Low Front Puts Pressure on High Humidity

More warm weather and high humidity are forecast for today, fed by a low pressure system stuck over northern Baja California that is bringing moist air over San Diego County.

Wilbur Shigehara, chief meteorologist for the National Weather Service at Lindbergh Field, said that today’s weather will be a carbon copy of the sticky sort that left San Diegans feeling uncomfortable Friday and Saturday.

“What you will have on Sunday is just more of what you had today,” Shigehara said.

That means a 20% chance of afternoon and evening showers in the coastal and inland areas. In addition, temperatures are expected to be a little bit higher than usual, accompanied by unusually high humidity.

Shigehara said that Saturday’s high temperature registered 78 degrees at Lindbergh Field, which is one degree above normal for this time of year. However, the humidity registered 93% in the morning and dropped to only 73% by 4:30 p.m. Normally, the afternoon humidity drops to 65% in late September, Shigehara added.

“We can blame the moist air for this. It’s affecting the mountains, too. We expect thunder showers in the mountains again (on Sunday) during the afternoon and evening hours. The heat is the trigger mechanism for the thunder showers,” Shigehara said.

A surprise thunder storm Friday afternoon dropped about 0.24 inch of rain on Lindbergh Field. Scattered showers were reported throughout the county on Saturday, but Shigehara said they amounted to traces of barely measureable rainfall.

He predicted a cooling trend for Monday and Tuesday, when temperatures are expected to drop to about 66 degrees with lower humidity. Monday is also the first day of autumn.