PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE LITTLE ROCK AR
600 AM CST TUE NOV 17 2015

...WINTER PRECIPITATION TYPES...

NOVEMBER 16TH THROUGH 20TH IS WINTER WEATHER AWARENESS WEEK IN ARKANSAS. PEOPLE
 ARE ASKED TO TAKE SOME TIME TO PREPARE FOR  THE UPCOMING WINTER SEASON.

TODAYS TOPIC IS WINTER PRECIPITATION TYPES.

SNOW -- SNOW FORMS IN THE CLOUDS AND REMAINS AS SNOW ALL THE WAY TO THE GROUND.
 IT MOST COMMONLY TAKES THE FORM OF SNOWFLAKES...WHICH ARE THE FAMILIAR
SIX-SIDED ICE CRYSTALS. IT MAY ALSO FALL IN THE FROM OF SNOW PELLETS OR SNOW
GRAINS.

SNOW FLURRIES ARE NORMALLY SEEN AS A FEW SNOWFLAKES FALLING... ALTHOUGH
VISIBILITIES CAN BE REDUCED AT TIMES. IN ARKANSAS...THE TERM SNOW FLURRIES IS
USED TO INDICATE THAT NO ACCUMULATION IS  EXPECTED.

SNOW SHOWERS IS A TERM NOT OFTEN USED IN ARKANSAS. IN THIS TYPE OF
PRECIPITATION...THE SNOW FALLS AT VARYING INTENSITIES...OFTEN  CHANGING
INTENSITIES OVER BRIEF PERIODS. ACCUMULATION MAY OCCUR... ESPECIALLY DURING
MODERATE TO HEAVY SNOW SHOWERS.

BLOWING SNOW REFERS TO SNOW THAT IS ALREADY ON THE GROUND AND IS  LIFTED INTO
THE AIR BY THE WIND.

IN ARKANSAS...HEAVIER SNOWS USUALLY OCCUR WHEN COLD AIR IS ALREADY IN PLACE
OVER THE STATE AND A STRONG UPPER LEVEL LOW  PRESSURE SYSTEM MOVES OUT OF THE
SOUTHWESTERN UNITED STATES. THE  LOW SERVES TO PULL MOIST AIR FROM THE GULF OF
MEXICO NORTHWARD INTO  THE COLD AIR. LIGHT SNOW OR SNOW FLURRIES CAN ALSO OCCUR
 IN THE COLD  AIR THAT FOLLOWS THE PASSAGE OF AN ARCTIC COLD FRONT.

SLEET -- SLEET CONSISTS OF PELLETS OF ICE. IN FACT...FOR PEOPLE WHO HAVE
TROUBLE WITH THE DIFFERENCE BETWEEN SLEET AND FREEZING RAIN... IT MAY BE EASIER
 TO ASSOCIATE SLEET WITH ITS TECHNICAL NAME...WHICH IS ICE PELLETS. FOR SLEET
TO FORM...SNOW BEGINS FALLING FROM THE CLOUDS BUT THEN GOES THROUGH A LAYER OF
ABOVE-FREEZING AIR THOUSANDS OF FEET ABOVE THE GROUND. THIS CAUSES THE SNOW TO
CHANGE TO RAIN.  THEN...THE RAIN GOES THROUGH A LAYER OF BELOW-FREEZING
AIR...USUALLY AT LEAST TWO TO THREE THOUSAND FEET THICK...AND THE PRECIPITATION
  TURNS INTO PELLETS OF ICE.

SLEET TYPICALLY OCCURS IN A FAIRLY NARROW BAND. THIS BAND USUALLY MOVES...BUT
AT TIMES MAY REMAIN NEARLY STATIONARY...RESULTING IN ACCUMULATIONS OF SLEET.

IN ARKANSAS...SLEET MOST COMMONLY OCCURS IN A NARROW BAND BETWEEN AN AREA OF
RAIN TO THE SOUTH AND AN AREA OF SNOW TO THE NORTH.

FREEZING RAIN -- THIS WEATHER PHENOMENON IS SOMETIMES CALLED GLAZE... BECAUSE
OF THE GLAZE OF ICE IT PUTS ON SURFACES AT THE GROUND. FREEZING RAIN NORMALLY
OCCURS WHEN PRECIPITATION FALLS FROM THE  CLOUDS AS SNOW...THEN GOES THROUGH AN
 ABOVE-FREEZING LAYER...WHICH  TURNS THE PRECIPITATION TO RAIN. THEN...THE RAIN
 REACHES THE GROUND  WHERE TEMPERATURES ARE BELOW FREEZING. THE RAIN THEN
FREEZES AS IT  HITS EXPOSED OBJECTS. IN THE WORST CASES...EVERYTHING BECOMES
COATED  WITH A LAYER OF ICE.

IN ARKANSAS...FREEZING RAIN COMMONLY OCCURS AS AN ARCTIC HIGH  PRESSURE SYSTEM
BEGINS TO MOVE AWAY FROM THE STATE. IN THIS  SITUATION...COLD AIR IS STILL
LINGERING AT THE GROUND...BUT WARMER  SOUTHERLY WINDS FROM THE GULF OF MEXICO
BEGIN BRINGING MOISTURE BACK  OVER THE TOP OF THE COLD AIR. SINCE THE AIR AT
THE GROUND HAS NOT  WARMED ABOVE FREEZING...THE RAIN THAT FALLS FREEZES ON THE
GROUND  AND OTHER OBJECTS. FREEZING RAIN...AND ITS COUSIN FREEZING DRIZZLE...
OFTEN DEVELOP DURING THE LATE NIGHT HOURS...CREATING ICY CONDITIONS  FOR
MORNING RUSH HOUR.

FREEZING FOG -- WHILE THIS IS NOT PRECIPITATION FALLING FROM THE  CLOUDS...IT
IS ANOTHER WINTER WEATHER HAZARD. FREEZING FOG TYPICALLY DEVELOPS ON
CLEAR...CALM NIGHTS WHEN TEMPERATURES ARE BELOW FREEZING. FOG FORMS AND
FREEZES...USUALLY ON BRIDGES...OVERPASSES...AND OTHER ELEVATED ROADWAYS. IT CAN
 CREATE QUITE A SURPRISE FOR MOTORISTS...DUE TO THE PRESENCE OF CLEAR SKIES
OVERHEAD.

FROST -- FROST DESCRIBES THE FORMATION OF THIN ICE CRYSTALS ON THE GROUND OR
OTHER SURFACES IN THE FORM OF SCALES...NEEDLES... FEATHERS...OR FANS. FROST
FORMS WHEN WATER VAPOR IN THE AIR TURNS  DIRECTLY TO ICE CRYSTALS ON AN OBJECT.
 THE TEMPERATURE OF THE OBJECT  MUST BE BELOW FREEZING FOR FROST TO OCCUR.
HOWEVER...FROST IS  SOMETIMES SEEN ON THE GROUND WHEN OFFICIAL TEMPERATURES ARE
 REPORTED  TO BE ABOVE FREEZING. THIS IS BECAUSE THE OFFICIAL TEMPERATURE IS 
TAKEN ABOUT FIVE FEET ABOVE THE GROUND...WHERE THE AIR CAN BE A FEW  DEGREES
WARMER THAN THE TEMPERATURE AT GROUND LEVEL.

$$




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