[KYHAM] KEN Training for Dec. 15: Understanding NWS Winter Weather Information Products

[Ron Dodson]

In last week's training, I commented that the best defense in
winter ttime is to stay informed.  Part of staying informed is
understanding and making proper use of the information you get. 
The National Weather Service issues many diferent types of winter
weather information products.  To get the most of these one must
have an idea of some of the terms used in these products. This
week we will review some winter weather terminology.

If someone says it is going to snow, do they mean a little or a
LOT?  When NWS speaks of the more threatening snow events two
terms they often would use are HEAVY SNOW and BLIZZARD.  

HEAVY SNOW generally means: Snowfall accumulating to 4 inches or
more in depth in 12 hours or less OR; Snowfall accumulating to 6
inches or more in depth in 24 hours or less 

A BLIZZARD means that the following conditions are expected to
prevail for a period of 3 hours or longer:

1. Sustained wind or frequent gusts to 35 miles/hour or greater 
   
2. Considerable falling and/or blowing snow reducing visibility
to less than 1/4 mile 


A few of the Winter Weather Products provided by the NWS offices
during winter months include the following:

A Winter Storm Outlook is a product which may be issued when
there is a good chance of a major winter storm beyond the point
normally covered by a watch (3-5 days). The prime objective of
the outlook is to inform users of the potential of the upcoming
event. 

Winter Weather Advisoriesare are issued for winter weather
situations that cause significant inconveniences but do not meet
warning criteria and, if caution is not exercised, could lead to
life-threatening situations. Advisories are issued for
significant events that are occurring, are imminent, or have a
very high
probability of occurrence. 

A Winter Storm Watch is issued when conditions are favorable for
hazardous winter weather conditions to develop over part or all
of the forecast area, but the occurrence is still uncertain. It
is intended to provide enough lead time so those who need to take
action can do so.  Winter Storm Watches either become Winter
Storm Warnings or advisories or they will be canceled. 

Winter Storm Warnings Heavy Snow Warnings and Ice Storm Warnings
are issued when hazardous winter weather is occurring, imminent,
or highly likely over part or all of the forecast area. They are
reissued whenever there is a change to the timing, areal extent,
or expected condition. (If the event is expected to be limited to
a
specific condition, the forecaster can issue a specific warning
such as Heavy Snow Warning or Ice Storm Warnings,) Warning
statements will include:

  Affected area 
  Potential snowfall amounts, ice accumulations, wind chill, etc. 
  Timing of the event (beginning, ending, time of heaviest
precipitation or worst
         conditions, duration, etc.) 
  Reason the warning was issued. 
  Definition of a warning (especially if the event has not yet
begun) 
  Safety rules, call-to-action statements 
 

SOURCE: Anticipating Hazardous Weather and Community Risk Version
1.0