South Africans can expect a cold snap to affect most parts of the country from the middle of this week onwards. A steep upper-air trough, having the potential to cut off and further intensify, will result in significantly cooler weather over most parts of the country on Wednesday into Thursday, with the expectation of snowfalls on some southern mountains.
Maximum temperatures of the order of 16 to 19 °C will affect the southern parts of the Western Cape from tomorrow (Tuesday), 14 November 2017, with cold weather spreading further eastwards and northwards on Wednesday and Thursday. Cold weather will invade the Eastern Cape, southern KwaZulu-Natal, southern Free State and the Northern Cape on Wednesday, spreading to reach the remainder of KwaZulu-Natal, the Free State, Gauteng and Mpumalanga on Thursday, accompanied by maximum temperatures in the mid-teens. However, very cold weather, characterized by single digit maximum temperatures (+9 °C or less), will dominate high-lying areas of the Eastern Cape and south-western KwaZulu-Natal on Thursday.
Small stock farmers are strongly advised to take preemptive measures at an early stage, ahead of the onset of the inclement weather, in order to protect their livestock during this unseasonal cold snap. Figure 1 indicates predicted maximum temperatures for Thursday, 16 November 2017, based on the ECMWF model.
Significantly cooler weather in the upper-air will result in light snowfall over the high ground of the Western Cape as well as the western high ground of the Eastern Cape from Wednesday morning (15 November 2017) onwards. Snow is expected to subsequently spread eastwards to include the eastern parts of the Eastern Cape by Wednesday afternoon, where it will become heavy and disruptive (with respect to traffic and infrastructure) over the north-eastern mountains of the Eastern Cape (Rhodes, Barkly East) and Lesotho. Snowfalls of this nature typically lead to the closing of mountain passes, resulting in associated disruption to traffic flow. Further snowfalls, of a light to moderate nature, are expected to spread to the south-western and western high ground of KwaZulu-Natal as well as the south-eastern and eastern extremities of the Free State on Thursday, 16 November 2017.
Widespread rainfall can also be expected over much of the southern and eastern parts of South Africa. A strong ridging high pressure system will start to move in along the southern parts of the Western Cape on Tuesday, 14 November 2017, accompanied by onshore flow along the coast and adjacent interior regions, resulting in heavy rainfall (in excess of 50 mm in places in the Eden Districts) spreading eastwards to parts of the Eastern Cape, KwaZulu-Natal and eastern parts of Mpumalanga on Wednesday, 15 November 2017. Although rainfall is expected across most parts of the country on Wednesday, the heaviest rainfall is likely to be restricted to the aforementioned provinces. Instances of flooding can also be expected during this period.
The intensity of rainfall is expected ease off from the west on Thursday, 16 November 2017, but it will persist over parts of Mpumalanga, KwaZulu-Natal, the eastern parts of the Free State and in the Eastern Cape. Moreover, it will remain cold and windy over much of the interior of South Africa on Thursday.
Life saving tips in heavy rainfall/flooding and severe cold events:
- If possible stay indoors and off the roads, avoid crossing rivers and swollen streams where water is above your ankles.
- If trapped within a vehicle by rising waters, abandon it immediately and seek higher ground.
- In buildings, move valuables to a safe place above the expected flood level. Switch off electricity at the supply point to the building.
- In rural areas, protect animals by moving them to shelter, away from rain, snow and potential flooding.
- Abandon your home immediately, should authorities recommend evacuation, before access is cut off by flood water.
- NEVER drive on a road covered by water. You do not know how deep it is or if the road has been washed away.
- If the vehicle stalls, leave it immediately and seek higher ground.
- Be especially cautious at night when flood dangers are difficult to identify.
The South African Weather Service will continue to monitor any further developments relating to this weather system and will issue subsequent updates as required.