--- a/python/mozbuild/mozbuild/mach_commands.py
+++ b/python/mozbuild/mozbuild/mach_commands.py
@@ -1,15 +1,16 @@
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, # You can obtain one at http://mozilla.org/MPL/2.0/.
 
 from __future__ import absolute_import, print_function, unicode_literals
 
 import argparse
+import collections
 import errno
 import itertools
 import json
 import logging
 import operator
 import os
 import subprocess
 import sys
@@ -470,31 +471,65 @@ class Build(MachCommandBase):
             # inline output from the compiler itself. However, unlike inline
             # output, this list is sorted and grouped by file, making it
             # easier to triage output.
             #
             # Only do this if we had a successful build. If the build failed,
             # there are more important things in the log to look for than
             # whatever code we warned about.
             if not status:
+                # Suppress warnings for 3rd party projects in local builds
+                # until we suppress them for real.
+                # TODO remove entries/feature once we stop generating warnings
+                # in these directories.
+                LOCAL_SUPPRESS_DIRS = (
+                    'gfx/angle',
+                    'gfx/cairo',
+                    'intl/icu/source',
+                    'js/src/ctypes/libffi',
+                    'media/libtheora',
+                    'media/mtransport/third_party/nICEr',
+                    'media/mtransport/third_party/nrappkit',
+                    'media/webrtc/trunk/webrtc',
+                    'netwerk/sctp/src/netinet',
+                    'nsprpub',
+                    'security/nss',
+                )
+
+                suppressed_by_dir = collections.Counter()
+
                 for warning in sorted(monitor.instance_warnings):
                     path = mozpath.normsep(warning['filename'])
                     if path.startswith(self.topsrcdir):
                         path = path[len(self.topsrcdir) + 1:]
 
                     warning['normpath'] = path
 
+                    if (path.startswith(LOCAL_SUPPRESS_DIRS) and
+                            'MOZ_AUTOMATION' not in os.environ):
+                        for d in LOCAL_SUPPRESS_DIRS:
+                            if path.startswith(d):
+                                suppressed_by_dir[d] += 1
+                                break
+
+                        continue
+
                     if warning['column'] is not None:
                         self.log(logging.WARNING, 'compiler_warning', warning,
                                  'warning: {normpath}:{line}:{column} [{flag}] '
                                  '{message}')
                     else:
                         self.log(logging.WARNING, 'compiler_warning', warning,
                                  'warning: {normpath}:{line} [{flag}] {message}')
 
+                for d, count in sorted(suppressed_by_dir.items()):
+                    self.log(logging.WARNING, 'suppressed_warning',
+                             {'dir': d, 'count': count},
+                             '(suppressed {count} warnings in {dir})')
+
             monitor.finish(record_usage=status==0)
 
         high_finder, finder_percent = monitor.have_high_finder_usage()
         if high_finder:
             print(FINDER_SLOW_MESSAGE % finder_percent)
 
         ccache_end = monitor.ccache_stats()