South Australian forecast by Craig Brokensha (issued Wednesday April 16th)

Best Days: Both coasts Friday, South Coast Saturday morning, South Coast Wednesday morning, South Coast Thursday morning

Features of the Forecast (tl;dr)

• Moderate sized W/SW swell building later tomorrow, peaking Fri AM
• Variable offshore winds tomorrow ahead of sea breezes
• Variable offshore winds Fri ahead of weak sea breezes (variable Mid Coast)
• Easing swell Sat with strengthening N/NW tending W/NW then W/SW winds
• Building windswell across both coasts Sun with strong W/SW-SW winds
• Easing swell Mon with mod-fresh S/SW winds (S/SE on the Mid early)
• Very inconsistent, moderate sized SW groundswell building Tue PM, peaking later and into Wed AM
• E/NE tending SE winds Tue, NE tending SE Wed
• Easing swell into the end of next week with N/NE morning winds

Recap

The Mid Coast backed off to a tiny 1ft through yesterday with clean conditions all day, similar in size this morning but with a few small imperfections.

The South Coast was a fun 2ft+ yesterday off Middleton, much better across the exposed beaches while a reinforcing S/SW groundswell due today has come in a little undercooked with inconsistent but clean 2ft+ waves continuing across Middleton.

This week and next (Apr 17 - 25)

Looking at tomorrow, and we should see a good new W/SW swell filling in during the afternoon, with a peak expected Friday morning across the state.

As mentioned earlier in the week, the source was a strong polar frontal progression that projected up and then under Western Australia earlier this week, weakening yesterday.

Fetches of strong to gale-force W/SW winds should produce 1-2ft waves into later tomorrow on the Mid Coast, peaking to 2ft on the favourable parts of the tide Friday with the South Coast building later tomorrow to 3ft with 3-4ft sets across Middleton Friday.

Local winds tomorrow look variable offshore on the South Coast ahead of sea breezes, more convincing offshore on the Mid ahead of relatively weak sea breezes.

Friday is the pick with light, local offshore winds that will tend variable on the Mid Coast and go moderate sea breezy down South.

The size will slowly ease into Saturday, slowed by a small reinforcing SW swell for the morning, generated by a weak fetch of strong to gale-force W/NW winds moving under WA today.

Middleton should ease back from 3ft with 1-1.5ft sets inside the gulf. Strengthening N/NW tending W/NW then W/SW winds will favour the South Coast while creating choppy conditions on the Mid Coast.

It looks like the trough linked to the winds through Saturday will stall Sunday, bringing strong W/SW-SW winds (likely W/NW for a period down South) kicking up a weak windswell for the Mid Coast to 1-2ft while the South Coast will also likely see some S/SW swell on the build but with no quality.

Monday will remain poor down South with moderate to fresh S/SW winds, cleaner inside the gulf with a morning S/SE’ly but with tiny levels of easing surf from Sunday.

Looking at Tuesday and a new, long-range and inconsistent SW groundswell is due, generated by a strong, mutli-staged low that’s formed to the south of South Africa.

An initial fetch of very distant, gale to severe-gales has now weakened, but a secondary polar front pushing up over the back of the initial low today is generating an additional fetch of gale to severe-gale W/NW winds that will project to about the Heard Island region tomorrow before weakening into the afternoon.

This will generate a very inconsistent SW groundswell that should build Tuesday and reach 3ft to occasionally 4ft across Middleton, holding a similar size Wednesday with the Mid Coast coming in at a tiny 1ft.

Local winds will slowly improve for the South Coast early next week with an E/NE breeze on Tuesday morning (ahead of the swell), better and NE on Wednesday.

Thursday and Friday both look clean as the energy eases with a possible strong Southern Ocean frontal progression firing up into next weekend. More on this Friday.