Dry Start to the Winter

As the fall of 2011 and the beginning of the winter of 2011-12 finishes out as one of the driest time periods on record, the question becomes, how will the rest of the winter finish out?  Will it continue to be dry, or turn snowy and wet?  The time period referred to is the September through December 2011 time period.  The September through December 2011 snowfall total was six tenths of an inch, which ranks lowest of all-time.  This winter season is now on record for going the longest into a season without totaling an inch of snowfall.  The previous record was December 28th of 2006.  The total precipitation (rain and snow) for this same time period was 1.80 inches which ranks as the seventh driest of all-time.  Comparisons were made to our recent four-month dry stretch by looking back in historical records during similar dry stretches since the late 1800s at Aberdeen.  After finding the top driest September through December time periods in snowfall and total precipitation, the rest of the winter and early springs were looked at to determine if the dryness continued.  The two sets of climate data looked at were the top least snowfall and top least total precipitation (rain and snow) during the January through April time periods.  The top twenty driest January through April periods were utilized.  

The snowfall data for the September through December and for the January through April periods showed that the snowfall drought usually continued through the rest of winter as compared to normal.  The snowfall data showed that 15 of the 20 seasons researched had below normal snowfall for the January through April time period.  Two of the January through April periods had near normal snowfall with only three periods receiving above normal snowfall.  Thus, based just on the climate record after a low snowfall September through December time period, 85% of the winters finished out with near or below normal snowfall.  Only 15% of the winters transitioned to above normal snowfall for the January through April time period.  The average January through April snowfall departure from normal was minus 4.1 inches.  Only one winter had above normal snowfall for the entire winter and it was in 1974-75.  Only 2.2 inches of snow had fallen from September through December with 47.7 inches of snowfall from January through April.   The climate data showed that below normal snowfall usually continued after a dry start and it is very difficult to make up the snowfall deficits occurring in late fall and early winter.   The seasonal snowfall departures showed an average departure from normal of minus 15.4 inches.

Average snowfall departures for and after the top 20 driest Sep-Aug time periods

Sep-Dec  Departure  -11.2 inches

Jan-Apr Departure  -4.1 inches

Seasonal Snowfall Departure -15.4 inches

Normal Sep-Dec Snowfall/14.8 inches

Normal Jan-Apr Snowfall 23.6 inches

Normal Seasonal Snowfall/38.4 inches

 

 

Jan-Apr snowfall from normal after the top 20 driest Sep-Dec periods

3/20 Jan-Apr had Above Normal Snowfall or 15%

2/20  Jan-Apr had Near Normal Snowfall or 10%

15/20 Jan-Apr had Below Normal Snowfall or 75%

 

Secondly, the driest total precipitation (rain and snow) September through December time periods were looked at in the climate record and if the dryness continued for January through April.  While just looking at the snowfall, the data showed that snowfall deficits usually continued throughout the rest of the winter.  Although, the total precipitation (overall dryness from September through December) climate data was not as convincing that the dryness would continue.  The total precipitation climate data showed that after a dry start, September through December time period, 50% of the January through April periods continued to be drier than normal while 15% were near normal.  Thirty-five percent of the time periods had above normal total precipitation.  While not as convincing as the snowfall data, the total precipitation data showed that 65% of the seasons, after a dry beginning, finished out with near to below normal precipitation.  Again as was with the snowfall data above, it is difficult to make up the precipitation deficits after a dry start.  The average seasonal precipitation departures were at minus 3.59 inches with minus 4.8 inches of snowfall.  There were no seasons that had above normal precipitation after a dry fall and December with only 5 out of the 20 coming in with above normal snowfall for the entire season.  One thing to note is that of the top seven most driest September through December time periods, 6 of the 7 had near and above normal precipitation and snowfall for the January through April time periods.  Our current dryness ranking is in one of these driest time periods.

Average Precipitation and Snowfall Departures from Normal for and after the top 20 driest

 Sept-Dec periods

Sep-Dec  Precipitation  -3.35 inches

Sep-Dec  Snowfall          -6.1 inches

Jan-Apr  Precipitation    -0.27 inch

Jan-Apr  Snowfall           -1.4 inches

Seasonal Precipitation Departures     -3.59 inches

Seasonal Snowfall Departures            -4.8 inches

 

 

Jan-Apr Precipitation and Snowfall from Normal after the top 20 driest Sep-Dec periods

Normal Jan-Apr Precipitation/4.03 inches

Normal Jan-Apr Snowfall/23.6 inches

7/20 Jan-Apr had Above Normal Precipitation and Snowfall or 35%

10/20 Jan-Apr had Below Normal Precipitation and Snowfall or 50%

3/20 Jan-Apr had Near Normal Precipitation and Snowfall or  15%

 

Seasonal Precipitation and Snowfall from Normal for the top 20 driest Sep-Dec periods

Normal Seasonal (Sep-Apr) Precipitation/9.46 inches

Normal Seasonal (Sep-Apr) Snowfall/38.4 inches

0/20 Seasons had Above Normal Seasonal Precipitation  or 0%

19/20 Seasons had Below Normal Seasonal Precipitation or  95%

1/20 Seasons had Near Normal Seasonal Precipitation or 5%

5/20 Seasons had Above Normal Seasonal Snowfall or  25%

11/20 Seasons had Below Normal Seasonal Snowfall or  55%

4/20 Seasons had Near Normal Seasonal

Snowfall or  20%

 In conclusion, the climate data showed what happened in history after twenty dry starts.  This data showed that the trend is for it to stay dry or move closer to normal both in snowfall and total precipitation.  The climate data also showed that there have been transitions around to wetness after a dry start.  Thus, for the rest of the winter and early spring we will see if we continue with the dryness or we make the switch to a stormy and wet pattern for Aberdeen and surrounding areas. 

 



Return to News Archive

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.