Hail and Tornado Threat Thursday in SK.   Heavy weekend rain in AB, SK.

Thursday

Alberta

A weak low-pressure system is bringing scattered showers and a few isolated thunderstorms to central Alberta. This rain will move northeast throughout the day and into tonight. Most areas can expect around 5 to 15 mm of moisture, but heavier local amounts are possible where thunderstorms develop.

This afternoon, a  trough stretching into southern Saskatchewan may trigger more storm activity in central Alberta.  Quickly building clouds could lead to funnel cloud development – something to be aware of, if you’re working outdoors.

The rain and storm activity should taper off overnight.

Central and southern Alberta will not be impacted to such a great extent, with little to no rain expected.   Where it rains, it will be cool, with highs near 15 degrees.   In the south, where rain is not expected,  highs will reach the mid 20s.

Saskatchewan and Manitoba

A significant severe weather threat is shaping up, especially from around Yorkton, SK to Virden, MB. A weather system that moved out of Alberta overnight is expected to sit just southwest of Saskatoon by midday. Moisture is building in eastern Saskatchewan, leading to humid conditions with dew points in the mid to upper teens.

Stronger winds higher up in the atmosphere and unstable air will make conditions favorable for powerful storms later in the day. The setup could support large hail—potentially bigger than golf balls—damaging wind gusts over 100 km/h, and even a few tornadoes.

The greatest risk for tornado development will be near a warm front, likely affecting areas around Yorkton and Virden. Storms will likely begin forming in the late afternoon, but they may be fairly isolated.

Elsewhere, in southern and southeastern Manitoba, expect quiet weather, with highs in the mid 20s

Friday,  Saturday, and Sunday

Heavy Rain

A major rain event begins Friday and continues through the weekend in southern Alberta and Saskatchewan.  Some areas will get well over 100 mm over the three days, with even more to come next week.   With upslope enhancement, up to 200 mm of rain could fall by the end of the weekend in the Pincher Creek/Waterton area.  The map below shows expected rainfall accumulation to midnight Sunday night:

Beginning Friday, a low-pressure system from the Pacific is expected to move inland, aiming for southern Alberta. As it arrives, strong southeasterly winds will pull in moist air, setting the stage for heavy rainfall, especially in areas with upslope (easterly) wind flow, such as the foothills.

Widespread totals of 50 to 100 mm across southern Alberta and into the foothills are expected by the end of the weekend. The southwestern foothills, especially around Pincher Creek and Waterton, could see up to 200 mm, due to both terrain effects and thunderstorm activity.

In addition, strong northeasterly winds are expected to pick up on Saturday across southern Alberta. Environment Canada advises that, combined with saturated soils, these winds could lead to tree damage or uprooting, which may pose risks around shelter belts, fence lines, and power lines near fields or livestock areas.

Saskatchewan will also experience heavy rainfall over the weekend, with perhaps over 75 mm in the Rosetown area.  Elsewhere across southern Saskatchewan, 30-50 mm of rain is expected.  As the map above shows, rainfall amounts taper off drmatically north of Saskatoon.

And in Manitoba, 30-40 mm of rain is possible between the Saskatchewan boundary and Lake Winnipegosis.  The rest of Manitoba’s agricultural south will get much less rain, though every drop is beneficial.

The rain will be accompanied by cold weather.   Highs across the southern prairies are expected to reach the mid to high teens on Friday.   With the heavier rain Saturday and Sunday,  highs will be even lower, between high single digits and mid teens.

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