textproduct: San Diego

SYNOPSIS

A series of Pacific storms will pass by to the north today and Friday bringing gusty westerly winds in the mountains and deserts. An upper ridge will build from the southwest late Friday through the weekend. This will result in mild days, a shallow marine layer, and cool nights this weekend. Some offshore flow could develop early next week after another trough of low pressure passes by to the north and northeast.

DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE

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

Scattered high clouds continue to move across the region early this morning as a mostly zonal Pacific jet remains aimed at central and northern California. A pair of short waves will move by to the north today and Friday, maintaining mild weather, though highs remain several degrees above normal in the deserts. Gusty westerly winds will develop across the mountains and deserts late Thursday night into Friday, peaking Friday afternoon and evening with gusts around 35-45 mph on the wind prone desert mountain slopes and below the passes. Winds will diminish Friday night. Increasing onshore flow will also bring the return of the marine layer along the coast late tonight or Friday morning, though with the passing trough it should deepen fast enough to mitigate any dense fog concerns. In fact, by Friday evening it could even be deep enough for some spotty drizzle west of the mountains.

The subtropical high to our southwest will slowly shift eastward and expand into Southern California this weekend, bringing warmer weather and causing the marine layer to become more shallow. Highs in the inland valleys through the deserts will be around 7 to 15 degrees above normal, with highs closer to normal for the coastal areas and western valleys as some marine layer influence remains. By Sunday morning the marine layer could be shallow enough for another round of dense fog in the coastal areas.

Surface pressure gradients begin to trend offshore on Monday following the passage of another wave to our north. There are some timing and strength differences in the ensembles, but for now it looks likely for a period of weak to potentially moderate (20% chance) Santa Ana event sometime in the Monday-Wednesday time frame, bringing warmer and much drier conditions. NBM 90th percentile high temperatures have highs reaching the low 80s in the valleys on New Year's Day.

AVIATION

261000Z....SCT-BKN high clouds at or above 20,000 ft MSL will continue to stream south across the region through this evening. Low clouds develop tonight, remaining mostly offshore, with minimal chances for CIGs at any site (10-20% chance) through Friday morning. Periods of stronger westerly winds up to 25 knots possible in the high deserts and near the mountains with mod up/downdrafts on Friday.

MARINE

After the current swell wanes this morning, another series of long period west-northwesterly swells pick up Friday and continue through the beginning of next week. Seas will be generally 5-9 feet in the outer coastal waters and 3-6 feet in the inner waters. Northwest flow will strengthen slightly late Friday afternoon, with areas of gusts around 20 knots near San Clemente Island. Otherwise, no marine hazards are expected through Monday.

BEACHES

As the long period west-northwest swell fades, surf heights continue to wane, but locally high surf of 5-9 feet remains possible for west facing beaches in San Diego County through this afternoon. This will make swimming hazardous and pose a minor coastal flooding threat. See the High Surf Advisory for more details.

After a brief lull late today into Friday, another long period (15 to 17 seconds) northwesterly (280 degree) swell of 3-5 feet arrives. Elevated surf to 4-6 feet is expected late Friday through early next week with localized sets to 7-8 feet possible on west-northwest facing beaches. Minor coastal flooding is possible for vulnerable areas during morning high tides as tides increase through this weekend coinciding with the elevated surf.

SKYWARN

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

SGX WATCHES/WARNINGS/ADVISORIES

CA...High Surf Advisory until 4 PM PST this afternoon for San Diego County Coastal Areas.

PZ...None.