South Australian Forecast by Craig Brokensha (issued Friday 15th December)

Best Days: South Coast Saturday and Sunday mornings, Monday, Thursday both coasts next week, Mid Coast keen surfers Saturday and Sunday

Recap

Nothing to surf yesterday, while this morning there was a hint of new swell across both coasts with 1ft sets on the Mid and small inconsistent 1-2ft waves off Middleton with light winds. The swell has since built further down South though onshore winds are starting to develop.

We should see the new SW swell that's currently building reaching 3ft+ across Middleton late afternoon and 1-1.5ft on the Mid, though with those sea breezes.

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This weekend and next week (Dec 16 - 22)

This afternoon's increase in SW swell was generated by a frontal system pushing under the country the last two days, and should ease back slightly from a similar 3ft+ across Middleton tomorrow, with 1-1.5ft sets persisting on the Mid all day.

A reinforcing SW swell is due through the afternoon, produced by a secondary less favourably aligned fetch of strong WNW winds sliding through our swell window yesterday evening and this morning.

3ft sets are expected to persist across Middleton (1-1.5ft Mid Coast) through the afternoon, while one more reinforcing mid-period SW swell is due Sunday morning from a trailing fetch of relatively weak SW tending W/SW winds.

This should maintain 3ft sets across Middleton through most of Sunday before easing later, back from 2ft+ Monday morning. The Mid Coast should also maintain 1-1.5ft surf during the morning Sunday before fading Monday.

Winds tomorrow are now looking better and favourable for both coasts with variable breezes through the morning (likely tending locally offshore) before sea breezes kick in.

A swing in winds around to the E/NE and possibly NE is due Sunday favouring both coasts again, though certain locations down South over others.

Monday will be great at swell magnets as the swell drops away under a N/NE offshore.

Now, of greater importance is the interaction of a cold core low off the WA coast with a warmer inland surface trough as they both drift south-east across the Bight and into the Southern Ocean.

We'll see these systems combine resulting in the re-intensification of the low directly west and south-west of us, with a flurry of strong to gale-force W/SW and SW winds projected through our swell windows during Tuesday and Wednesday.

This should generate moderate to large amounts of mid-period W/SW and SW groundswell.

The Mid Coast will see the most size through Wednesday and Thursday, while the South Coast looks biggest through Thursday at this early stage. Winds are likely to drop away into Thursday as the frontal progression drifts south, but we'll have a closer look at all of this Monday. Have a great weekend!