Los Alamos, February 2004 

(photo by A. Ivey)

Las Vegas, February 2004

(photo by D. Thornburg)

• Winter Storm Watch: A watch is issued to give advance notice when a significant winter storm may affect your area within 12 to 48 hours.  This would include any combination of significant snow or sleet accumulation, significant ice accretion, strong winds, extreme cold, low wind chills, or low visibilities in snow or blowing snow. A winter storm watch is issued when there is at least a 50/50 chance that warning criteria will be met.  Usually the winter storm watch will be upgraded to a warning when the nature and location of the weather event become more apparent. In any case, when a watch is issued for your area, it is time to prepare for severe winter weather.

• Snow Advisory:  A snow advisory is issued whenever accumulating snows are expected to cause localized disruption of travel and other significant inconveniences such as snow covered sidewalks and trails.  Hypothermia and cold exposure may be a threat to anyone ill-prepared or too weak to handle the weather. Reasonable care will help one avoid most cold weather injuries or a fatality.  A snow advisory highlights weather conditions that will cause a significant inconvenience, but if caution is exercised, should not be life-threatening. 

• Winter Weather Advisory:  When a combination of snow, blowing snow, sleet, freezing rain or freezing drizzle is expected to cause localized disruption of travel and result in a significant inconvenience then a winter weather advisory will be issued.  Whereas a snow advisory strictly pertains to snow, a winter weather advisory addresses multiple winter weather hazards.  That is the only difference between the two products.  During the 2004-05 winter season, in lieu of snow advisories, NWS Albuquerque will issue winter weather advisories to cover non life-threatening events. 

• Winter Storm Warning: When conditions that can quickly become life threatening and are more serious than an inconvenience are  imminent or already occurring, a winter storm warning will be issued.  Heavy snows, or a combination of snow, freezing rain or extreme wind chill due to strong wind, may bring widespread or lengthy road closures and hazardous travel conditions, plus threaten temporary loss of community services such as power and water. Deep snow and additional strong wind chill or frostbite may be a threat to even the well dressed individual or to even the strongest person exposed to the frigid weather for only a short period.   

• Heavy Snow  Warning: Issued when only heavy snow will create severe or life-threatening winter conditions. 

• The tables below relate snow depth to minimum warning/advisory thresholds based on the information above and climatology.  The bold numbers represent  mid-point values (rounded up) of the forecasted snow accumulation range for a given storm event during its entire duration.

.

• Blizzard Warning  The most dangerous of all winter storms is the blizzard. In New Mexico,  the northeast highlands and northeast plains are the most blizzard-prone areas where the deadly combination of fierce winds and snow can reduce visibility to near zero and create wind chills well below zero. A blizzard warning is issued when winds of 35 miles an hour will occur in combination with considerable falling and/or blowing snow for at least 3 hours. Visibilities will frequently be reduced to less than 1/4 mile and temperatures are usually 20 degrees Fahrenheit or lower.

• Ice Storm Warning A dangerous coating of ice, usually 1/4 inch or more. Ice storms are rare if not unheard of west of the Rio Grande Valley.  However, across eastern New Mexico  a mixture of freezing drizzle,  freezing rain and light snow is not uncommon whenever arctic air masses invade the plains.  In most cases, ice accumulations are less than 1/4 inch and a winter weather advisory is issued.  

• Wind Chill Warning is issued when the wind chill temperatures at or colder than minus 50 degrees F.  At this level, frostbite can occur on exposed flesh within minutes.   As the wind chill temperature drops, the frostbite time decreases, especially with higher wind speeds.

• Note: Strong winds, usually blowing from the northwest or north, often develop in the wake of winter storms that cross New Mexico.  This is especially true along the east slopes of the Central Mountain Chain and high plains of central and northeast New Mexico. These strong and gusty winds can persist hours after the precipitation has ended creating areas of reduced visibilities in blowing snow.

.

• a WATCH means it's time to get ready,
• an ADVISORY means inconvenience,
• and a WARNING means the situation is life-threatening.

...

Frequency of Snow Events Across New Mexico