Snow Survey and Water Supply Bulletin – January 1st, 2017

   Table 1 - BC Snow Basin Indices – January 1, 2017

Basin	% of Normal	Basin	% of Normal
Upper Fraser West	59*	Boundary	73
Upper Fraser East	62	Similkameen	100*
Nechako	90	South Coast	114
Middle Fraser	82	Vancouver Island	98
Lower Fraser	111	Central Coast	87*
North Thompson	87	Skagit	110*
South Thompson	100	Peace	59
Upper Columbia	88	Skeena-Nass	65
West Kootenay	80	Stikine	54*
East Kootenay	87	Liard	49*
Okanagan	79	Northwest	NO DATA

The January 1^st snow survey is now complete. Data from 77 snow courses and 69 automated snow weather stations around the province, collected by the Ministry of Environment Snow Survey Program and partners, and climate data from Environment and Climate Change Canada have been used to form the basis of the following report¹.

Full details on the snow bulletin, including the snow basin index map and snow survey data can be found at: http://bcrfc.env.gov.bc.ca/bulletins/watersupply/current.htm

Weather

Fall and early-winter weather had been variable across the province. October featured near-normal temperatures across most of the province, with wet conditions through southern BC and the North-East, and drier than normal conditions through the Central and North Coast.

November was extremely warm across the province, with most areas experiencing monthly average temperatures that were 2-5˚C above normal. Weather patterns were dominated by Pacific storm cycles. November was generally wetter than normal across the province, and much wetter than normal in south-west BC. Numerous significant storm events in November led to flooding on Vancouver Island and the South and Central Coast.

Weather patterns flipped in December, ushering in the dominance of Arctic air across British Columbia. Monthly temperatures were typically 2-5˚C below normal across the province. Precipitation through December was generally below normal to near normal across the province, with some areas of the South Interior experiencing above-normal precipitation. While precipitation amounts were not exceptional, cold temperatures led to much higher than normal (typically 130-300% of normal) snowfall throughout December for low elevation areas of south-west BC.

Two key weather factors have been driving the seasonal snowpack development this year. First is the extremely warm November period across the province. This led to a delay in the early season accumulation of snow, and in some areas led to melting of the early season snow that had fallen in October. During November, river runoff from melting snow and moderate to heavy rainfall, led to extremely high seasonal flows for most river systems in the BC Interior. The second key weather driver has been the dominance of Arctic air across the province through December. This has led to dry conditions, particularly across northern BC, and cold conditions across the province. Colder than normal temperatures in south-west BC has led to much greater snow accumulations at low elevation, while the impact on higher elevation snowpack has been modest. Snow at low elevation has been much higher than normal through December, with many areas receiving twice as much snow as normal, or more.

Table 1 - BC Snow Basin Indices – January 1, 2017

Basin	% of Normal	Basin	% of Normal
Upper Fraser West	59*	Boundary	73
Upper Fraser East	62	Similkameen	100*
Nechako	90	South Coast	114
Middle Fraser	82	Vancouver Island	98
Lower Fraser	111	Central Coast	87*
North Thompson	87	Skagit	110*
South Thompson	100	Peace	59
Upper Columbia	88	Skeena-Nass	65
West Kootenay	80	Stikine	54*
East Kootenay	87	Liard	49*
Okanagan	79	Northwest	NO DATA

*Note January 1^st snow basin index values are based on limited observation points

January’s snow survey schedule features fewer individual snow survey measurements than occur in later survey periods in the year. Some January 1^st snow basin indices are therefore based on a very limited number of surveys (e.g. 1-2 surveys within the snow basin) (Table 1) making the data interpretation less robust compared to survey periods later in the season. All available January 1^st snow measurements are provided at the end of this report.

Outlook

Weak La Niña conditions in the equatorial Pacific Ocean appear to have peaked. The Climate Prediction Centre (CPC) at the U.S. National Weather Service/NOAA is forecasting La Niña conditions to weaken through the remainder of the winter, and is forecasting a high likelihood of neutral ENSO conditions by the January to March period. Typically, La Niña is linked to cooler and wetter winters across British Columbia.  Snowpacks tend to be higher than normal; however, there has been a large range of variability in snowpack during La Niña winters in the past. Given the weak nature of the current La Niña cycle, there is greater uncertainty regarding how it will influence this year’s conditions.

Seasonal forecasts from Environment and Climate Change Canada are indicating an increased likelihood of below-normal temperatures across northern and western British Columbia over the January to March period. Short-to-medium term forecasts are suggesting colder temperatures through the middle of January, and an increased likelihood of warmer conditions into the second half of the month.

By early January, nearly half of the annual BC snowpack has typically accumulated. At this early stage in the season, there is limited indication that any regions of the province are developing increased seasonal flood risk. Currently observed low snow pack in some regions of the province, particularly the northern third of the province, is an early indication of the potential for lower than normal stream flow in the spring and summer this year. However, with three or more months left of snow accumulation, these outlooks could change significantly.

The River Forecast Centre will continue to monitor snow pack conditions and will provide an updated seasonal flood risk forecast in the February 1^st 2017 bulletin, which is scheduled for release on February 7^th.

BC River Forecast Centre
January 9, 2017

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