During the last 24 hours the GFS model runs (up to 12Z on Sun 21st) have shown several interesting scenarios, though there is still little consistency at longer durations. Very heavy rainfall (> 50mm/day) is possible over the central and eastern parts of South Africa during the cutoff-low (Sat 27th), but the timing, location and amount are impossible to specify this far in advance.
The passage of the detached cold-core upper trough over the western interior of South Africa on Thurs 25th, has the potential for further freakish outcomes, with the possibility of (very light) snow as far north as Central Namibia (near Windhoek)! This is indicated by both today’s 06Z and 12Z GFS runs, though the amount of moisure in circulation will be limited, and only traces of precipitation (if any) are possible.
Subsequent model runs are likely to flip-flop further, but eventually the outcome at longer durations should become clearer. At that stage I will post further charts covering the development of the cutoff-low, and the potential for snow over the eastern half of South Africa during Fri 26th and Sat 27th.