diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index 045a10e5..d3595297 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -172,14 +172,15 @@ jobs:
           if [[ "$MF6_REMOTE" != "$req_remote" ]]; then echo "bad mf6 remote in .mf6_ci_ref_remote"; exit 1; fi
 
       - name: Setup gfortran
+        if: runner.os != 'macOS'
         uses: fortran-lang/setup-fortran@v1
         with:
           compiler: gcc
           version: 11
 
-      - name: Link gfortran dylibs on Mac
-        if: runner.os == 'macOS'
-        run: .github/scripts/symlink_gfortran_mac.sh
+      # - name: Link gfortran dylibs on Mac
+      #   if: runner.os == 'macOS'
+      #   run: .github/scripts/symlink_gfortran_mac.sh
 
       - name: Install Dependencies via Micromamba
         uses: mamba-org/setup-micromamba@v1.9.0
diff --git a/autotest/ci_local.sh b/autotest/ci_local.sh
index 557ae5e0..aac220e9 100755
--- a/autotest/ci_local.sh
+++ b/autotest/ci_local.sh
@@ -464,30 +464,30 @@ if [ -z "${t}" ]; then
             --domain=ucb_2yr \
             --control_pattern=nhm.control \
             --durations=0 || exit 1
-    fi
 
-    if [ -z "${g}" ]; then
-        echo
+        if [ -z "${g}" ]; then
+            echo
+            echo ".........."
+            echo "ucb_2yr_nhm_transp_frost - generate and manage test data"
+            echo ".........."
+            echo
+            python generate_test_data.py \
+                -n=$pytest_n --domain=ucb_2yr --control_pattern=frost.control \
+                --remove_prms_csvs --remove_prms_output_dirs || exit 1
+        fi
+
         echo ".........."
-        echo "ucb_2yr_nhm_transp_frost - generate and manage test data"
+        echo "ucb_2yr_nhm_transp_frost - pywatershed tests"
         echo ".........."
         echo
-        python generate_test_data.py \
-            -n=$pytest_n --domain=ucb_2yr --control_pattern=frost.control \
-            --remove_prms_csvs --remove_prms_output_dirs || exit 1
+        pytest \
+            -vv \
+            -n=$pytest_n \
+            test_prms_atmosphere_transp_frost.py \
+            --domain=ucb_2yr \
+            --control_pattern=frost.control \
+            --durations=0 || exit 1
     fi
-
-    echo ".........."
-    echo "ucb_2yr_nhm_transp_frost - pywatershed tests"
-    echo ".........."
-    echo
-    pytest \
-        -vv \
-        -n=$pytest_n \
-        test_prms_atmosphere_transp_frost.py \
-        --domain=ucb_2yr \
-        --control_pattern=frost.control \
-        --durations=0 || exit 1
 fi
 
 if [ -z "${i}" ]; then
diff --git a/bin/prms_mac_m1_gfortran_clang_dbl_prec b/bin/prms_mac_m1_gfortran_clang_dbl_prec
new file mode 100755
index 00000000..9b6ff72a
Binary files /dev/null and b/bin/prms_mac_m1_gfortran_clang_dbl_prec differ
diff --git a/bin/prms_mac_m1_gfortran_clang_single_prec b/bin/prms_mac_m1_gfortran_clang_single_prec
new file mode 100755
index 00000000..ba2dea77
Binary files /dev/null and b/bin/prms_mac_m1_gfortran_clang_single_prec differ
diff --git a/environment.yml b/environment.yml
index 4eebe6eb..a3192d48 100644
--- a/environment.yml
+++ b/environment.yml
@@ -14,6 +14,7 @@ dependencies:
   - folium
   - geopandas
   - geoviews
+  - gfortran
   - git
   - holoviews<=1.20.0
   - hvplot
diff --git a/environment_w_jupyter.yml b/environment_w_jupyter.yml
index 262cf17f..983e0e1f 100644
--- a/environment_w_jupyter.yml
+++ b/environment_w_jupyter.yml
@@ -14,6 +14,7 @@ dependencies:
   - folium
   - geopandas
   - geoviews
+  - gfortran
   - git
   - holoviews<=1.20.0
   - hvplot
diff --git a/prms_src/prms5.2.1/makelist_double_precision b/prms_src/prms5.2.1/makelist_double_precision
index 223f23cc..260ea1a8 100644
--- a/prms_src/prms5.2.1/makelist_double_precision
+++ b/prms_src/prms5.2.1/makelist_double_precision
@@ -102,7 +102,7 @@ ifeq ($(detected_OS), Windows)
 		CFLAGS = -Dfloat=double $(OPTLEVEL) -D$(ARC) -D_UF -Wall
 	endif
 else
-	ifeq ($(CC), gcc)
+	ifeq ($(CC), $(filter $(CC), gcc clang))
 		CFLAGS = -Dfloat=double $(OPTLEVEL) -D$(ARC) -D_UF -Wall
 	endif
 	ifeq ($(CC), $(filter $(CC), icc mpiicc))
diff --git a/prms_src/prms5.2.1/mmf/defs.h b/prms_src/prms5.2.1/mmf/defs.h
index f3da4772..024a40c8 100644
--- a/prms_src/prms5.2.1/mmf/defs.h
+++ b/prms_src/prms5.2.1/mmf/defs.h
@@ -16,7 +16,7 @@
 #define FALSE 0
 
 #define ftnint int
-#define ftnlen int
+#define ftnlen long
 
 #define M_LONG 1
 #define M_FLOAT 2
@@ -73,4 +73,3 @@
 //#define MAX_SAVE_MAP 5
 
 #endif /* MMS_DEF_H */
-
diff --git a/prms_src/prms5.2.1/mmf/protos.h b/prms_src/prms5.2.1/mmf/protos.h
index 15072c7e..b6ab5d3d 100644
--- a/prms_src/prms5.2.1/mmf/protos.h
+++ b/prms_src/prms5.2.1/mmf/protos.h
@@ -17,7 +17,7 @@
 
 /***  mmf.c  **************************************************/
 extern long setdims_ (void);
-extern long call_modules_ (char *, int);
+extern long call_modules_ (char *, ftnlen);
 
 /***  alloc_space.c  **************************************************/
 #undef EXTERN
diff --git a/test_data/generate/conftest.py b/test_data/generate/conftest.py
index ce263e97..8a608711 100644
--- a/test_data/generate/conftest.py
+++ b/test_data/generate/conftest.py
@@ -64,7 +64,9 @@ def exe():
         exe_name = "prms_win_gfort_dbl_prec.exe"
     elif platform == "darwin":
         if processor() == "arm":
-            exe_name = "prms_mac_m1_ifort_dbl_prec"
+            # exe_name = "prms_mac_m1_ifort_dbl_prec"
+            # Revert this to ifort in final PR
+            exe_name = "prms_mac_m1_gfortran_clang_dbl_prec"
         else:
             exe_name = "prms_mac_intel_gfort_dbl_prec"
     elif platform == "linux":