Snow occurs when water vapor in an air mass is cooled below freezing. Density of snow varies greatly. Some storms produce "wet" snow like wet sand, others "dry" snow like sawdust. Wet or heavy snow can often be plowed away. Time is of the essence. Use of reliable weather forecasting services allows for crew readiness in advance of storms. Salt, either as a pre-wetted granular product or as brine, should be applied before or at the outset of a snowstorm as an anti-icing treatment to prevent bonding of the frozen precipitation to the pavement or, as a deicer, as soon as snow or ice begins to accumulate.

Winter storms produce a number of hazardous conditions other than snow. Even without rain, ice may occur when moist air contacts a cold surface, particularly on bridge decks. Rain may freeze as it falls on pavement. Frozen rain falls as sleet or hail; it may stick to pavements. Anti-icing can be particularly beneficial in frost prevention.

There are roughly five major kinds of storms. Each requires a somewhat different approach. Everyone on the maintenance force should know these basic kinds of storms and how to combat them.

Stormfighting Guidelines

The following chart is a guideline to combat various types of storms.   Local conditions and policies will be the final determining factor.

*  Note:  The light, 200 lbs. per two-lane mile application called for in Conditions 1 and 2 must be repeated often for the duration of the condition.

Most storms occur under Conditions 1, 2, or 3. But variations in temperature, precipitation, pavement condition or other factors are common. Management must depend upon well-trained maintenance crews to use initiative and imagination in coping with unforeseen problems.

Pavement will often "freeze dry" following a storm, if the last salt application is properly timed. Often, moisture on the pavement will turn to vapor and evaporate as it freezes, leaving a completely clear, dry surface.

Keep an eye on the weather. Proper preparation for a storm improves when management anticipates when it will arrive, how long it will last and the nature of its special characteristics. Use the U.S. Weather Bureau, local media forecasts or a private forecasting service to get complete, detailed reports during winter. Some maintenance departments hire a private forecaster to assure a balanced and more localized weather picture, as well as special advance notice. Some larger agencies are using pavement sensors and local weather instruments to receive actual pavement and atmospheric conditions for more precise forecasts and operations. The Internet has free online services such as The Weather Channel, Accuweather,
and the National Weather Service.

Changes in weather conditions should be relayed to all personnel. If late afternoon reports indicate possibility of overnight snowfall, prepare equipment by attaching snowplows and spreaders before the workday ends. If weather forecasts indicate, a certain portion of the work force should remain on duty to start fighting the storm when it arrives. If the forecast indicates snow during the night, the work force should be sent home to get some rest, but alerted that they may be called back during the night. Arrange with the highway patrol, local police, sheriff's department or weather service to notify key personnel of storms that develop late at night. Ensure that someone is responsible for relaying the alert to the entire maintenance force, if and when the need arises. Some agencies anti-ice with a protective brine spray to roadways before going home the night before a forecast storm to prevent bonding of the snow and ice to the pavement.

Pounds of Ice Melted Per Pound of Salt

Application of Salt

          Note:  Salt meeting ASTM Specification D-632 weighs approximately 80 pounds per cubic foot.  While ASTM is the standard spec., both AASHTO and Pacific Northwest Snowfighters have independent specifications.

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