diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index d4b34e33d7..03087eb72f 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -78,6 +78,9 @@ jobs:
             python-version: 3.8
             run-type: script
             test-path: autotest_scripts.py
+        exclude:
+          - os: macos-latest
+            python-version: 3.6
 
     steps:
     # check out repo
@@ -96,9 +99,11 @@ jobs:
     # Standard python fails on windows without GDAL installation
     # Using custom bash shell ("shell: bash -l {0}") with Miniconda
     - name: Setup Miniconda
-      uses: goanpeca/setup-miniconda@v1.6.0
+      uses: conda-incubator/setup-miniconda@v1.7.0
       with:
         python-version: ${{ matrix.python-version }}
+        mamba-version: "*"
+        channels: conda-forge,defaults
         auto-update-conda: true
         auto-activate-base: true
         activate-environment: flopy
@@ -108,12 +113,16 @@ jobs:
       if: matrix.run-type == 'nb'
       shell: bash -l {0}
       run: |
-        conda install -n flopy -c conda-forge jupyter nbconvert
+        mamba install --name flopy jupyter nbconvert
 
-    - name: Add packages to flopy environment
+    - name: Add packages to flopy environment using mamba or conda
       shell: bash -l {0}
       run: |
-        conda env update --name flopy --file etc/environment.yml
+        if [ "$RUNNER_OS" == "Windows" ]; then
+          conda env update --name flopy --file etc/environment.yml
+        else
+          mamba env update --name flopy --file etc/environment.yml
+        fi
 
     - name: Install pymake, xmipy, and flopy
       shell: bash -l {0}
diff --git a/.github/workflows/rtd.yml b/.github/workflows/rtd.yml
index 7d479c57d5..a6080dbe02 100644
--- a/.github/workflows/rtd.yml
+++ b/.github/workflows/rtd.yml
@@ -29,9 +29,11 @@ jobs:
       # Standard python fails on windows without GDAL installation
       # Using custom bash shell ("shell: bash -l {0}") with Miniconda
       - name: Setup Miniconda
-        uses: goanpeca/setup-miniconda@v1.6.0
+        uses: conda-incubator/setup-miniconda@v1.7.0
         with:
           python-version: 3.8
+          mamba-version: "*"
+          channels: conda-forge,defaults
           auto-update-conda: true
           auto-activate-base: true
           activate-environment: flopy
@@ -39,12 +41,12 @@ jobs:
       - name: Add jupyter and jupytext to scripts run
         shell: bash -l {0}
         run: |
-          conda install -n flopy -c conda-forge jupyter jupytext
+          mamba install --name flopy jupyter jupytext
 
       - name: Add packages to flopy environment
         shell: bash -l {0}
         run: |
-          conda env update --name flopy --file etc/environment.yml
+          mamba env update --name flopy --file etc/environment.yml
 
       - name: Install pymake, xmipy, and flopy
         shell: bash -l {0}
@@ -72,11 +74,7 @@ jobs:
 
       - name: Upload completed jupyter notebooks as an artifact for ReadtheDocs
         if:
-          github.repository_owner == 'modflowpy' &&
-          contains(github.ref, '
-          refs/heads/master
-          refs/heads/develop
-          ')
+          github.repository_owner == 'modflowpy' && github.event_name == 'push'
         uses: actions/upload-artifact@v2
         with:
           name: notebooks-for-${{ github.sha }}
@@ -85,11 +83,7 @@ jobs:
 
       - name: Trigger RTDs build on master and develop branches
         if:
-          github.repository_owner == 'modflowpy' &&
-          contains('
-          refs/heads/master
-          refs/heads/develop
-          ', github.ref)
+          github.repository_owner == 'modflowpy' && github.event_name == 'push'
         uses: dfm/rtds-action@v1.0.0
         with:
           webhook_url: ${{ secrets.RTDS_WEBHOOK_URL }}