Climate Highlight for week of September 29th

            This week’s climate highlight deals with determining the average date of the first freeze for four cities located throughout Pennsylvania.  These cities included Scranton, Williamsport, Bradford, and Altoona.  After finding the average date of the first freeze, the data was compared with the long term averages dates to see if there is any correlation between the given years.  The years range from 1898 to 2002.

            The specific years being taken into account during the study were years in which the month of August saw above normal precipitation and overall average temperature.  Going back into our archives of data and with a little help from the National Climatic Data Center, we compiled a list of years where this was the case.  Some of the city data dated back earlier than others, but an overall consensus was reached after compiling all of data.  The consensus being that in years were August saw above average precipitation and temperatures, the first freeze came later on the calendar when compared to normal first freeze dates.

            For example, Scranton usually has its first freeze between October 9th and October 18th.  On years with a wet and warm August, the average first freeze took place on October 22nd.  Williamsport normally sees its first freeze between September 30th and October 8th.  During the wet and warm August’s, our study showed the average first freeze to be on October 18th.  Altoona’s first freeze usually occurs between September 20th and September 29th.  However, October 12th was the average date of first freeze in years where August precipitation and temperatures were above normal.  Bradford was the only city to come close to its average first freeze, due mostly impart to its geographic location.  The normal dates for the first freeze there was between September 14th and September 24th.  In years with a wet and warm August, September 20th was the average first freeze, making Bradford the only city even close to its approximate first freeze.

  A follow up highlight was to determine the first date of measurable snowfall (>.1) for the same locations after a wet and warm August.   In this case, the data was not as uniform leaving room for uncertainty.  Two of the four cities had their first measurable snowfall before the normal first snowfall date.  The other two cities came in after their expected date.   Scranton and Bradford were the cities in which the first measurable snowfall came after the normal date.  Scranton's normal first snowfall is slated on November 8th, while Bradford's was October 20th.  However, Scranton's average first snow in years with a wet and warm August came on November 15th, seven days after the normal date, and Bradford's the 6th, seventeen days after the normal date.  Altoona and Williamsport, on the other hand, received their first snowfall in years with a wet and warm August before their normal date.  The normal date for Altoona is November 20th and the normal date for Williamsport is November 22nd.  The snow fell earlier than expected as Altoona recorded its first snowfall in the respective years on average around the 19th of November, one day before the normal date.  Williamsport registered snowfall before its normal date as well, on average around the 19th of November, three days before its normal date.

-Matt Steinbugl