30 to 40% of normal Snowpack…Ouch!

Subject: Snow Survey and Water Supply Bulletin – February 1, 2014
Importance: High

The February 1st snow survey is now complete. Data from 119 snow courses and 51 snow pillows around the province and climate data from Environment Canada form the basis for the following report.

The full version of the bulletin including text, data, graphs and basin index map can be viewed at the  River Forecast Centre web site: http://bcrfc.env.gov.bc.ca/bulletins/watersupply/current.htm

Weather

January weather was dominated by persistent high pressure systems which led to dry conditions for most of the month. One period of unsettled weather occurred earlier in the month, and led to some additional snow accumulation across the province. January precipitation was well below average across the province. Particularly dry regions, with January precipitation amounts in the 30-60% of normal range, included the South Coast, Vancouver Island, North Coast, South Interior, and Central Interior. For most of the south half of the province, precipitation has been below normal since October.

Temperatures in January were above normal across the province. Temperatures on Vancouver Island and the South Coast were 0-2˚C above normal, 1-4˚C above normal in the North Coast, Okanagan, South Interior, Kootenay, Columbia and Thompson regions, and 3-8˚C above normal in the Chilcotin, Cariboo, Prince George, Skeena, Peace and Northern BC.

Snowpack

Dry conditions through January led to a decline in snow basin indices in most regions of the province. Snow basin indices range from a low of 28% of normal on Vancouver Island, to a high of 174% in the Liard (Table 1). Most regions of the province have normal to slightly below normal snow pack (80-100%; See Figure 1). Note the River Forecast Centre is now using the 1981-2010 normal period for snow water equivalent normal values compared to the previously used 1971 – 2000.  Normal values for this period for individual snow observation locations can be found in Appendix 2.

Table 1 – BC Snow Basin Indices – February 1, 2014

Basin

% of Normal

Basin

% of Normal

Upper Fraser

144

Okanagan-Kettle

88

Nechako

80

Similkameen

82

Middle Fraser

98

South Coast

43

Lower Fraser

49

Vancouver Island

28

North Thompson

90

Central Coast

91

South Thompson

96

Skagit

34

Upper Columbia

92

Peace

104

Lower Columbia

92

Skeena-Nass

89

East Kootenay

93

Stikine

93

West Kootenay

83

Northeast-Liard

174

 The north-east corner of the province have above average snow basin indices, with very heavy snow packs (>140%) in the Liard and Upper Fraser basins. Several individual surveys in the Liard and Upper Fraser have record, or near record values for the February 1st survey period.  The snow basin index for the Upper Fraser is similar to the record conditions observed in 2012.

Very low snow packs (25-50% of normal) persist in the south-west part of the province, including Vancouver Island, South Coast, Lower Fraser and Skagit basins. The last time that similar low snow pack conditions were observed in these regions was in 2005, and in the past 40 years lower snow packs than present have been observed approximately once every 10-15 years.

Streamflow

Runoff in many watersheds in the BC Interior has been near normal to above normal through the current water year (October 1st, 2013 to January 31st, 2014).This is likely the result of warmer temperatures and an increased portion of precipitation falling as rain rather than snow. Stream flow in Coastal watersheds has typically been below normal through this water year, as a result of dry seasonal conditions.

 Outlook

By early February, generally about two-thirds of the annual BC snowpack has accumulated. Conditions in the Upper Fraser and Liard (>130% of normal) indicate the potential for increased seasonal flood risk.

In the south-west (Vancouver Island, South Coast, Lower Fraser, Skagit) the low snow packs indicate that we can expect below normal seasonal runoff during the spring melt. Given the time of year, it will require significant wet weather over the next 2-3 months to recover the snow pack to normal levels. While lower spring runoff can be expected, spring and summer weather conditions will be the key factor in determining whether or not drought and low flows will occur this summer. These regions will continue to be monitored closely for potential impacts of the low snow pack on stream flows.

Seasonal volume runoff forecasts (in Appendix below) have higher than normal runoff forecasted in the Upper Fraser and Middle Fraser basins, near normal runoff forecasted in the Thompson, Okanagan, Similkameen and Skeena basins, and below normal runoff forecasted in the Nicola basin.

The winter 2013-2014 has been characterized by neutral ENSO conditions. The Climate Prediction Centre at the U.S. National Weather Service/NOAA has forecast continued neutral conditions through spring and summer 2014. In general, neutral ENSO conditions do not indicate an increased likelihood of either wet or dry seasonal weather, however local weather conditions may vary from the long-term average through the province.

Seasonal forecasts from Environment Canada indicate most of the province, except for south-west regions, has an increased likelihood of cooler than average conditions for the period February to April 2014. Forecasts for seasonal precipitation do not indicate an increased likelihood for any particular trend.

The River Forecast Centre will continue to monitor snow pack conditions and will provide an updated seasonal water supply and flood risk assessment in the March 2014 Snow Bulletin, scheduled for release on March 10, 2014.

Produced by: BC River Forecast Centre

February 7, 2014

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