textproduct: San Diego

SYNOPSIS

Patchy dense fog is expected on the coastal mesas and western valleys this morning. High pressure and weak offshore flow will continue to bring fair weather and above normal temperatures through Friday, with cooler weather this weekend. Coastal low clouds and fog will continue each night and morning, but less so Tuesday through Thursday with more coverage Friday through the weekend.

DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE

SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES...

With a slightly deeper marine layer this morning, the dense fog is not as widespread as it has been previously. Still, pockets of dense fog can be expected on higher coastal mesas and western valleys this morning, so be aware and plan accordingly, especially if you travel on the 91 or 241 in OC into Riverside County or the 15 in San Diego County. Otherwise, look for another sunny and warm day, especially away from the coast. Offshore flow will increase a little today, producing localized northeast winds through Tuesday morning in the usual foothill areas through and below mountain passes. Isolated top gusts could reach 30-40 mph. This offshore flow will push back on the marine layer, reducing coverage of coastal clouds and fog for tonight and Tuesday morning. Our large scale weather pattern features a strong, active zonal flow, which has brought and will bring heavy rain to WA, OR. The next shortwave through that region will help turn flow here in SoCal briefly onshore Tuesday night and Wednesday, bringing back more coastal fog and also briefly boosting winds in the mountains and deserts, particularly the high desert late Wednesday. The flow trends offshore again Wednesday night and Thursday before turning weakly onshore again Friday. This time the onshore flow appears to remain for the weekend and beyond, with coastal clouds probably reaching into some valleys nights and mornings. Temperatures will fluctuate, especially west of the mountains, as the surface flow oscillates from onshore to offshore and back again. Right now Tuesday and Thursday look like the warmest days in the coming week, with high temps inland reaching 15-20 degrees above average for this time of year, and 5-10 degrees above average at the coast. Even the cooler days this week will continue well above average regionwide. That zonal jet stream to our north will slowly but steadily sag southward next week, tapping into some subtropical moisture along the way. Confidence is understandably low in any forecast that far out, but if the majority of current ensemble solutions are right, SoCal would get some rain by the time Santa Claus arrives.

AVIATION

150930Z...Coast/Valleys...Low clouds based 300-800 feet MSL have pushed into inland Orange County and into the valleys of SD County. BR/FG reducing VIS to 0-2SM for these inland areas, elevated coastal terrain and the Chino Valley. Patchy BR reducing VIS 1-4SM at the immediate coast, with periods of VIS below 1SM after 10z. With offshore flow locally this morning, clouds begin to scatter and VIS to improve 15-17z in some areas with full clearing to the coast not until 18-20z. Low clouds with bases 200-600 ft MSL and FG slowly develop and begin pushing up to 10 miles inland from the beaches 00- 02z Tue, in very patchy fashion. Areas of BR to lower VIS 2-5SM and patchy FG to reduce VIS to 1/4SM locally.

Mountains/Deserts...Clear skies and VFR conditions expected through Tuesday morning with FEW high clouds late Monday.

MARINE

Low clouds will bring areas of low visibility around 2-5 nautical miles through early Monday afternoon. Seas rise briefly to 5 to 7 feet in the outer waters Wednesday afternoon through late Thursday. Otherwise, no hazardous marine conditions are expected through Friday.

SKYWARN

Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions.

SGX WATCHES/WARNINGS/ADVISORIES

CA...None. PZ...None.