Whenever the Mayor, or in his absence, the President of Council, finds, on the basis of falling snow, sleet, or freezing rail, or on the basis of a forecast, by the United States Weather Bureau or other weather service of snow, sleet, or freezing rain, that weather conditions will make it necessary that motor vehicle traffic be expedited and that parking on certain Village streets be prohibited or restricted for snow plowing and other purposes, he shall put into effect a parking prohibition on parts of or all snow emergency routes as necessary.