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Forecasters at the NWS Norman forecast office provide a variety of services to help keep you informed about winter weather. Outlooks, watches, warnings and advisories provide specific localized information for your county detailing the what, where, why and when of winter weather. Here is a summary of the basic services provided and what the terms mean:
Issued when significant winter precipitation is possible in the next three to five days. An outlook does not guarantee the event will occur, but should be a "heads-up" to monitor later forecasts and information.
Issued when significant winter precipitation is possible in the 24 to 48 hours. Again, a watch does not mean it’s a sure thing, but is designed to alert you to the fact that hazardous winter weather could occur. Watches are issued for winter storms, heavy snow or blizzards.
Issued when winter precipitation that could lead to a threat to life or property is expected. A warning is the most serious of the winter weather messages and indicates that action should be taken immediately to get ready for the storm. Warnings are issued for winter storms, ice storms, heavy snow, blizzards and heavy sleet.
Issued for winter precipitation that is not expected to produce significant risks to life and/or property, but that could still impact travel or other activities. Advisories are issued for a variety of winter weather conditions.
This term may refer to a combination of winter precipitation, including snow, sleet, freezing rain, etc.
In Oklahoma, heavy snow is defined as four or more inches of snow accumulating in a 12-hour period, or six or more inches accumulating in a 24-hour period.
Rain drops that freeze into pellets of ice before reaching the ground. Sleet usually bounces when hitting a surface and does not stick to objects. However, it can accumulate and cause dangerous driving conditions.
Rain that falls onto a surface where the temperature is below freezing. This causes the rain to freeze on contact with trees, power lines, cars and roads. This coating or glaze of ice causes serious travel problems, even with very small accumulations.
A high impact event caused by excessive accumulations of freezing rain on trees and power lines. Generally, a quarter of an inch or more of ice is considered dangerous. However, this can vary depending on other factors.
This life-threatening event is produced by a combination of falling or blowing snow, and high winds, typically 35 mph or more for a prolonged period of time. This combination can create potentially deadly travel conditions with impassable roads and zero visibilities.
The combination of wind and temperature that serves as an estimate of how cold it actually feels to exposed human skin. Wind chill values below -19 degrees are considered dangerous