South Australian Forecast by Ben Matson (issued Wednesday May 7th)

Features of the Forecast (tl;dr)

• Fun clean surf on the Mid Thurs, easing Fri, becoming very small over the weekend
• Large, easing swell down south Thurs with rapidly improving conditions
• Decent waves with favourable AM winds down south Fri, Sat, Sun
• Small clean leftovers Mon/Tues
• Small new groundswell Wed (down south)
• Better groundswell Thurs (both coasts)
• Potentially very large surf next weekend (mainly down south, though some waves in the gulf)

Recap

The Mid Coast has maintained 2-3ft surf for the last few days though moderate onshore winds have kept conditions on the bumpy, wobbly side of the coin. Tuesday offered excellent clean surf at Victor Harbor with clean 3-4ft sets and offshore winds, building to 5-6ft today though with early NW winds swinging W’ly mid-morning and blowing out most beaches. 

Bowls at the Bay on Tuesday! 

This week (May 8 - 9)

Today’s strong groundswell is expected to peak overnight or early Thursday morning before easing slowly through Thursday. 

Fortunately, high pressure will move in and rapidly ease local winds, so apart from some lingering lumpiness, we should see improving conditions across all coasts (more quickly on the Mid than down south, mind).

The Mid Coast looks to be the pick overall with fun 2-3ft sets across the reefs, easing from a less consistent 2ft to 1-2ft on Friday. 

Victor still looks pretty good for Thursday despite some early wobble. Early 6ft+ sets will ease to 4-5ft through the day but there should be enough size for some good waves across the more sheltered spots like The Dump and Chiton, with size abating further to 3-4ft on Friday under similarly light winds and clean conditions. 

In actual fact, we may even revert to a classic morning NE arvo SE wind combo through the day so aim for a morning session to improve your chances of the best conditions. 

This weekend (May 10 - 11)

Generally light variable winds are expected all weekend across both coasts. At this time of the year sea breezes become less common on the Mid Coast so we can expect clean conditions for most of the day, though with no new swells in the water it’s a moot point (just a few small residual 1ft sets if you’re lucky on Saturday, likely smaller on Sunday).

Down south, the typical wind regime under this high pressure pattern is early light NE and light to moderate afternoon SE, so once again, aim for a morning paddle both days for the best options.  

A small reinforcing swell is still expected on Saturday, originating from a broad pre-frontal W/NW fetch developing in the Southern Ocean now, below Western Australia.

Even though the fetch is poorly aligned, it is quite broad, long and strong, and will be working on the active pre-existing sea state from the current frontal progression, which should assist swell generation that'll spread back up into the mainland. 

Surf consistency from this source won’t be high however I’m still expecting the Middleton stretch to see occasional 3ft+ sets on Saturday, before size eases to 1-2ft throughout Sunday (expect bigger waves at the regional swell magnets).

Next week (May 12 onwards)

Smaller, residual swells will pad out the first few days of next week thanks to an inactive storm track through the Southern Ocean from later this week into the weekend. Weak high pressure over the state will maintain light winds so it’ll be an ideal time to scope out the exposed swell magnets for some fun small waves. 

Later Monday and early Tuesday, a new long period swell may reach the coast, generated by a small but tight low passing near Heard Island tomorrow. However the small fetch length and enormous travel distance means it probably won’t eventuate in much size throughout the region. The only reason it’s worth mentioning is because with locally light winds and a lack of significant pre-existing swells, it’ll probably be noticeable at the wave buoys with a jump in peak period to 18+ seconds - so my point is, don’t get excited about it - if we’re luck we’ll see a few one foot sets on the Mid and 1-2ft at Middleton, every fifteen or twenty minutes. 

Interestingly, a slightly better swell generated by the latter stages of this low (passing under Australia on Sunday and Monday) will generate a better SW tending S/SW swell for Wednesday that could produce some slow 2-3ft sets at Middleton. Unfortunately, the direction won’t favour the Mid Coast so continuing small surf is the most likely mid-week outcome in the gulf. 

Thursday onwards is where things start to become more interesting.

Another strong conveyor belt of Southern Ocean fronts will develop around Heard Island on Sunday and move through our swell window, but this time they’ll strengthen closer to the mainland. Fortunately they’ll also ride just north enough up into the Mid’s swell window to allow for small waves in the gulf. I’m expecting occasional 2ft+ sets on the more favourable parts of the tide on Thursday from this source. 

At Victor, wave heights should build into the 4ft range at Middleton, and early indications are for light winds across both coasts.

We’re then looking an amplification of the Long Wave Trough into next weekend that’s on track to deliver a very large swell across the South Coast, if current model guidance holds true (see below) we could be looking at 8-10ft sets (or more!), though it’s still a very long time away - and, the eastern longitude of this intensification isn’t suitable for the Mid either. So let's be cautious for now with our expectations, but pencil it into the diary. 

I’ll have more on that in Friday’s update. See you then!