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Northern Hemisphere 2019-2020 Winter Snow Cover

Ross Brown (ECCC), Patricia de Rosnay (ECMWF), David Robinson (Rutgers), and Kari Luojus (FMI)
16 February 2020, updated 3 April 2020

Northern Hemisphere Snow Cover, August 2019 - February 2020

The 2019-2020 Northern Hemisphere (NH) snow season through January is notable for a marked lack of winter snow cover over Europe (Figure 1) driven by record-breaking warm temperatures and below-average precipitation for most of Europe. As of 4 February 2020 the snow line over Europe is ~20° of latitude further north than normal, with major negative impacts on the alpine ski industry. The 2019-2020 snow season in North America was characterized by early winter snowstorms at a number of cities, and above-average winter snow accumulations, most notably over eastern Canada and Newfoundland.

Figure 1: Snow cover anomaly for January 2020. (Rutgers University Global Snow Lab).

Snow cover duration: Anomalies of August-January snow cover duration (SCD) from the CMC operational snow depth analysis (from surface observations) and the IMS24 daily snow cover analysis (from mainly satellite data) are in good agreement (Figure 2). The main features are: (1) anomalously low snow cover over most of Europe, with anomalies exceeding -40 days over the Baltic States and Northwest Russia, and (2) above-average snow cover over most of the mid-latitudes of North America (NA). The low snow cover in Europe is a consequence of record warm winter temperature over the region and lower than average precipitation (see news items below) that has caused havoc with the ski industry. Early winter snowstorms were a feature of the 2019-2020 snow season across the Midwestern US and Canada.

Figure 2: Difference in August-January snow cover duration (days) between 2019-2020 season and the 1998-2017 average for the CMC operational snow depth analysis (left) and the NOAA IMS24 daily snow cover analysis (right).

Winter snow accumulation: Anomalies of January mean snow depth from the CMC operational analysis are more or less consistent with the snow cover anomalies indicating large negative anomalies over most of Europe, with above average snow depths over most of NA mid-latitudes (Figure 3). The daily snow depth anomaly plot for 4 February 2020 (Figure 4) shows most of Europe snow-free, with the snowline about 20° of latitude further north than normal. Winter snow depths are above average over many regions of NA, in particular, northern latitudes and eastern Canada where a record-breaking late-January snowstorm generated drifts of 1-2 m in St-John’s. Figure 5 shows the January 2020 snow water equivalent (SWE) anomaly from GlobSnow.

Figure 3: Difference (%) between January 2020 mean snow depth and the 1999-2018 average for the CMC operational snow depth analysis.

Figure 4: Snow depth departures (cm) from CMC operational daily snow depth analysis for 4 February 2020 versus the average value over snow seasons 1998/99 through 2011/12.

Figure 5: January 2020 snow water equivalent (SWE) anomaly relative to the 1981-2010 mean from GlobSnow.

Hemispheric-averaged anomalies: Figure 6 shows January snow cover anomalies for every year from 1967 through 2020. The GCW NH snow anomaly tracking products from CMC and GlobSnow (Figures 7 and 8) indicate normal to slightly below-normal snow cover extent to date, but with above-average SWE. The above-average accumulations are most noticeable over higher latitudes (Figures 3 and 4).

Figure 6: January Northern Hemisphere snow cover anomalies, 1967-2020. (Rutgers University Global Snow Lab)

Figure 7: 2019-2020 snow season history as of 4 February 2020, for Northern Hemisphere land area snow cover extent (top) and estimated snow water equivalent (bottom) compared to ±1 standard deviations about the 1998/99 to 2011/12 average from the CMC operational snow analysis.

Figure 8: 2019-2020 snow season history as of 4 February 2020, for Northern Hemisphere land area (excluding mountains) snow water equivalent compared to ±1 standard deviations about the 1982 to 2012 average, from the GlobSnow Product.

Other

[3 April 2020] There have been major regional differences in the amount of snowfall in Norway this winter. While parts of southern Norway are welcoming a greener spring, many places in Norway are still covered in large amounts of snow. Read more from the Norwegian Meteorological Institute (METNO) Cryo Team.

Figure 9: Snow cover map from April 1 2020. This map is based on satellite imagery from several days to be able to fill inn for areas of missing data due to cloud cover. From METNO.

As The S2S4E Project reports, there was above-normal precipitation in Scandinavia from January through March. There is now more snow in the mountainous areas, so snowmelt will result in high water inflow to hydropower reservoirs in May, June, and July.

Snow in the News