Ministry of FLNRO

Snow Survey and Water Supply Bulletin - June 15th, 2015

The June 15th snow survey is now complete. Data from 2 snow courses and 49 snow pillows around the province and climate data from Environment Canada have been used to form the basis for the following report.  This is the final Snow Survey report for the season.

Click here for the Snow Survey and Water Supply Bulletin as a PDF file.
Click here for the complete June 15, 2015 Snow Survey Data.

Weather
June weather has continued to be warm across the province. This included a prolonged hot spell through the second week of the month which saw temperature records being broken in many areas of the province. Episodes of low pressure brought some wetter periods in the first half of June, particularly in the Kootenay, Prince George area and north-east. Coastal areas in the south-west and western parts of the province have seen limited precipitation in June.

Snow Pack
Rapid melt of the province’s snow pack in May has left very little snow across the province as of June 15th. Snow basin indices are extremely low for June 15th (Table 1), and this reflects the rapid melt of the snow pack earlier this season. Snow basin indices range from 0% to 20% of normal, with a provincial average of snow observations of 5% of normal.

Most snow observation sites (automated snow pillows and manual snow surveys) are located in sub-alpine or forested areas at mid-elevation, and the lack of snow reported on June 15th reflects snow conditions in similar terrain across the province. Remaining snow is limited to the alpine terrain of the province’s mountainous regions.

Table 1 - BC Snow Basin Indices – June 15, 2015


Basin

% of Normal

Basin

% of Normal

Upper Fraser West

NO DATA*

Boundary

3

Upper Fraser East

10

Similkameen

0!

Nechako

17

South Coast

0!

Middle Fraser

8

Vancouver Island

0!

Lower Fraser

0!

Central Coast

0!

North Thompson

20

Skagit

NO DATA*

South Thompson

7

Peace

0!

Upper Columbia

5

Skeena-Nass

0!

West Kootenay

11

Stikine

0!

East Kootenay

1

Liard

NO DATA*

Okanagan

0!

Northwest

NO DATA*

*    Data is not available either because there were no scheduled snow surveys or no snow surveys were completed.
!    Zero values are the result of no snow being observed at snow basin index survey locations. Snow may still be present at higher, unsampled, locations

Streamflow Runoff

With earlier than normal melt of the snow pack across the province, most rivers are now on the receding end of the snow melt freshet. With waning influence of snow melt on river flow, many rivers in the province have declined to below normal flows for this time of year. In lower elevation areas, and areas that had limited initial snow packs this season, river levels have dropped to extremely low levels for mid-June. Flows are at or near minimum levels for this time of year in most rivers on Vancouver Island, Haida Gwaii and South Coast. Current flows in these regions are below levels normally observed in late-summer.

Well below normal flows are also present through the South Interior, Central Interior, Kootenay, and areas of the Peace. Current flows in these regions are at levels more typically observed in mid-July to August.

The Fraser River at Hope (08MF005) has seen 65% of the forecasted April to September runoff volume passed as of June 18th, and flows have dropped to 5200 m3/s from a peak of 7950 m3/s earlier this month. Flows are at approximately 75% of normal levels for this time of year. There is now a limited supply of snow in the watershed that flood risk has now subsided.

Elsewhere in the province, current flows are variable, with most rivers at near-normal levels, with localized areas of above-normal (particularly around the Nechako River) and below-normal flows.  A flood warning remains for the Nechako River with current flows at Vanderhoof (08JC001) of approximately 651 m3/s (5.29m) and at Isle Pierre (08JC002) of 1030 m3/s (4.97m).

Outlook

Short-term weather forecasts indicate the potential for rainfall over the next week, with wet conditions across central British Columbia, and moderate rainfall elsewhere. Long-term weather forecasts from Environment Canada continue to indicate a high likelihood of above-normal temperatures across the province through the summer. Warm sea surface temperature anomalies in the North Pacific Ocean, and building El Niño conditions along the equatorial Pacific reinforce the high likelihood of a warmer than normal summer. Seasonal precipitation forecasts indicate a modest likelihood of below normal precipitation in south-east BC. Elsewhere in the province, normal to below normal precipitation is forecast to be more likely than above normal conditions.

With the emergence of low flow patterns already this season and the forecast for a warmer than normal summer, there is a high risk of extreme low flows this summer. Areas where extreme low flows are expected include southern BC, Vancouver Island, and Haida Gwaii and potentially in other regions including the Peace and South Interior. Summer rainfall can contribute significantly to streamflow and will be a determinant in the extent of low flows later in the summer. Given the likelihood for normal or below normal precipitation, there is an increased risk that low flow conditions will continue to deteriorate across the province; wetter than normal conditions through the summer may alleviate some of this risk.

The River Forecast Centre will continue to monitor weather and streamflow across the province and will provide Water Supply Bulletins and low streamflow advisories as needed. The Flood Watch currently posted for the Nechako River will be revised as conditions warrant.

BC River Forecast Centre
June 18, 2015