Winter Weather Preparedness Week Message 1
By Gannon Medwick
Monday, December 01, 2008
Though snowflakes flew across Eastern Carolina in November, the heart of the winter season is still weeks away. This week is “Winter Weather Preparedness Week” in North Carolina, and the National Weather Service Forecast Office in Raleigh has prepared this information-rich message to start the week off:
OUTLOOK FOR THIS WINTER
CENTRAL NORTH CAROLINA HAS BEEN SPARED THE IMPACT OF SIGNIFICANT WINTER WEATHER OVER THE LAST SEVERAL YEARS. IN FACT THE LAST WINTER STORMS TO STRIKE THE AREA OCCURRED BACK DURING THE WINTER OF 2004 AND 2005. THE LACK OF WINTER WEATHER IN 2007 AND EARLY 2008 WAS IN PART DUE TO LA NINA, DEFINED AS COOLER THAN NORMAL SEA SURFACE TEMPERATURES IN THE EQUITORIAL PACIFIC OCEAN. LA NINA CREATED A SHIFT IN THE WEATHER PATTERNS RESULTING IN BELOW NORMAL PRECIPITATION. HOWEVER LA NINA HAS LOST ITS GRIP AND WEATHER PATTERNS ARE RETURNING TO NEAR NORMAL. COULD THIS MEAN A RETURN TO A MORE NORMAL WINTER WITH MORE SNOW, ICE AND WINTER STORM ACTIVITY? IT IS VERY DIFFICULT TO PREDICT HOW MANY IF ANY WINTER STORMS WILL IMPACT NORTH CAROLINA THIS UPCOMING WINTER, BUT A RETURN TO NEAR NORMAL TEMPERATURES AS WELL AS NEAR NORMAL PRCIPITATION AND SOME OF THIS PRECIPITATION COULD FALL IN THE FORM OF SNOW, SLEET AND FREEZING RAIN. PREPARATION FOR WINTER STORMS IS OF MORE IMPORTANCE THIS YEAR SINCE IT HAS BEEN SEVERAL YEARS SINCE A MAJOR WINTER STORM HAS AFFECTED CENTRAL NORTH CAROLINA. EVERYONE SHOULD USE THIS WEEK TO LOOK AHEAD TO THE UPCOMING WINTER MONTHS AND PREPARE FOR THE POSSIBILITY OF WINTER STORMS. BELOW ARE SOME DEFINITIONS OF VARIOUS WINTER PRECIPITATION TYPES…AS WELL AS INFORMATION ON NWS WINTER STORM WARNINGS AND ADVISORIES.
WINTER PRECIPITATION TERMS
FREEZING RAIN IS RAIN THAT FALLS AND FREEZES TO A COLD SURFACE SUCH AS A ROAD OR TREE, CAUSING A GLAZE OF ICE TO FORM. FREEZING RAIN FORMS WHEN SNOW FALLS THROUGH A WARM LAYER ABOVE THE GROUND, MELTS TO RAIN, THEN RE-FREEZES UPON REACHING THE GROUND, WHERE THE AIR AND GROUND-LEVEL OBJECTS ARE BELOW FREEZING. FREEZING RAIN OR “ICE STORMS” CAN BRING DOWN TREES AND POWER LINES, AND SEVERELY HAMPER TRAVEL. THE ICE STORM IN DECEMBER OF 2002 CRIPPLED CENTRAL NORTH CAROLINA LEAVING SOME AREAS WITHOUT POWER FOR A WEEK.
SLEET IS RAIN THAT HAS RE-FROZEN INTO ICE PELLETS PRIOR TO REACHING THE GROUND. SLEET FORMS IN A SIMILAR MANNER TO FREEZING RAIN. HOWEVER, THE LAYER OF COLD AIR NEAR THE GROUND IS THICK ENOUGH TO ALLOW THE RAIN DROPS TO RE-FREEZE BEFORE REACHING THE GROUND. SLEET WILL BOUNCE WHEN IT STRIKES A HARD SURFACE. SLEET CAN ACCUMULATE LIKE SNOW AND MAKE A ROAD SLICK, BUT IT IS NOT AS HAZARDOUS AS FREEZING RAIN.
A BLIZZARD OCCURS WHEN WINDS 35 MPH OR GREATER COMBINE WITH FALLING OR BLOWING SNOW TO REDUCE VISIBILITY TO OR BELOW ONE QUARTER MILE CAUSING WHITE-OUT CONDITIONS. PEOPLE OUT IN BLIZZARDS CAN QUICKLY BECOME DISORIENTED FROM THE COLD, SNOW AND WIND, AND LOSE THEIR WAY WHEN ONLY SEVERAL YARDS FROM THEIR HOME OR CAR.
THE TERM FLURRIES REFERS TO VERY LIGHT SNOW OR SNOW THAT OCCURS FOR A SHORT TIME PERIOD ONLY CAUSING A LIGHT DUSTING AT BEST.
WIND CHILL TEMPERATURE IS THE “FEEL-LIKE” TEMPERATURE DENOTING THE COMBINED EFFECT OF WIND AND TEMPERATURE ON PEOPLE AND ANIMALS. WIND CHILL IS BASED ON THE RATE OF HEAT LOSS FROM EXPOSED SKIN. WEARING LAYERS OF CLOTHING WILL HELP RETAIN YOUR BODY HEAT AND COMBAT WIND CHILL. ONCE WIND CHILL TEMPERATURES DROP BELOW -20 DEGREES F, EXPOSED FLESH CAN FREEZE IN 30 MINUTES OR LESS, CAUSING FROST BITE.
WINTER STORM WATCHES AND WARNINGS
WATCHES AND WARNINGS ARE ISSUED BY THE NATIONAL WEATHER SERVICE FOR POTENTIALLY LIFE-THREATENING CONDITIONS. IN WINTER, WATCHES AND WARNINGS ARE ISSUED FOR SIGNIFICANT SNOW AND/OR ICE STORMS. BELOW ARE A LIST OF WINTER WEATHER WATCHES AND WARNINGS.
WINTER STORM WATCH: A WINTER STORM WATCH IS ISSUED WHEN THE FOLLOWING WEATHER CONDITIONS ARE POSSIBLE WITHIN 24 TO 48 HOURS: AT LEAST 3 TO 5 INCHES OF SNOW AND/OR ICE ACCUMULATIONS OF 1/4 INCH OR MORE…IN A 12 TO 24 HOUR PERIOD.
WINTER STORM WARNING: A WINTER STORM WARNING IS ISSUED WHEN THE WATCH CONDITIONS DESCRIBED ABOVE ARE EITHER IMMINENT OR LIKELY WITHIN 24 HOURS.
BLIZZARD WARNING: A BLIZZARD WARNING IS ISSUED WHEN STRONG WINDS COMBINE WITH FALLING AND/OR BLOWING SNOW TO REDUCE VISIBILITY TO ONE QUARTER MILE OR LESS FOR AT LEAST 3 HOURS. DEEP SNOW DRIFTS AND DANGEROUSLY LOW WIND CHILLS OFTEN ACCOMPANY BLIZZARD CONDITIONS.
WIND CHILL WARNING: A WIND CHILL WARNING IS ISSUED WHEN WIND CHILL TEMPERATURES ARE FORECAST TO REACH 20 DEGREES BELOW ZERO OR COLDER.
WINTER WEATHER ADVISORY: A WINTER WEATHER ADVISORY IS ISSUED WHEN A COMBINATION OF SNOW, SLEET OR FREEZING RAIN PRECIPITATION WILL CAUSE SIGNIFICANT INCONVENIENCE AND HAZARDOUS DRIVING CONDITIONS. WEATHER ADVISORIES ARE ISSUED FOR HAZARDOUS…BUT NOT NECESSARILY LIFE-THREATENING CONDITIONS. WINTER STORMS ARE DECEPTIVE KILLERS BECAUSE MOST DEATHS ARE INDIRECTLY RELATED TO THE STORM. EXAMPLES ARE TRAFFIC ACCIDENTS DUE TO ICY ROADS…HEART ATTACKS WHILE SHOVELING SNOW…OR DEATHS DUE TO PROLONGED EXPOSURE TO THE COLD.
THE ADVISORIES, WATCHES AND WARNINGS LISTED ABOVE ARE ISSUED TO HELP YOU PREPARE FOR UPCOMING WINTER WEATHER AND TAKE APPROPRIATE ACTION TO PROTECT YOURSELF AND YOUR PROPERTY.
Thanks for checking out my weather blog!
Gannon Medwick
Storm Team 9 Meteorologist
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