notificationReceived (payload) {
		this.notificationWeatherObject = payload;

		// setCurrentWeather combines the newly received notification weather with
		// the existing weather object we return for current weather
		this.setCurrentWeather(this.currentOverrideWeatherObject);
		this.updateAvailable();
	}
Updates the overrideWeatherObject, calls setCurrentWeather to combine it with
the existing current weather object provided by the base provider, and signals
that an update is ready.
@param {WeatherObject} payload - the weather object received from the CURRENT_WEATHER_OVERRIDE
                                 notification. Represents information to augment the
                                 existing currentOverrideWeatherObject with.