A spell of very cold and rainy weather is set to hit South Africa’s Western, Northern, and Eastern Cape regions on Thursday, 10 May 2023, extending into the weekend.
Weather forecast for Thursday, 10 May 2023 – Heavy rain expected in these provinces
According to the South African Weather Service (SAWS), this weather pattern will be caused by the arrival of a cold front over the southwestern part of the Western Cape on Thursday morning.
The arrival of the cold front will lead to a significant drop in daytime temperatures across the southern half of the country.
This will be accompanied by a range of wintry weather, including widespread significant rainfall and snowfalls over mountainous terrain. Additionally, marine gales and very rough seas are expected over the southern oceanic areas.
Upper-air troughs and closely related cut-off lows are common in the weather patterns of southern Africa and are often associated with prolonged episodes of rainfall, which can be extreme.
It is noteworthy that the extreme rainfall and flooding that affected KwaZulu-Natal (KZN) during April and May 2022 were caused by cut-off low weather systems on both occasions.
This week’s weather pattern will be characterised by a well-developed upper-air trough, which will start moving towards the Western and Northern Cape from Thursday onwards.
It will subsequently cut off and establish a cold core, characteristic of cut-off upper-air systems. Additionally, a strong southern Atlantic high-pressure system is expected to extend a ridge eastward in the wake of the cold front.
This will introduce pronounced and sustained onshore flow along the southern coastline of the Western Cape, as well as the Eastern Cape, during the weekend.
Snowfall in Western Cape is POSSIBLE this weekend
Moreover, the presence of coastal mountain ranges, such as the Outeniqua and Swartberg, will enhance the vertical motion of air, increasing the likelihood of heavy orographically-induced rainfall.
This combination of surface and upper-air systems is expected to raise the likelihood of significant, widespread, and heavy rainfall, especially over the coastal mountain regions, leading to localised flooding.
Day-time temperatures for this week are expected to drop significantly from Friday, 12 May 2023, into Saturday, 13 May 2023, with maximum temperatures below 10°C in some places.
Light snowfall is possible over the southwestern mountains of the Western Cape as well as the southern high ground of the Northern Cape on Friday afternoon into Saturday.
The sea state will also be affected, with wave heights of 4.0 to 5.0m between Alexander Bay and Plettenberg Bay from Friday into Saturday.
Strong to near gale force south-easterly winds are expected north of Cape Point on Friday while spreading along the south coast on Saturday. These strong winds, accompanied by significant wave heights, will result in very rough and choppy sea conditions.
Cloudy and cold to very cold weather will dominate the Northern and Western Cape from Friday onwards, spreading to include most of the Eastern Cape during the weekend.
Widespread rain and showers will accompany this system, with the likelihood of heavy rain and localised flooding being of particular concern for the southern and south-eastern coastline and adjacent interior.
Farmers of small stock are advised to move animals to dry shelters at lower elevations.
Additionally, only experienced and well-prepared hikers and climbers should venture into the mountains and hiking trails of the Western and Eastern Cape this weekend.
The risk of hypothermia in mountainous terrain, especially if lost, injured, or ill-prepared, could prove to be life-threatening.