COOS BAY — The first major storm of the season is on its way.

One smaller front came through Thursday, bringing some warm gusty winds in the afternoon and leaving about a quarter of an inch of rain in its wake.

But now, as a low pressure system moves across the Pacific, the associated fronts are forecast to bring fairly big seas, some high winds and yes, that Oregon icon, rain, to the South Coast tonight and Saturday. The rain likely will continue through Tuesday, tapering off at the beginning of next week.

As usual, the storms bringing southerly winds and swells break the summer’s tradition of cold northwest winds. They will be accompanied by fairly warm temperatures of nearly 70 during the day and overnight lows in the mid-40s to low 50s.

The real action will be on the ocean.

“This is a significant storm,” National Weather Service spokesman Ryan Sandler said Thursday.

South winds associated with the warm front moving through the coastal waters today will increase to between 40 and 45 mph, with gusts to 50 and even greater near Cape Blanco, near Port Orford.

At the same time, seas will build today to between 11 and 14 feet at 8-second intervals — steep waves that pack a lot of water and a lot of power. On Saturday, though, stronger and bigger westerly swells of 16 feet at 12 seconds will come ashore.

Though bigger, the forecasted swell heights are lower than what the NWS forecast Thursday. At the time, 20-foot swells were expected.

Regardless, the big waves could mean trouble for beach visitors.

“This will create hazardous surf conditions that can endanger anyone near the surf zone,” the NWS said in a special weather statement today. “Large waves of this nature often catch people by surprise, sweeping them from jetties and beaches into the surf. As surf heights increase, dangerous rip currents develop which make it difficult to get back to shore if caught in the surf.”

The NWS has posted a hazardous seas warning in effect through 11 a.m. Sunday and a gale warning for the nearshore waters until 2 a.m. Saturday.

A high wind warning also is in effect for the South Coast, including all the cities from Coos Bay to Harbor, until 2 a.m. Saturday. Sustained winds of at least 40 mph or gusts of 58 mph can lead to property damage, the NWS said.

Often, the winds can uproot trees, especially if the ground is saturated by rainwater. That hasn’t happened yet this year, the NWS, but that doesn’t mean there couldn’t be tree damage.

“This is only the second system following a prolonged dry period and this moisture has not had time to percolate down to loosen the larger tree roots,” the NWS said in its high wind warning statement. “This same prolonged dry period means that trees are currently at the highest stress and still will mean a high possibility of branches and even trees breaking with the high winds and bringing down power and phone lines along the coast and some areas a bit inland.”

By Sunday, winds should subside and swell heights are expected to drop to around 8 to 11 feet, before a high pressure system moves in and brings with it swells and winds out of the northwest again next week.