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Climate of 2004/2005 Northern Hemisphere Winter Season: Snow and Ice National Climatic Data Center, 14 June 2005

Late Season and Seasonal Summary

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The map to the left depicts the percent of average seasonal snowpack across the western U.S. as of May 1st. Despite some much needed rain and snow for the Pacific Northwest during spring (March-May), snowpack and snow water content in the Northwest still reflected the lack of winter precipitation with areas of Washington and Oregon having less than 25% of their normal snow. The Southwest maintained an above average snowpack during the snow season with some areas (central Sierra Nevada, parts of Utah) over 125% of normal, even at the end of May. This was mostly due to a series of Pacific storms impacting the region through the winter. Interior Alaska also had above average snowpack, while the northern and southern coasts of the state received less than average snow for the 2004-2005 snow season.

Parts of Europe and Asia had colder-than-average conditions and large snow accumulations during the winter and spring, including more than 6 feet (2 meters) of snow in March in Serbia and Montenegro, and along the northern shores of the Mediterranean in February. In the U.S., late season snow fell in Colorado during April, leaving well over 2 feet of snow in Denver and surrounding mountain areas (image right). The Great Lakes south to the southern Appalachians also received snowfall during the last week of April, leaving over a foot of accumulation in parts of Ohio.

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March

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The map to the left depicts the percent of average seasonal snowpack across the western U.S. as of April 1st. Despite some much needed rain and snow for the Pacific Northwest during March, snowpack was still much below average for the season, with areas of Washington and Oregon having less than 50% of their normal snow. The Southwest maintained an above average snowpack during March with many areas over 150% of normal. This was mostly due to a series of Pacific storms impacting the region through the winter. Interior Alaska also had above average snowpack, while the northern and southern coasts of the state received less than average snow for the 2004-2005 winter season.

February

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The map to the left depicts the percent of average seasonal snowpack across the western U.S. as of March 1st. In stark contrast to well above average snowpack in the Southwest, the Northwest has had below average snowfall this snow season and this is reflected in the lower snowpack percentages. As reported by the USDA, several individual stations in the remote high altitude SNOTEL network set new record lows (in the north) and highs (in the south) for both snow water content and water-year-to-date accumulated precipitation. Many stations in the Pacific Northwest and northern Rockies shattered snow water content records set during the record dry 1976-77 winter. Snowpack conditions in Alaska were generally above normal in the interior regions, below normal in coastal areas.

January

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The map to the left depicts the percent of average seasonal snowpack across the western U.S. as of February 1st. In stark contrast to well above average snowpack in the Southwest, the Northwest has had below average snowfall this snow season and this is reflected in the lower snowpack percentages. Much of the West is reliant on winter precipitation to refill reservoirs in preparation for the higher summer water demand. It is the 6th year of drought in parts of the northern Rockies and High Plains. However, record-breaking snow fell during late December and early January in parts of the southern West. A series of storms that also led to devastating rain and flood damage in southern California, left well over 10 feet of snow in the higher locations of the Sierra Nevada. Even areas below 7000 ft in the Sierra received snowfall totalling 4-6 feet in accumulation. Nevada, northern Arizona and Utah also received much above average snowfall for the month and percent of seasonal snowpack was over 150% in some parts of the southern West at the end of January.

Sea ice increased across the Great Lakes in January 2005 with Lake Erie being almost completely ice-covered and Lake Ontario remaining ice-free only in the center of its surface. Lakes Huron, Superior and Michigan still had substantial ice-free areas in early February, though lake-surface temperatures were below 40�F across all lakes. Northern Hemisphere January sea-ice extent was the lowest on record for the month in 2005, with an area of 14.8 million km2. Satellites have been able to estimate sea ice extent since 1978 and the trend in January Northern Hemisphere sea ice extent since 1979 is -2.9% per decade (data and graphic courtesy of the National Snow and Ice Data Center).

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December

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As can be seen in the animated image to the left, several significant snow storms affected the continental U.S. during December while most of Canada was snow-covered for the entire month. Sea ice increased over Hudson Bay and water bodies in the Canadian interior, while the Great Lakes remained ice-free during December. A notable snow event was captured in the image to the left as snow fell in southern Texas over the Christmas holiday. Over a foot was recorded in Victoria, Texas, while Brownsville, at the southern tip of the state, received 1.5 inches. A snow storm that impacted the Ohio Valley on the 22nd and 23rd caused parts of Indiana and Kentucky to receive more than their average seasonal total in just one day. More information is also available on NCDC's December Hazards page.

November

As can be seen in the animated image to the right, snow extent further increased across North America during November, with anomalously sustained snow cover for the time of year in west-central Canada and parts of the western U.S., with less than average snow cover through the month in the upper Midwest. A major snowfall event occurred across areas of the West over the Thanksgiving weekend on the 28th and 29th. More details on November snowfall will be available in the coming days.

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October

As can be seen in the animated image to the right, snow extent increased across North America during October, with anomalously sustained snow cover for the time of year in central and western Canada, and less than average snow cover for eastern Canada and southwestern Alaska. The first major snowfall of the season occurred for areas of the West as two large storms brought heavy snow to some western states, including California. Snow water content was also above average for basins in Wyoming, Montana and New Mexico at the end of October.

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The graphs to the left show snow cover extent and departures from average for the contiguous US (top) and Alaska (bottom). Despite the advance of continental snow cover during October (as can be seen from the red line), snow cover extent was still below average for both Alaska and the contiguous US for the month (shown by the blue bars). Alaska had 51,000 km2 less snow cover than average, while the contiguous US had -92,000 km2 less than the mean. However, snow cover across Canada was greater than the October average leading to a positive anomaly of 550,000 km2 for the whole of North America. (Averages are calculated based on data from Nov 1966 to present).

The image to the right shows a MODIS satellite image taken on October 31st from NASA's Terra satellite. Snow is visible on the Sierra Nevada Mountains of California following the second major storm in as many weeks to hit the state. Several feet of snow fell in some mountain locations and ski-resorts were able to open early.

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Early Season

Snow cover extent began to increase in the northern areas of North America as can be seen in the animated image to the right. Some early season snowfall also occurred in the Canadian and U.S. Rockies. Anchorage, Alaska had its highest September snowfall on record (6 inches), all of which fell in one day (September 25th), also breaking the old record for the heaviest 24-hour snowfall for the month of September in Anchorage.

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Although some early snow fell in parts of the western mountains, monthly snow cover extent for the contiguous U.S. was near zero square kilometers as can be seen in the graph to the left. For September, the average snow cover extent is approximately 12,000 square kilometers for the nation, with an additional 184,000 km2 for Alaska. Alaska also had below average snow cover for September with 97,000 km2 less than average.

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