textproduct: San Diego

SYNOPSIS

Weakening Santa Ana winds today, with chances of light showers, mainly for the mountains tonight into Friday. Dry and warm over the weekend, with periods of weak Santa Ana winds. Pattern change expected next week, with chances of widespread precipitation.

DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE

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

This evening...Radar is showing weak, elevated convection moving to the northwest but most of the precip is evaporating in the deep and dry sub-cloud layer. In the last 6 hours, one location has reported measurable precipitation and that was 0.01 inch. Temperatures are generally lower than at this time yesterday, with some locations west of the mtns as much as 10-15 degrees cooler.

From previous discussion... Mid and high clouds are continuing to move northwest across the area due to a closed upper level low off the coast of northern Baja. The low is expected to slowly move northeast maintaining fairly widespread cloud coverage and bringing isolated to scattered light showers to the mountains and High Desert into Friday. Any rainfall accumulations will be light with the probability of rainfall totals exceeding 0.10" over 24 hours is 5 to 15 percent, highest in the San Bernardino mountains. Dry conditions will return for the weekend.

Substantial cooling is expected between today and Friday. Highs on Friday near the coast are expected to be 10 to 15 degrees cooler than today with highs further inland expected to be 5 to 10 degrees cooler than today. The cool down will be brief, with warmer conditions expected for the weekend. By Sunday, highs for inland locations will be back to 10 to 15 degrees above average. Along with the warm conditions, weak Santa Ana winds are expected for coastal mountain foothills and below passes. A change in the overall upper level pattern is expected for next week. The effects will be felt as early as Monday, with temperatures expected to be 3 to 5 degrees cooler than Sunday. Further cooling is expected through next week.

A broad troughing pattern is expected to prevail over the West Coast next week. This pattern will bring cooler conditions, the return of onshore flow, and chances of widespread precipitation. About 30 percent of global ensemble clusters have the low in position to bring us precipitation on Tuesday, with more guidance showing wetter solutions for Wednesday and Thursday. Most of the individual ensemble members are indicating mostly light rainfall amounts, with only a few members showing moderate amounts. There remains quite a bit of uncertainty in the details, especially when it comes to the timing of any precipitation. Please continue to monitor the forecast in coming days for more information.

AVIATION

060400Z....Coast/Valleys...Low clouds based 800-1500ft MSL will develop after 06Z and move inland in areas to 15-20 miles, with periods of IFR/MVFR CIGs at coastal TAF sites. Bases are expected to start out on the lower side then gradually rise overnight. Low clouds are expected to be patchy, which may result in periods of scattering out and conditions briefly returning to VFR. VIS generally should be above 5SM everywhere except where clouds intersect terrain. Low clouds scatter out 16-18Z Fri morning, then return after 02Z Sat at 1500-2500 ft MSL.

High clouds AOA 15,000 ft MSL continuing to stream over the area, moving out by early Friday morning. Slight chance of -SHRA mainly over mountains and deserts through about 12Z, except for through 00Z Sat for the San Bernardino Mtns, with cloud bases as low as 8000 feet MSL.

MARINE

A building northwesterly swell (280 degrees) at 15-16 seconds will bring seas of 6-9 feet in the outer waters near/around San Clemente Island Friday and Saturday. This may also lead to localized steep, rough conditions near the bay entrances, including the entrance to the San Diego Bay/Zuniga Shoal area. Otherwise, no hazardous marine conditions are expected through Tuesday.

BEACHES

Increasing long-period (15-16 second) swell from the west-northwest (280 degrees) will bring elevated to high surf of 5-8 feet with locally higher sets to 10 feet Friday afternoon through early Sunday morning. Impacts will be greatest at west facing beaches, especially across southern San Diego County, and there will be a high risk for rip currents. Further information can be found in the High Surf Advisory. This may also lead to minor tidal overflow for low-lying beach areas during high tide late Friday into early Saturday.

SKYWARN

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

SGX WATCHES/WARNINGS/ADVISORIES

CA...High Surf Advisory from 10 AM Friday to 6 AM PST Sunday for Orange County Coastal Areas-San Diego County Coastal Areas.

PZ...None.