How Weather Conditions Impact Service

Types of Weather that Could Impact Your Snow Plowing Contract

Black Ice – (glare ice) A thin, unexpected and invisible coating of ice on a roadway or walkway surface. The thin ice appears as the color of the material beneath it. Minute precipitation amounts are adequate to create slippery, unnoticed and dangerous situations, where travelers have minimal indication of weather changes. Fog, alone, in the absence of any falling precipitation can create a slippery coating to smooth, horizontal surfaces. Because it is always so difficult to see, it represents a universal hazard to automotive traffic, cyclists, motorcyclists and pedestrians.

Freezing Fog – When liquid fog droplets freeze to surfaces, forming a white soft or hard rime. This is very common on mountain tops which are exposed to low clouds. It is equivalent to freezing rain, and essentially the same as the ice that forms inside a freezer.

Freezing Rain – Rain that falls when surface temperatures are below freezing causing icing on contact. A storm producing a significative thickness of freezing rain is often referred as an “ice storm”. Freezing rain is notorious for causing travel problems on roadways, breaking tree limbs, and downing power lines.

Sleet – Rain which freezes before reaching the ground that can accumulate creating hazardous driving conditions.

Dry Snow – Snow with little to no liquid water content, thus it is less dense than average. Less dense meaning there will be a lot of air in the snow making it vulnerable to blow in windy conditions. As it warms, it can become very slippery particularily on pedestrian sidewalks.

Wet Snow – Deposited snow that contains a great deal of liquid water and typically occurs at temperatures near freezing. Minor accumulation of wet snow can be very slippery on all hard surfaces.

Heavy Snow – When snowfall accumulation rate is at either four inches (10 cm) or more within 12 hours or six inches (15 cm) or more within 24 hours. Pedestrians, cyclists and drivers should avoid roadways or use extreme caution.

Drifting Snow – The meteorological term for any loose snow lifted from the ground surface and suspended by strong winds to a height of 6 ft or less above the surface. Drifting snow tends to creep, roll and bounce above the surface and is a major hazard for surface transportation.

Blowing snow – The meteorological term for any loose snow lifted from the ground surface and suspended by strong winds to a height of 6 ft or more above the surface. Blowing snow can be falling snow or snow that already accumulated and is one of the classic requirements for a blizzard.

Blizzard – Winds need to reach sustained speeds or frequent gusts of 35 m.p.h. or greater, and visibilities have to be repeatedly reduced to 1/4 mile or less by falling and/or blowing snow for a period of at least three hours. A blizzard can actually occur with clear skies if the visibility reduction is caused by blowing snow. While there are no temperature requirements for a blizzard, the combination of strong winds and below-freezing temperatures will drop windchills at least into the single digits. By definition, the difference between blizzard and a snowstorm is the strength of the wind. Blizzards have a negative impact on local economies and can paralyze regions for days at a time.

It is important to know the existing and potential weather conditions.

  1. Start of Precipitation
  2. Type of Precipitation
  3. Total Precipitation
  4. Expected Event Length
  5. Wind (speed,gust, directions)
  6. Temperature Trend

Most weather stations measure temperature and other conditions 20-30 feet above ground. This means the actual temperature and other conditions can differ substantially from pavement or surface temperatures. A blanket approach will not work, and different strategies are needed. Potomac has the years of experience and expertise to not only properly determine the best method, but our staff also can adjust our method based on changing conditions as they occur. Our goal is to provide immediate response, be proactive in our approach and help reduce environmental impacts from snow and ice conditions.

Contact Potomac for contract information.