
-        sat_wind_best_fit_v = fcst_vwind[lev_below] * (1.0 - Prop) + fcst_vwind[lev_above] * Prop
-
+        sat_wind_best_fit_u = fcst_uwind[lev_below] * (1.0 - prop) + fcst_uwind[lev_above] * prop
+        sat_wind_best_fit_v = fcst_vwind[lev_below] * (1.0 - prop) + fcst_vwind[lev_above] * prop
 
 
     return bf_tup