diff --git a/lib/nexrad/archive.py b/lib/nexrad/archive.py
index dcf5dd8..ebd1e32 100644
--- a/lib/nexrad/archive.py
+++ b/lib/nexrad/archive.py
@@ -1,4 +1,5 @@
 import os
+import re
 
 from nexrad.s3 import S3Bucket
 
@@ -21,3 +22,49 @@ class Archive():
 
         with open(path, 'wb') as fh:
             self.bucket.s3.download_fileobj(self.bucket.name, key, fh)
+
+    RE_YEAR      = re.compile(r'^\d{4}$')
+    RE_MONTH_DAY = re.compile(r'^\d{2}$')
+    RE_CALL      = re.compile(r'^[A-Z]{4}$')
+    RE_PRODUCT   = re.compile(r'^([A-Z]{4})(\d{4})(\d{2})(\d{2})_(\d{2})(\d{2})(\d{2})')
+
+    def each_downloaded_key(self):
+        parts = [self.path]
+
+        for year in os.scandir(os.path.join(*parts)):
+            if not (year.is_dir() and self.RE_YEAR.match(year.name)):
+                continue
+
+            parts.append(year.name)
+
+            for month in os.scandir(os.path.join(*parts)):
+                if not (month.is_dir() and self.RE_MONTH_DAY.match(month.name)):
+                    continue
+
+                parts.append(month.name)
+
+                for day in os.scandir(os.path.join(*parts)):
+                    if not (day.is_dir() and self.RE_MONTH_DAY.match(day.name)):
+                        continue
+
+                    parts.append(day.name)
+
+                    for call in os.scandir(os.path.join(*parts)):
+                        if not (call.is_dir() and self.RE_CALL.match(call.name)):
+                            continue
+
+                        parts.append(call.name)
+
+                        for item in os.scandir(os.path.join(*parts)):
+                            if not (item.is_file() and self.RE_PRODUCT.match(item.name)):
+                                continue
+
+                            yield '/'.join([*parts[1:], item.name])
+
+                        parts.pop()
+
+                    parts.pop()
+
+                parts.pop()
+
+            parts.pop()