NOAA's National Centers for Environmental Information
At the beginning of April, 13.9 percent of the contiguous U.S. had snow on the ground, and was confined to the mountainous West, northern New England, and parts of New York state. April was warmer and drier than normal for most of the eastern U.S., which limited snow accumulations during the month. According to the Rutgers Global Snow Lab, a NOAA supported facility, the U.S. snow extent for April 2010 ranked as ninth smallest in the 44 year satellite record at 434,000 square miles (1.1 million square km)—312,000 square miles (0.8 million square km) below the long–term average of 746,000 square miles (1.9 million square km). The low extent is partially attributable to the warm temperatures for March and April across the northern tier of the country melting the snow that fell during the winter season (December 2009–February 2010) and limiting any additional accumulations. By the end of April, 10.3 percent of the contiguous U.S. as under snow —the high terrain of the West and a portion of New York, Vermont, New Hampshire, and Maine as the snow from a late season storm remained on the ground.
April North American Snow Cover Anomalies
The average North American snow cover extent in April was also very low compared to normal—11.0 million square miles (28.5 million square km), which is 2.2 million square miles (5.7 million square km) below the April mean of 13.2 million square miles (34.2 million square km). The April 2010 snow extent is the smallest April value since the satellite record began in 1966, and is smaller than two May extents that have occurred in the past (May 1974 and May 1985). The anomaly of 2.2 million square miles (5.7 million square km) is the largest negative anomaly to occur in the 521 months that satellite measurements are available. It is interesting to note that in December 2009 (four months prior), the North American snow cover extent was at a monthly record high, with January and February 2010 also having much above average snow cover. Although the snow cover was expansive during the winter, the snow depths were anomalously low. Very warm temperatures during March and April across the northern U.S. and most of Canada led to a great deal of snow melt. The combination fo warm spring temperatures and shallow snowpacks both contributed to the North American record–low snow extent for April. Please see the 2009–2010 Cold Season Special Report for additional informaton.
Arctic Sea ice extent was near the long–term average during the month, marking the largest April extent since 2001. The ice extent averaged 5.67 million square miles (14.69 million square km) for April, 120,000 square miles (310,000 square km) below the 1979–2000 average. The rate of ice extent decline for the month was 16,000 square miles per day (41,000 square km), which is also near normal. The late season growth spurt of the ice in March (see March snow and ice report), delayed the typical start of the melting by a month. This late start to the melt season was a significant factor in the near–normal April ice extent. Please see the Arctic Sea ice analysis by the National Snow and Ice Data Center for additional information.
A rare, late–season snow storm brought significant snow accumulations to parts of New England and Upper New York State the last week of April. Over 20 inches (50.8 cm) of snow were reported in Vermont’s Green Mountains. Snowfall reports greater than a foot (30.5 cm) were widespread. Daily snowfall records were broken at the Burlington International Airport on the 27th and 28th, with the city receiving 5.5 inches (14 cm) for the entire event. At the peak of the storm nearly 30,000 homes were without power in the region (Source: AP).