Moisture Update - April 7, 2024

Maps 1, 2, & 3: Since March 24, 2024, most of the Southern Region along with western portions of the province, from the USA border north to Grande Cache, have continued to receive meaningful moisture. Most agricultural land south of the TransCanada Highway received over 15 mm, grading to over 25 mm in and around Lethbridge (Map 1). This is significant for this time of year and marks a good start to April, historically the start of the wet season in this part of the province (Map 2). In contrast, throughout much of the North East and Peace Regions, conditions have remained relatively dry, with less than 3 mm being recorded across large areas (Map 1). These lands are exceptionally dry following a warm, dry fall and winter. They are currently in need of moisture, although unfortunately the wet season in this area of the province typically does not begin until late May (Maps 2 & 3).

Many of the mountain snowpacks surveyed still appear to be below recorded averages, based on the last survey issued in early March. However, since the start of 2024, conditions have generally improved, and five high-elevation stations in southwestern Alberta have recorded over 300 mm of precipitation, since January 1, 2024.  The highest amount was recorded at the Spionkop Creek Station at 405 mm, followed by the Gardiner Head Waters Station at 385 mm.  In the 14-days since March 24, both of these sites have recorded more than 50 mm of precipitation. 

For perspective, the Gardiner Creek Snow Survey, measured in mid-February, reported 501 mm of snow-water equivalent, which was 100 mm below average at that time. Between 1983-2024, the lowest measured value for that time of year occurred in 2001 at 283 mm, with the highest in 1991 at 1008 mm.  For those interested in the surface water supplies, please visit Alberta River Basins for the latest information.

Maps 4 & 5: Recent precipitation trends have ranged from near to above normal through much of the Southern and Central Regions, and hopefully this continues into the foreseeable future (Map 4).  Elsewhere, most of the North East and Peace Regions have remained in the drying trend that has persisted since at least September 2023. 

Precipitation over the past 30-days ranges from well over 40 mm in parts of the Southern Region, to less than 5 mm across large areas in the North East and Peace Regions (Map 5).

Map 3 & Graph 1: While we have seen a marked turnaround in moisture conditions across the southern parts of the province, the north remains very dry.  The lack of winter precipitation, along with warm spells and episodes of melting, left many areas virtually snow free for most of March. This is particularly concerning for the Peace Region and Alberta’s northern forested areas, as historically the winter period (October to March) accounts for over 30% of the annual precipitation. Most of this moisture is stored in the snowpack and then released in April as melting gets underway.  This provides an abundance of moisture that tends to replenish surface water supplies and allows plant growth to get a good start once plants break dormancy.  

Across the north, historically March and April are amongst the driest months of the year and it’s usually not until mid-May that the wet season begins (Map 3). So even with a return to near normal precipitation over the next 5 weeks, it could still remain relatively dry.  If you superimpose a rolling 7-day, 30-year average precipitation chart for Lethbridge (blue bars) over Manning (black bars), it’s clear that, on average, the south tends to get moisture early, mid-March, with an abrupt end in July. This is why early seeding and irrigation are so important here.  In contrast the Peace Region stays dry until mid-May, averaging less than 4 mm of precipitation per week from March 1 to the end of April, highlighting the importance of healthy snow packs. The wet season finally gets underway late May, peaks from mid-June through to the end of July, and generally persists until early September.