Snowfall map of the February 1973 United States blizzard, a Category 4 winter storm, outlining the thresholds for Regional Snowfall Index in the Southeast and showing the different regions assessed using the scale

The Regional Snowfall Index (RSI) is a system used by NOAA to assess the societal impacts of winter storms in the United States. The scale is a replacement for the Northeast Snowfall Impact Scale (NESIS) system, which was used for winter storms just in the Northeastern United States; Regional Snowfall Index assesses winter storm impacts in the six easternmost regions of the United States instead of just the Northeast. Since its initiation, the NCDC has assigned RSI values to nearly 600 winter storms since 1900.

Storms are ranked from Category 0 "Nuisance" to Category 5 "Extreme" on the scale. A Category 4 winter storm on the RSI scale is classified as "Crippling". The impact of the storms is assessed in six different regions of the United States: the Northeast, Northern Rockies and Plains, Ohio Valley, South, Southeast, and Upper Midwest.[1] A Category 4 "Crippling" ranking is indicated by a numerical score between 10 and 18 on the scale.

Out of the nearly 600 historical winter storms assessed since 1900, only 74 storms have been given a Category 4 or above ranking, 48 of which were Category 4 storms. The highest ranking Category 4 winter storm is the March 2–8, 1915 United States blizzard, which had an RSI of 17.67. The most recent storm to receive a Category 4 ranking is the December 2022 North American winter storm, which scored an RSI value of 11.49. The following list orders the Category 4 storms chronologically.[1][2][3]

List of Category 4 events

This list includes all winter storms which had a maximum RSI value in the Category 4 range. Storms that ranked as a Category 4 in some regions but ranked as a Category 5 in one or more other regions are not included in this list.[4][2]

Year Date Max. RSI Region
1900 February 26 – March 3 15.65 Northeast, South
1902 February 13–19 10.16 Southeast
1902 March 3–6 12.19 Northeast, South
1910 February 16–18 11.34 Ohio Valley
1913 November 7–11 16.09 Ohio Valley
1915 March 2–8 17.67 Northern Rockies and Plains, South
1918 December 21–26 10.61 South
1929 December 16–21 10.62 Upper Midwest
1930 December 13–18 13.97 Southeast
1933 April 18–22 12.69 Northern Rockies and Plains
1936 February 6–8 11.26 Southeast
1947 January 27–31 10.18 Upper Midwest
1947 February 27 – March 4 10.63 Northeast
1949 January 1–6 15.79 Northern Rockies and Plains
1951 March 9–17 12.97 Upper Midwest
1955 April 3–6 16.93 Northern Rockies and Plains
1956 January 31 – February 6 13.78 South
1962 February 28 – March 7 11.79 Southeast
1962 March 5–9 12.66 Southeast
1966 January 27–31 12.28 Northeast
1969 December 25–29 10.14 Northeast
1971 February 26 – March 6 10.18 Northeast
1973 February 9–11 12.52 Southeast
1978 December 28, 1978 – January 3, 1979 10.08 Upper Midwest
1979 January 13–14 14.42 Ohio Valley
1979 February 17–20 15.01 Southeast
1979 November 17–22 10.81 Northern Rockies and Plains
1980 February 5–10 10.55 South
1980 February 28 – March 3 15.14 Southeast
1983 February 10–13 14.78 Southeast
1985 March 1–5 15.18 Upper Midwest, Northern Rockies and Plains
1987 January 21–24 13.16 Southeast
1987 April 2–6 11.21 Ohio Valley
1999 January 2–4 15.30 Upper Midwest, Ohio Valley
2003 February 14–19 14.67 Northeast
2004 December 21–24 11.31 Ohio Valley
2005 January 20–23 10.34 Northeast
2006 March 19–22 14.22 Northern Rockies and Plains
2009 March 27–30 14.95 South
2009 December 16–20 15.71 Southeast
2010 February 5–6 10.15 Southeast
2010 February 8–13 12.75 South
2010 February 10–13 10.07 South
2010 February 25–27 15.85 Northeast
2011 February 9–11 11.80 South
2014 February 11–24 10.66 Southeast
2017 March 11–15 10.66 Northeast
2018 April 13–15 15.7 Upper Midwest
2022 December 13-20 10.35 Upper Midwest
2022 December 21–26 11.49 Upper Midwest

Listed by month

See also

References

  1. ^ a b "Regional Snowfall Index (RSI)". NOAA: National Centers for Environmental Information. Retrieved December 26, 2020.
  2. ^ a b "Regional Snowfall Index and Societal Impacts". Retrieved December 26, 2020.
  3. ^ "NOAA Product Highlight: Regional Snowfall Index". Archived from the original on November 29, 2014. Retrieved December 26, 2020.
  4. ^ a b Squires, Michael; Lawrinmore, Jay; Heim, Richard; Robinson, David; Gerbush, Mathieu; Estilow, Thomas. "The Regional Snowfall Index" (PDF). American Meteorological Society. Retrieved December 26, 2020.
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