Statement from the SA Weather Service
Wednesday, 10 May 2017
Significant drop in temperature this weekend
Whilst much of the country has enjoyed mild, sunny autumn weather of late, this is set to change fairly dramatically over the majority of the country this weekend.
Of particular importance for the general public as well as the farming community is a significant drop in daytime temperatures over many provinces, combined with light snowfalls over the Drakensberg Mountains.
At the current time, a cold front is positioned a few hundred kilometres to the south-west of the Western Cape (see Figure 1 below), expected to arrive over the SA Cape Peninsula on Thursday, bringing some light rain and moderate cooling to the region. However, being mindful of the severe and ongoing water shortage in the Western Cape, this particular weather system is not expected to provide any relief, as rainfall is likely to be light and short-lived, favouring mainly the southern coastal regions. Note too, that snowfalls are not expected in the Western Cape from this particular weather system. Snowfalls are however expected to occur over many of the provinces over the eastern half of the country, as explained in more detail below.
By contrast, the Eastern Cape can expect a markedly different sequence of events as the cold front moves through on Friday. An upper-air trough, associated with noticeably colder, unstable air (at an altitude of about 6km above sea level) is expected to intensify over the Eastern Cape, shifting to the Lesotho section of the Drakensberg on Saturday, when further intensification of the system is expected. The middle layers of the atmosphere will moisten and become progressively colder, allowing snow to fall over higher elevations in the Eastern Cape, particularly in the Barkly East area. Whilst snowfall will, for the most part, be relatively light, there is still the likelihood of disruption and temporary closure of some mountain passes. Similarly, on Saturday further snowfalls can be expected in this region, spreading to include the extreme eastern Free State (bordering Lesotho) as well as the highlands of KwaZulu-Natal. Notably, van Reenen’s pass on the N3 highway may experience temporary closure due to snowfall on Saturday as well as Sunday. Such disruptions or interruptions in traffic flow are however not expected to be long-lasting.
As mentioned in the opening paragraph, a feature of this weather system which is arguably of greater concern, especially for farmers of small stock, is the dramatic drop in temperature, expected for many provinces. In particular, temperatures in the Eastern Cape are likely to drop by at least 15°C within 24 hours, in the period between Thursday and Friday. Whilst the interior of this province can expect balmy weather, in the mid to upper twenties, many parts will struggle to reach 10°C by the following day. This scenario, combined with showers and general windiness could well lead to stock losses if livestock are not led to shelter at lower elevations before the onset of the bitterly cold weather. Similarly, farmers in the eastern Free State, KwaZulu-Natal, Lesotho and the eastern Highveld of Mpumalanga are urged to take necessary steps on Thursday and Friday to ensure the safety and wellbeing of sheep, goats and cattle, ahead of the weekend.
Whilst the abovementioned provinces will bear the brunt of the inclement winter weather, there will also be significant cooling experienced across the Highveld by Saturday. Southern Gauteng and the eastern Highveld of Mpumalanga will be distinctly chilly, at about 12 to 16 C, whilst northern Gauteng and Pretoria will only be marginally warmer. Some showers or thundershowers are also a possibility over the Highveld at the weekend. At this stage, the SA Weather Service does not anticipate any snow for the Highveld, although a few light, brief flurries cannot be ruled out for the eastern highland areas of Mpumalanga, in the area of Dullstroom and the Roossenekal Pass. The Highveld on Sunday will be slightly warmer, after a chilly start but it will however remain a cold day.
The good news is that by Monday the 15th we can look forward to a general recovery of daytime temperatures across the entire country, when many regions will experience sunny, mild weather, although the Drakensberg, at higher elevations, will remain clear but cold.
The South African Weather Service will continue to monitor further developments during this period and will issue subsequent updates as required. Furthermore, the general public are urged to regularly follow weather forecasts on television and radio.
Image: Meteosat RGB satellite image at 13h00SAST Wednesday 10th May 2017, indicating the position of the upcoming cold front (bluish cloud band at lower left of image) approaching the country. © Eumetsat 2017.
