When winter weather threatens, your National Weather Service in Jackson issues watch, warning, and advisory products to warn you of the impending hazard.  Winter weather is often the most difficult weather for the ArkLaMiss, both because it causes travel problems, and because it is difficult to forecast.


Winter Weather Definitions  
NWS Jackson will issue winter weather products based on the following definitions:
  • Blizzard: defined as having sustained winds of 35 mph, or frequent gusts to 35 mph or higher as well as considerable falling and/or blowing snow that frequently reduces the visibility to less than 1/4 mile. These conditions are expected to prevail or last for 3 hours or longer.
  • Heavy snow: snowfall accumulations of 2 inches or more in 12 hours or less.
  • Ice/Sleet storm: When freezing rain is expected to accumulate 1/4 inch or greater during a 12-24 hour period. For sleet, the accumulation of 0.5 inches is used.
  • Freezing Rain(or Drizzle): Rain that freezes on objects as it strikes them.
  • Sleet: Solid granules of ice which form from the freezing of super-cooled raindrops or refreezing of largely melted snowflakes.
  • Wind Chill: when wind chill temperatures are expected to fall below 10 degrees. This generally occurs when temperatures are 10 to 15 degrees and wind speeds of 10 to 15 mph.

Winter Storm Outlook (SPS)  
A Winter Storm Outlook may be issued when there is a 30% chance of a major winter storm, but the occurrence is expected to be beyond 48 hours into the future.  It is intended to provide information to those who need considerable lead time to prepare for the event.  This product sometimes is issued as a Special Weather Statement as well.
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 24 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 Jackson issues a Winter Storm Watch when one or more of the following is possible (50% or greater confidence) during the next 12 to 36 hours:

· Snowfall of 2+ inches in 12 hours
· Accumulation of freezing rain (ice) greater than 0.25".
· Greater than 0.50" of sleet accumulation expected.
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 0.25".
·  Greater than 0.50" of sleet accumulation expected.
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 the ArkLaMiss region.
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" freezing rain(ice) or 0.50" of sleet is forecast to accumulate.  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, and frequently a winter weather advisory will be issued if travel impacts can be expected.   A Winter Weather Advisory is issued if more than one type of hazardous winter weather is expected, is occurring, or is imminent:
                                            

· Sleet and/or snowfall of 1-2 inches in 12 hours.
· Accumulation of freezing rain (ice) less than 0.25".

Otherwise, if just one forecast element is expected, an event-specific advisory will be issued, such as those listed below.


Snow Advisory (WSW)  
Snow Advisory is issued when snow is expected to accumulate 1 to 2 inches in a 12-hour period, or if the snowfall will cause travel impacts.
Freezing Rain Advisory (WSW)  
A Freezing Rain Advisory is issued when rain or drizzle freezes, or is expected to freeze, on surfaces and objects, making walking and travel dangerous. Accumulations would be less than 0.25".  Heavy accumulations of ice would require an Ice Storm Warning (see above).
Wind Chill Advisory (WSW)  
A Wind Chill Advisory is issued when cold temperatures and breezy winds combine to create a wind chill 9 degrees and -14 degrees for an hour or more.

Wind Chill Warning (WSW)  
A Wind Chill Warning is issued when cold temperatures and breezy winds combine to create a wind chill below -15 degrees for an hour or more.  
 
 
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