Extremely high snow pack (>130 per cent) is present in the Upper Fraser East and the Cariboo Mountains (Quesnel River). Several snow measurement locations recorded all-time record high Snow Water Equivalent (SWE) values for May 1. These include:
- 1A17P (Revolution Creek): 1378 mm with 31 years of record (Upper Fraser – East)
- 1C13A (Horsefly Mountain): 712 mm with 48 years of record (Middle Fraser/Quesnel)
- 1C41P (Yanks Peak East): 1274 mm with 23 years of record (Middle Fraser/Quesnel)
- 1E14P (Cook Creek): 650 mm with 11 years of record (North Thompson)
- 2B08P (St. Leon Creek): 1595mm with 26 years of record (West Kootenay) High snow packs (>120 per cent) are present in the Central Coast and South Thompson.
Moderately high snow packs (110-120%) are also present in the North Thompson, Upper Columbia, West Kootenay, East Kootenay, Okanagan, Boundary, Similkameen, Skagit, Peace and Northwest.
The overall snow basin index for the entire Fraser River basin (e.g. upstream of the Lower Mainland) is 110 per cent. During freshet, most of the flow (roughly two-thirds) in the Fraser River originates from the Upper Fraser East, North Thompson, South Thompson and Cariboo Mountains. Snow pack in these areas is very high (130 per cent of normal).
The snow pack in unregulated watersheds of the Fraser River upstream of Hope (e.g., excluding the Nechako and Bridge systems, which are regulated by dams) are currently among the highest on record.
For perspective, recent years with high May 1 snow basin indices for unregulated watersheds of the Fraser River upstream of Hope include 2018 (119 per cent), 2012 (125 per cent), 2007 (127 per cent), and 1999 (126 per cent).
Cool weather in the first half of April led to a delay in the onset of low elevation snowmelt. A moderate warm spell with slightly above normal temperatures resulted in rapid thaw of frozen rivers and quick melt of low elevation snow.
Low-elevation rivers in the Chilcotin Plateau, the Cariboo Region near Williams Lake, rivers surrounding Prince George, and the Bonaparte River at Cache Creek experienced flood levels in late April. Extreme cold weather over the winter and early-spring may have also contributed to increased ice-jamming and rapid runoff during the warming in mid-April.
Many rivers in the province are experiencing above-normal flows for early-May. This reflects early melt of low-to-mid elevation snow, with flows two to three weeks ahead of normal in some areas. In watersheds with an increased proportion of high elevation, mountainous terrain, streamflow is more typical for this time of year and flows are expected to increase as high elevation melt proceeds.