NOAA's National Weather Service - Birmingham, Alabama

· Winter Storm Outlook (SPS)
A "Winter Storm Outlook" may be issued when there is a 30% or greater chanceof a major winter storm, but the occurrence is expected to be within 3-7 days. It is intended to provide information to those who need considerable lead time to prepare for the event. This product is issued as a "Special Weather Statement".
· Winter Storm Watch (WSW)
A "Winter Storm Watch" will be issued when conditions are favorable for hazardous winter weather conditions to develop. Unlike a Tornado Watch or a Severe Thunderstorm Watch, Winter Storm Watches are issued by the local office. Generally, this type of watch is issued for weather conditions that could occur 12 to 48 hours in the future. Information in the watch will include the affected area, the weather threat involved, potential precipitation amounts, explanation of what a watch is, the uncertainty involved, precautions recommended, and the storm's potential impact. NWS Birmingham issues a Winter Storm Watch when one or more of the following is possible (50% or greater confidence) during the next 12 to 48 hours: · Snowfall of 2+ inches in 12 hours · Accumulation of freezing rain (ice) greater than 0.05". · Accumulation of sleet (ice pellets) greater than 0.50".
· Winter Storm Warning (WSW)
A "Winter Storm Warning" is issued when a combination of hazardous winter weather is occurring, is imminent, or is expected. Winter Storm Warnings are issued when one or more of the following is expected: · Snowfall of 2+ inches in 12 hours · Accumulation of freezing rain (ice) greater than 0.05". · Accumulation of sleet (ice pellets) greater than 0.50".
· Blizzard Warning (WSW)
A "Blizzard Warning" will be issued when winds of 35 mph (sustained or frequent gusts) or stronger combine with considerable falling, blowing, and/or drifting snow, for 3 hours or more with visibilities of 1/4 mile or less. This condition will be extremely infrequent in central Alabama.
· Heavy Snow Warning (WSW)
A "Heavy Snow Warning" is issued when snowfall of 2+ inches in 12 hours. If strong winds and low wind chills are expected in addition to the heavy snow, then a Winter Storm Warning or Blizzard Warning will be issued instead.
· Ice Storm Warning (WSW)
An "Ice Storm Warning" is issued when greater than 0.25" of ice is expected during freezing rain situations. Heavy accumulations of ice produce extremely dangerous and damaging situations, primarily by pulling down trees and utility lines.
· Winter Weather Advisory (WSW)
A "Winter Weather Advisory" is issued for a winter weather situation that causes significant inconveniences, but does not meet warning (see above) criteria. The winter weather can still be life threatening if caution is not exercised. A Winter Weather Advisory is issued if more than one type of hazardous winter weather is expected, is occurring, or is imminent: · Snowfall of 0.25 to 2.0 inches in 12 hours · Accumulation of freezing rain (ice) less than 0.05". · Accumulation of sleet (ice pellets) less than 0.50".
· Blowing Snow Advisory (WSW)
A "Blowing Snow Advisory" is issued if blowing snow is expected to reduce visibilities to around 1/2 mile or less, causing hazardous travel. This can also be issued for drifting snow, in which case it is called a "Drifting Snow Advisory." The two can also be combined. This is also very infrequent in central Alabama.
· Snow Advisory (WSW)
A "Snow Advisory" is issued when snow is expected to accumulate 0.254 to 2.0 inches in a 12-hour period.
· Freezing Drizzle Advisory (WSW)
A "Freezing Drizzle Advisory" is issued to give advance notice that drizzle will create a light coating of ice (a glaze) on exposed surfaces and objects. Walking and driving can become treacherous in these conditions.
· Freezing Rain Advisory (WSW)
A "Freezing Rain Advisory" is issued when rain freezes, or is expected to freeze, on surfaces and objects, making walking and travel dangerous. Accumulations would be less than 0.05". Heavy accumulations of ice would require an Ice Storm Warning (see above).