How Late Was This First Appreciable Snowfall?

 

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE CHICAGO IL
227 AM CST FRI JAN 13 2012 /327 AM EST FRI JAN 13 2012/
...A LATE SEASON FIRST APPRECIABLE SNOWFALL...
THIS WINTER SEASON HAD A REMARKABLY SLOW START TO IT THROUGH THE
FIRST WEEK AND A HALF OF JANUARY...WITH BOTH LITTLE SNOW AND MILD
TEMPERATURES. THERE HAD YET TO BE A SINGLE TWO INCH SNOW EVENT IN
EITHER CHICAGO OR ROCKFORD THROUGH THAT TIME. AFTER ONE FINAL
VERY MILD DAY IN THE 50S ON JANUARY 11TH...TEMPERATURES PLUNGED
AND SNOW OVERSPREAD THE AREA ON JANUARY 12TH. WIDESPREAD SNOWFALL
AMOUNTS OF 4 TO 7 INCHES WERE SEEN ACROSS THE AREA DURING THE
CALENDAR DAY OF THE 12TH. THE FOLLOWING STATISTICS ATTEMPT TO PUT
INTO PERSPECTIVE HOW LATE OF A START THIS WAS FOR A FIRST
APPRECIABLE EVENT.
.CHICAGO...
4.7 INCHES OF SNOW WAS OFFICIALLY MEASURED AT CHICAGO O`HARE
INTERNATIONAL AIRPORT ON JANUARY 12TH. FOR THE 2011-2012 WINTER
SEASON...THIS WAS THE FIRST EVENT THAT PRODUCED AT LEAST TWO
INCHES OF SNOWFALL. THROUGH THE PAST ONE HUNDRED YEARS...THE
AVERAGE DAY WITH TWO INCHES OF SNOW AT CHICAGO IS DECEMBER 16TH. IN
THAT TIME...THERE HAVE ONLY BEEN ELEVEN WINTERS TO SEE A FIRST TWO
INCH PLUS SNOW IN A DAY LATER THAN THE 2011-2012 WINTER. THERE
HAVE ONLY BEEN FOUR WINTERS SINCE 1940 /RETURN FREQUENCY OF ONCE
EVERY 18 YEARS/. THIS LATE OF A FIRST TWO INCH SNOWFALL HAD NOT
BEEN SEEN SINCE THE 2001-2002 WINTER...WHEN THE FIRST TWO INCH
PLUS EVENT MATERIALIZED ON JANUARY 16TH 2002. THE LATEST IN THE
PAST ONE HUNDRED YEARS WAS DURING THE 1930-1931 WINTER...WHEN THE
FIRST TWO PLUS INCH EVENT DID NOT OCCUR UNTIL MARCH 7 1931.
.ROCKFORD...
THE JANUARY 12TH CALENDAR DAY BROUGHT 4.5 INCHES OF SNOW OFFICIALLY
AT ROCKFORD. THIS WAS THE FIRST EVENT WITH AT LEAST TWO INCHES OF
SNOWFALL THIS SEASON. LOOKING BACK SINCE 1940..THE AVERAGE FIRST
CALENDAR DAY WITH TWO INCHES OF SNOW IN ROCKFORD DURING A WINTER
SEASON IS DECEMBER 7TH. IN THOSE PAST 71 YEARS...THERE HAVE ONLY
BEEN THREE WINTERS TO SEE A FIRST TWO INCH PLUS SNOW IN A DAY
LATER THAN THE 2011-2012 WINTER /RETURN FREQUENCY OF ONCE EVERY 24
YEARS/. THIS LATE OF A FIRST TWO INCH SNOWFALL HAD NOT BEEN SEEN
SINCE THE 2001-2002 WINTER...WHEN THE FIRST TWO INCH PLUS EVENT
MATERIALIZED ON JANUARY 16TH 2002. THE LATEST SINCE 1940 WAS
DURING THE 1980-1981 WINTER...WHEN THE FIRST TWO INCH PLUS EVENT
DID NOT OCCUR UNTIL FEBRUARY 10 1981.
$$
MTF


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