Winter Weather Terminology
Here is some useful information from the NWS office in Mt. Holly, NJ.
NATIONAL WEATHER SERVICE WINTER FORECAST TERMINOLOGY.
FREEZING RAIN: RAIN THAT FREEZES UPON CONTACT WITH A COLD SURFACE.
SLEET: SOLID GRAINS OF ICE THAT FORM FROM RAIN THAT FREEZES BEFORE
REACHING THE GROUND. THESE PELLETS OF ICE TEND TO BOUNCE UPON CONTACT
AND MAY ACCUMULATE ENOUGH TO COVER THE GROUND...EVEN TO A DEPTH OF
SEVERAL INCHES.
SNOW SQUALL: AN INTENSE FALL OF ACCUMULATING SNOW...REDUCING VISIBILITY
SIGNIFICANTLY AND OFTEN ACCOMPANIED BY INCREASED WINDS.
HEAVY SNOW: 8 INCHES OR MORE OF SNOW IN 24 HOURS ACROSS PENNSYLVANIA FOR
WIDESPREAD SNOW AND 6 INCHES IN 12 HOURS FOR LAKE EFFECT SNOW.
JUST AS WITH SUMMER WEATHER...THE NATIONAL WEATHER SERVICE ISSUES A
WATCH TO ALERT THE PUBLIC OF THE POTENTIAL FOR SEVERE WINTER WEATHER.
A WINTER STORM WATCH MEANS CONDITIONS EXIST FOR THE POSSIBLE OCCURRENCE
OF SEVERE WINTER WEATHER SUCH AS BLIZZARD CONDITIONS...HEAVY
SNOW...SIGNIFICANT FREEZING RAIN OR HEAVY SLEET. A WATCH IS USUALLY
ISSUED 24 TO 48 HOURS IN ADVANCE OF THE WINTER STORM.
A WINTER STORM WARNING IS ISSUED WHEN HEAVY SNOW...SIGNIFICANT FREEZING
RAIN...OR HEAVY SLEET IS EXPECTED TO OCCUR. USUALLY ISSUED 6 TO 18 HOURS
IN ADVANCE OF THE STORM. NORMALLY A WARNING IS ISSUED AFTER A WINTER
STORM WATCH HAS BEEN IN EFFECT. IF A WINTER STORM DEVELOPS QUICKLY THEN
THE WARNING MAY NOT HAVE BEEN PRECEDED BY A WATCH.
A BLIZZARD WARNING IS ISSUED WHEN SUSTAINED OR GUSTY WINDS OF 35 MPH OR
MORE ARE EXPECTED TO REDUCE VISIBILITY AT OR BELOW A QUARTER OF A MILE
DUE TO FALLING OR BLOWING SNOW FOR AT LEAST THREE HOURS.
WIND CHILL WARNINGS ARE ISSUED FOR WIND CHILLS BELOW -25 DEGREES
FAHRENHEIT.
A LESS SEVERE WINTER WEATHER EVENT WILL PROMPT THE ISSUANCE OF AN
ADVISORY. AN ADVISORY IS NAMED SPECIFIC TO THE WEATHER EVENT EXPECTED
AND ISSUED WHEN THE EVENT IS EXPECTED TO BE WIDESPREAD.
TRAVEL BY FOOT OR VEHICLE MAY BE DANGEROUS DURING AN ADVISORY EVEN IF
THE WINTER WEATHER IS NOT EXPECTED TO REACH WINTER STORM CRITERIA. SOME
EXAMPLES OF ADVISORIES:
WINTER WEATHER ADVISORY FOR SNOW MEANS SNOWFALL WITHIN 12 HOURS AN
AVERAGE OF 3 INCHES OR MORE OF SNOW IS EXPECTED IN CENTRAL PENNSYLVANIA.
WINTER WEATHER ADVISORY FOR FREEZING RAIN MEANS A GLAZE OF ICE EXPECTED
FROM FREEZING RAIN THAT WILL HAMPER TRAVEL IS EXPECTED TO OCCUR.
WIND CHILL ADVISORY MEANS WIND CHILL TEMPERATURES ARE EXPECTED TO BE
AROUND 15 BELOW ZERO FOR AN EXTENDED TIME.
DENSE FOG ADVISORY IS ISSUED WHEN DENSE FOG IS FORECAST TO FORM THAT
REDUCES VISIBILITY TO LESS THAN ONE QUARTER OF A MILE.
WINTER WEATHER ADVISORY: ISSUED WHEN TWO OR MORE OF THE ABOVE ADVISORY
CONDITIONS ARE EXPECTED.
KNOWING WINTER WEATHER TERMS PROVIDES YOU WITH USEFUL INFORMATION FOR
PLANNING AND SAFETY PURPOSES.