What Does ‘Significant’ Mean with Ice and Snow Accumulations?

As the winter storm season approaches, understanding what constitutes "significant" ice and snow accumulations can help you better prepare for hazardous conditions. The National Weather Service (NWS) has issued a Winter Storm Watch for much of Southern Indiana, parts of southern Illinois, western Kentucky, southeast Missouri, and beyond. This system is expected to bring a wintry mix, including freezing rain, sleet, snow, and rain, with potentially dangerous accumulations of ice and snow.

Winter Storm Watch: What to Expect

The Winter Storm Watch will be in effect from late Saturday night through late Sunday night. Here are the key details:

• What:
  • Heavy mixed precipitation is possible.
  • Total snow and sleet accumulations of 4 inches or more.
  • Ice accumulations of one-quarter inch or more.
• Where:
  • Portions of Southern Indiana, southern Illinois, and western Kentucky.
• When:
  • From late Saturday night through late Sunday night.
• Impacts:
  • Power outages and tree damage are possible due to the weight of ice.
  • Travel could be nearly impossible on untreated roads.
  • The hazardous conditions could impact the Monday morning commute.

Read More: Why Hoosiers Should Put a Quarter in Their Freezer Right Now

Understanding "Significant" Ice Accumulations

The National Weather Service uses the term "significant" to describe amounts of snow and ice that could disrupt daily life and create dangerous situations. Based on the latest NWS graphics:

• Freezing Rain Risk:
  • There’s a high probability of freezing rain leading to at least one-tenth of an inch of ice.
  • Accumulations of one-quarter inch or more are also possible, especially in the Watch Area.
• Snow and Sleet:
  • While freezing rain poses the greatest concern, snow and sleet accumulations of 4 inches or more could exacerbate road conditions and increase the risk of power outages.

Meteorologist Ron Rhodes with ABC 25 WEHT

Explaining the Graphics

The attached National Weather Service graphics break down the probabilities of freezing rain and ice accumulation:

1. Probability of 0.10” Ice Accumulation:
   • This graphic shows the likelihood of areas receiving at least one-tenth of an inch of ice. This level of accumulation is enough to cause slick roads and power line stress.
2. Probability of 0.25” Ice Accumulation:
   • This highlights areas where at least one-quarter inch of ice is likely. Such accumulations can lead to significant power outages, downed trees, and treacherous travel conditions.

These graphics indicate a strong signal of freezing rain across much of the region, with some uncertainty still present in the models. However, they underscore the importance of preparation for the Watch Area.

Related: Southern Indiana Winter Storm Alert: Get Ready With Essentials

What This Means for You

The upcoming winter storm could bring significant accumulations of ice and snow, making travel and daily life difficult or even dangerous. Residents in Southern Indiana and surrounding areas should:

• Stay informed by monitoring weather updates.
• Prepare for potential power outages by having supplies ready.
• Avoid travel unless absolutely necessary.

Stay Ahead of the Storm

This winter storm is shaping up to be a serious event, with impacts expected late Saturday through Sunday night. Freezing rain, sleet, snow, and dangerous ice accumulations are all on the table. The hazardous conditions could linger into the workweek, so make sure you’re ready.

Get our free mobile app

Continue to check the latest forecasts and updates from the National Weather Service to stay safe during this winter weather event.