Catlett, Virginia

   * * * * * * * * * *** * **
* * * * * * a white Christmas ? * * * * *
    * * * * * * ** * * * *


It is time again for the annual cavalcade of statistics for Christmas for
the mid-Atlantic region... compiled by the National Weather Service in
Sterling Virginia.

What are the chances for a white Christmas...

What is typical Christmas weather...

Well...

First for Washington... then for Baltimore...


                         *** Washington D.C ***

Examination of weather records going back to 1872 for Washington DC
christmases recorded... shows a typical Christmas day is partly
cloudy with a frosty early morning low of 29 and an afternoon high
of 43. But the year-to-year weather can be anything but typical.

For those who like it cold...

The coldest was 1983... the low temperature was 3 degrees f above
zero /-16c. That day also produced the coldest high temperature for
the day... only a frigid 14 degrees f /-10c that afternoon. The five
coldest lows were:

          1983 - 3 degrees f 1872 - 5 degrees f
          1989 - 11 degrees f 1980 - 12 degrees f
                         1906 13 degrees f

How about a warm Christmas...

The warmest... a toasty 72 degrees (f)/22c in 1964. The warmest low
temperature was 49 degrees (f)/9c in 1987. The 5 warmest christmases:

          1964 - 72 degrees f 1982 - 70 degrees f
          1965 - 69 degrees f 1932 - 68 degrees f
                         1889 65 degrees f

Recent past Christmas day weather:
last year... 2008... a cold front swept across the region shortly
after midnight. The daily high temperature occurred just prior to
the frontal passage. The daytime featured partly sunny skies with
daytime highs in the mid to upper 40s.

      2008 --> hi 58 low 32 partly sunny high occurred at midnight
      2007 --> hi 52 low 37 partly sunny and mild
      2006 --> hi 50 low 37 cloudy with afternoon and night rain
      2005 --> hi 44 low 30 cloudy with afternoon rain
      2004 --> hi 33 low 24 sunny and cold
      2003 --> hi 42 low 31 mostly sunny and blustery
      2002 --> hi 39 low 33 rain with some snow/sleet
      2001 --> hi 41 low 28 mostly sunny and cool
      2000 --> hi 28 low 19 sunny breezy and cold
      1999 --> hi 32 low 21 mostly sunny and cold
      1998 --> hi 36 low 24 sunny and chilly
      1997 --> hi 49 low 40 partly cloudy with rain showers
      1996 --> hi 42 low 29 sunny and cool

For snow lovers...

A white Christmas is a rarity in Washington DC. It happened seven
years ago in 2002 when a generally rainy Christmas morning changed
to snow in midday. There was enough snow to yield a measurable 0.2
tenths of an inch. However... of the past 121 years since 1888 when
snowfall has been measured in Washington DC... only 9 times has there
been measurable snow that actually fell sometime on Christmas day.
That averages to about once every 14 years... or about 7 percent.

The 6 highest snowfalls occurring in Washington on Christmas day...

     1962 ... 5.4"
     1909 ... 4.5"
     1969 ... 4.3"
     1902 ... 1.0"
     1935 ... 0.6"
     1892 ... 0.5"

If you interpret a white Christmas to mean measurable snowfall or
snowfall on the ground... a snow depth of at least one half inch...
that improves the odds some. Since 1888... eighteen times measurable
snow was on the ground on Christmas day that either fell that
day... or was on the ground from a previous storm. That an average of
about once every 7 years... or a 15 percent chance.

In the past 20 years... there have been only two christmases that had
snowfall... 1993 and 2002. Both years featured just a fraction of an
inch. Furthermore... there was only one year in the past 20 that had
an inch or more of snow on the ground on Christmas. That was during
the very cold December of 1989... when nearly 2 inches of snow was on
the ground from previous snowfall that month.

Of note... 16 years ago... in 1993 in a span lasting less than 30
minutes in the evening... 0.2 inch snow fell... with upwards of an
inch falling in the western suburbs. That quick burst of snow on
Christmas night 1993 caused severe travel problems. Much of the snow
melted on contact with paved surfaces as temperatures were just
above freezing at the time the snow fell. However... an Arctic cold
front swept in just after the snow ended. Any water remaining on
roads and sidewalks from melted snow quickly flash froze into a thin
layer of ice... which caused treacherous travel that night.

Precipitation of any sort (rain included) is much easier to come by
of course. Fifty christmases have had measurable precipitation.
That translates to about 36 percent probability of measurable
precipitation... or roughly one third.


                         *** Baltimore ***

Examination of weather records going back to 1872... shows a typical
Christmas day is partly cloudy with a frosty early morning low of 28
and an afternoon high of 43. But the year-to-year weather can be
anything but typical.

For those who like it cold...

The coldest... 1983 when the temperature hit zero degrees f/-18c.
That also produced the coldest high temperature for the day... a
frigid 12 degrees f/-11c that afternoon. The five coldest lows were:

          1983 - 0 degrees f 1980 - 7 degrees f
          1989 - 7 degrees f 1960 - 12 degrees f
                        1998 - 13 degrees f

How about a warm christmas?

The warmest... a toasty 72 degrees f/22c in 1964. That day also produced
the warmest low temperature... 48 degrees f/9c. The 5 warmest christmases:

          1964 - 72 degrees f 1932 - 67 degrees f
          1982 - 70 degrees f 1893 - 67 degrees f
                         1965 65 degrees f

Recent past Christmas day weather:

Last year... 2008... a cold front swept across the region shortly
after midnight. A trace of rain was recorded in Baltimore with the
frontal passage. The daily high occurred just prior to the frontal
passage. The daytime featured partly sunny skies with daytime highs
in the mid to upper 40s.

      2008 --> hi 59 low 32 partly sunny high occurred at midnight
      2007 --> hi 50 low 30 partly sunny and mild
      2006 --> hi 50 low 30 cloudy with afternoon and night rain
      2005 --> hi 42 low 24 cloudy with afternoon rain
      2004 --> hi 31 low 17 sunny and cold
      2003 --> hi 41 low 28 mostly sunny and blustery
      2002 --> hi 38 low 32 rain with some snow/sleet
      2001 --> hi 40 low 23 partly sunny and cool
      2000 --> hi 27 low 17 sunny breezy and cold
      1999 --> hi 32 low 14 mostly sunny and cold
      1998 --> hi 33 low 13 sunny and cold
      1997 --> hi 56 low 41 partly cloudy with rain showers.
      1996 --> hi 38 low 24 sunny and cool.


For snow lovers...

A white Christmas is somewhat of a rarity in Baltimore. Seven years
ago in 2002 a generally rainy Christmas morning changed to snow at
during the late morning. There was enough snow to yield an inch of
snow. However... of the past 116 years since 1893 when snowfall has
been measured in Baltimore MD... only twelve times has there been
measurable snow that fell on Christmas day. That averages out to
about 1 every 10 years... or 10 percent.

The 6 highest snowfalls occurring in Baltimore on Christmas day...

     1909 ... 9.3"
     1969 ... 6.1"
     1902 ... 3.0"
     1962 ... 2.9
     1935 ... 1.2"
     2002 ... 1.0"

If you interpret a white Christmas to mean measurable snowfall or
snow on the ground... at least one half inch... that improves the odds
some. Twenty Nine Times snow was on the ground Christmas day
that either fell that day... or was on the ground from a previous
storm. That gives about a 23 percent chance... or about once every
four years.

However... in the past 20 years there have been only two christmases
that had snow fall that day... 1993 and 2002. Both years featured an
inch or less. Furthermore... there was only two years in the past 20
that had more than an inch of snow on the ground on Christmas. The
most recent of which was during the very cold December of 1989...
when nearly 2 inches of snow was on the ground from previous
snowfall that month.

Precipitation of any sort (rain included) is much easier to come by
of course. Thirty eight christmases have had precipitation. That
translates to about 30 percent probability of measurable
precipitation... or roughly one third.


Happy holidays!!