Date: 19 June 2019
Period: 18 June until 21 June 2019
A high-pressure cell has been dominating the interior slightly shifting back and forth, up and down, and all the while capping any development of thunderstorms that may have occurred. At night the high-pressure cell allows for clear skies leading to greater radiative cooling. This combined with cooler air masses has allowed for night-time temperature to drop below freezing hence we've had bitterly cold mornings and frost over most of the interior where the high has been dominating.
The high pressure will continue this dance today (Tuesday), allowing for a clear sky day followed by a bitterly cold morning once again tomorrow (Wednesday). For the rest of today, the western coastline and its adjacent interior will be affected by northerly winds flowing down the western escarpment and heating up the surrounding areas as berg winds. Temperatures are expected to average 31ºC for most of the towns from Vredendal to Alexandra Bay, with 25ºC expected for Cape Town.
On Wednesday, moderate northerly winds will dominate the interior during the day due to the high pressure cell receding towards the Indian Ocean. But before it leaves permanently, it pushes moisture from the eastern part of the Eastern Cape to KwaZulu-Natal's coast and adjacent interior including the northern parts of lowveld in the form of fog and drizzle. Frost and cool air masses also migrate towards the north-eastern part of the country.
On Thursday, it'll be partly cloudy along the west and south coastlines due to an onshore flow ahead of an approaching cold front. Towns right along the coast like Cape Agulhas and Cape Town may see light showers on Thursday with strong winds at times. Winds of up to 40km/hr and from the north to northwest are expected over the Western Cape, Northern Cape and western parts of the Eastern
Cape. Later on towards the evening, over the north-eastern parts, cloudy conditions with drizzle will spread from east to west covering Limpopo, Mpumalanga, Gauteng and Northern KwaZulu-Natal continuing into Friday morning.
Morning fog patches on Friday will clear up quickly over north-eastern parts of the country as a well-developed cold front grips the western coastline all the way to Namibia. These front spreads its influence to the interior where it changes winds to north-west from early on in the day, around midday winds over the Cape Province will reach 60km/hr followed by cloudy conditions and showers in places far from the coast. Most of the rain will be confined to the coastal areas as that's where it'll start and continue raining as the cold front spreads its influence over the interior. Later on Friday the winds change to westerly or south-westerly with cold temperatures along the coast and light snow over high peaks such as Sutherland.
Over the weekend, as the front progresses east, so do the showers, migrating towards the Eastern Cape where along the high peaks close to Graaff-Reinet light snowfall is possible with the showers confined to the coast and adjacent coastline. Bitterly cold temperatures are expected for the Cape provinces this weekend including Free State, southern North West, and southern KwaZulu-Natal.
Storms containing large hail: (any mention of thunderstorms in the forecast automatically presumes a very low chance of large hailstorms). Not expected.
Intense lightning: (any mention of thunderstorms in the forecast automatically presumes a low chance of intense lightning). Not expected.
Flash flooding: (any mention of thunderstorms in the forecast automatically presumes a very low chance of flash flooding). Medium to high chance near the mountains in the SW Cape on Friday, with a medium chance away from the mountains.
Low to medium chance along the Cape S coast on Saturday and Sunday morning.
Fire risk: Low risk over western areas today (Tuesday).
Other: Strong winds at the end of the working week in western and southern areas along with the chance of snow falls. A sharp frost and very cold conditions can be expected over the weekend.
Very high 90-100% chance.
High 80% chance.
Medium 60% chance.
Low 40% chance.
Very low 20% chance.
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