South Australian Surf Forecast by Ben Matson (issued Monday 27th March)

Best Days: Tues: fun lumpy surf on the Mid. Becoming wind affected Wed. Tues/Wed: initially small but steadily building swells at Victor with mainly favourable winds. Thurs: very large surf at Victor though with onshore winds. Fri: improving condition at Victor with large easing swells. Thurs/Fri: fun small waves on the Mid though less confidence as the swell direction swings more S'ly. Sat/Sun: another very large swell for Victor though winds could be an issue.

Recap: Long period swell energy built slowly across the coast all weekend, though Saturday saw onshore conditions across the South Coast ahead of a clean day of waves on Sunday. The Mid Coast saw small waves building on Sunday and conditions were generally clean here too. Today, gusty onshore winds have kicked in before dawn so conditions are choppy on the Mid Coast with a building W'ly swell, whilst conditions are slowly deteriorating down south, though the W’ly component in the wind direction is allowing for workable conditions at some locations. Surf size is small here because of the W'ly swell direction.  

This week (Mar 28 - 31)

We’re still on track for a very large, powerful swell to arrive mid-late week. But there are several stages of swell ahead and with a tricky wind outlook we need to hone into the specifics.

The developing frontal progression through the Southern Ocean is broad, and encompasses a couple of surface low pressure centres. The first is a cut-off low in the Bight, and is crossing the SA coast right now. This system is riding high in the Bight and its swell generating fetch is tucked up tight inside our acute western swell window, so it’s generating surf mainly for the Mid Coast - it’s too westerly for Victor (evident by the small size there today). 

This swell is already starting to show across the Mid Coast and should hold into Tuesday with 2-3ft+ sets (upper end of this size range on the afternoon tide). Today’s onshore flow will ease right back so we are looking at fun, lumpy waves for much of the day - winds may veer W/NW throughout the day but on the whole it’ll be worthwhile.

Conditions will remain reasonably clean at Victor on Tuesday as the wind tends more W/NW but wave heights will initially be limited to an inconsistent 2-3ft at Middleton, and 4ft+ sets at Waits and Parsons.

While this is happening, a deep polar low SW of Western Australia will have have extended a broad fetch to merge with the cut off low in the Bight, and the resulting swell generating system looks to be a doozy - a couple of thousand kilometres of W thru SW gales across the Southern Ocean.

With the merged fetch being positioned a little further south, this will allow for more SW in the swell direction, so solid sets may start appearing across the South Coast into Tuesday afternoon (4-5ft Middleton, 6ft+ Waits/Parsons etc). However this is more likely to develop through Wednesday. Conditions should be good through Wednesday morning under a freshening NW breeze but a SW change is expected at some point with another frontal passage, so keep this in mind. 

Wednesday on the Mid looks similar to Tuesday with a mix of old and new swell, and size up to 2-3ft+ on the more favourable parts of the tide, but onshore winds could create some problems here and there as we’re looking at freshening W/NW tending SW breezes (they’ll become quite gusty later).

The real juice will kick in on Thursday; this energy will be sourced from the polar low itself which will be trailing at the back end of the fetch though will be working on the active sea state generated by three days of westerly gales prior. 

Unfortunately, we’ll be under a post-frontal SW airstream on Thursday which will largely chop up conditions at Victor. Wave heights should reach a solid 8ft+ (!) at exposed spots so there’ll be sizeable options for those who enjoy the big stuff. Winds won’t be too strong though so it’ll be workable at various locations.

Thursday’s swell should maintain 2-3ft+ surf across the Mid but confidence is a little less for this pulse as the swell direction will be slightly more south than the previous swells, which may shave off a little bit of size. So I won't be overly surprised if it comes in slightly under expectations. But local winds should actually be quite good across the Mid on Thursday; likely moderate S/SE at times. I’ll update this outlook on Wednesday.

We’ll then finish the week off on Friday with large but steadily easing swells down south, from 6ft+ down to 4-5ft throughout the day at exposed spots, and light variable winds keeping condition clean. Conditions will also remain favourable across the Mid Coast with inconsistent 2ft+ sets on offer. 

This weekend (Apr 1 - 2)

The interesting thing about this week’s upcoming swell on Wednesday, Thursday and Friday is that it'll probably be a distraction for a likely better swell inbound for the weekend. So don’t over-froth too hard over the coming days as there’s more to come.

A deepening polar low is expected to reach maturity well south of WA (off the Ice Shelf) from late Wednesday through Thursday, and wind strengths are likely to max out in the 60kt+ range (check the MSLP and 10m wind chart below!). Whilst smaller in length and size than the mid-week system, the more southern AND eastern position of this low means that the resulting swell will have more south in direction (i.e. SW tending S/SW).

This is a great position for the South Coast but not very good for the Mid Coast. So, expect small surf in the gulf and large waves across south facing coasts like Victor Harbor.

Surf size is expected to build all day Saturday and should reach 8ft at exposed locations by the afternoon, easing from 6ft+ Sunday morning. We should see occasional 1-2ft waves along the Mid Coast from this swell.

Winds look a little problematic for the South Coast on Saturday thanks to a moderate S’ly flow developing around a new high pressure system, but its early days right now and there’s a chance we could end up seeing light variable winds if the high moves a little further to the east. Similar conditions are expected Sunday.

Next week (Apr 3 onwards)

Looks like plenty of fronts will develop in the Southern Ocean beyond this so the middle to latter part of next week is also shaping up very nicely for South Australian surfers.