diff --git a/docs/CHANGELOG.md b/docs/CHANGELOG.md
index 17275e70..6d3f972a 100755
--- a/docs/CHANGELOG.md
+++ b/docs/CHANGELOG.md
@@ -1,6 +1,21 @@
 All notable changes to this project will be documented in this file.
 We follow the [Semantic Versioning 2.0.0](http://semver.org/) format.
 
+## v4.5.13.6 - 2025-1-10 - [PR#1387](https://github.com/NOAA-OWP/inundation-mapping/pull/1387)
+
+Fixes two issues in test_cases:
+1. An error in `synthesize_test_cases` and `run_test_case` if any directories of the 5 benchmark sources (BLE, NWS, IFC, USGS, or ras2fim) do not exist. This issue was originally discovered and fixed in #1178, but is being elevated to its own PR here. Fixes #1386.
+2. Updated `run_test_cases` to accommodate levee and waterbody masking in Alaska. As part of these changes, hardcoded paths were replaced by environment variables.
+
+### Changes
+
+- `tools/`
+    - `run_test_case.py`: Fixed error if missing validation data. Updated masking data to include Alaska.
+    - `synthesize_test_cases.py`: Fixed error if missing validation data.
+    
+<br/><br/>
+
+
 ## v4.5.13.5 - 2025-01-09 - [PR#1389](https://github.com/NOAA-OWP/inundation-mapping/pull/1389)
 
 Updates Python packages to resolve dependency conflicts that were preventing `Dockerfile.dev` to build on Mac. This also resolves two security warnings: https://github.com/NOAA-OWP/inundation-mapping/security/dependabot/51 and https://github.com/NOAA-OWP/inundation-mapping/security/dependabot/52.
@@ -12,7 +27,6 @@ Updates Python packages to resolve dependency conflicts that were preventing `Do
 <br/><br/>
 
 
-
 ## v4.5.13.4 - 2024-01-03 - [PR#1382](https://github.com/NOAA-OWP/inundation-mapping/pull/1382)
 
 Cleans up Python files within `delineate_hydros_and_produce_HAND.sh` to improve performance, especially memory management, including removing unused imports, deleting object references when objects are no longer needed, and removing GDAL from the `fim_process_unit_wb.sh` step of FIM pipeline. Contributes to #1351 and #1376.
diff --git a/tools/run_test_case.py b/tools/run_test_case.py
index efb2f22e..4180b89d 100755
--- a/tools/run_test_case.py
+++ b/tools/run_test_case.py
@@ -54,6 +54,9 @@ def magnitudes(self):
     def huc_data(self):
         '''Returns a dict of HUC8, magnitudes, and sites.'''
         huc_mags = {}
+        if not os.path.exists(self.validation_data):
+            return huc_mags
+
         for huc in os.listdir(self.validation_data):
             if not re.match(r'\d{8}', huc):
                 continue
@@ -126,19 +129,30 @@ def __init__(self, test_id, version, archive=True):
         # Benchmark data path
         self.benchmark_dir = os.path.join(self.validation_data, self.huc)
 
-        # Create list of shapefile paths to use as exclusion areas.
-        self.mask_dict = {
-            'levees': {
-                'path': '/data/inputs/nld_vectors/Levee_protected_areas.gpkg',
-                'buffer': None,
-                'operation': 'exclude',
-            },
-            'waterbodies': {
-                'path': '/data/inputs/nwm_hydrofabric/nwm_lakes.gpkg',
-                'buffer': None,
-                'operation': 'exclude',
-            },
-        }
+        if self.huc[:2] == '19':
+            self.mask_dict = {
+                'levees': {
+                    'path': os.getenv('input_nld_levee_protected_areas_Alaska'),
+                    'buffer': None,
+                    'operation': 'exclude',
+                },
+                'waterbodies': {
+                    # 'path': '/data/inputs/nwm_hydrofabric/nwm_lakes.gpkg',
+                    'path': os.getenv('input_nwm_lakes_Alaska'),
+                    'buffer': None,
+                    'operation': 'exclude',
+                },
+            }
+
+        else:
+            self.mask_dict = {
+                'levees': {
+                    'path': os.getenv('input_nld_levee_protected_areas'),
+                    'buffer': None,
+                    'operation': 'exclude',
+                },
+                'waterbodies': {'path': os.getenv('input_nwm_lakes'), 'buffer': None, 'operation': 'exclude'},
+            }
 
     @classmethod
     def list_all_test_cases(cls, version, archive, benchmark_categories=[]):
diff --git a/tools/synthesize_test_cases.py b/tools/synthesize_test_cases.py
index ab734bf7..9118f56f 100755
--- a/tools/synthesize_test_cases.py
+++ b/tools/synthesize_test_cases.py
@@ -115,6 +115,9 @@ def create_master_metrics_csv(
     # Iterate through 5 benchmark sources
     for benchmark_source in ['ble', 'nws', 'usgs', 'ifc', 'ras2fim']:
         benchmark_test_case_dir = os.path.join(TEST_CASES_DIR, benchmark_source + '_test_cases')
+        if not os.path.exists(benchmark_test_case_dir):
+            continue
+
         test_cases_list = [d for d in os.listdir(benchmark_test_case_dir) if re.match(r'\d{8}_\w{3,7}', d)]
 
         if benchmark_source in ['ble', 'ifc', 'ras2fim']: