textproduct: San Diego

SYNOPSIS

Onshore flow through Thursday morning will allow for the return of patchy low clouds and fog at the coast tonight. Strong ridging in combination with weak offshore flow will create well above average temperatures for Thursday through Saturday. Friday will be the warmest day with record highs likely for several inland valley locations. On Saturday, winds turn back onshore and the ridge begins to weaken as a weak upper low approaches from the west. This will allow for increasing cloud cover and a return to near normal temperatures by early next week.

DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE

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

High clouds in the current visible satellite loop depict a broad upper ridge over the western CONUS. A shortwave trough passing well to the north will go almost unnoticed across the area, with just enough forcing for westerly wind gusts 25-35 mph across the High Desert and through mountain passes this evening. Also, increased onshore flow presents a 50-60% chance for low clouds (and fog) to finally return over coastal waters and coastal land areas tonight.

The main story in the near term is the temperatures, which are expected to run well above normal through Saturday. The upper ridge will continue to strengthen through Friday with its axis centered right over Southern California. Concurrently, weak offshore flow will develop for Thursday into Friday. This will allow temperatures to soar 10 to 25 degrees above normal area wide Thursday through Saturday (locally 25 to 30 degrees above normal for inland valleys and coastal slopes). Friday will be the hottest day with multiple records set to fall across the inland valleys and mountains. Temperatures in the upper 80s to low 90s for inland valleys, 70s and 80s in the mountains, and mid to upper 90s for the low deserts. Well above average temperatures linger through Saturday, but the return of onshore flow and a weakening ridge should knock temps down a few degrees relative to Friday.

Onshore flow strengthens and the ridge weakens further by Sunday as a weak upper low pushes in from the west. This will bring breezy conditions for the mountains and deserts, an increase in cloud cover, and a return to near normal temperatures by early next week. Guidance varies some on the exact track of the low, but most solutions remain dry as the low passes through. Chances for measurable precip remain below 15 percent through early next week.

Models diverge quickly by mid next week, but there is there is some indication of weak troughing with another low pressure system affecting the west coast late next week. Whether or not Southern California is affected remains to be seen.

AVIATION

260400Z...Coast...Patchy FG to lower VIS below 1SM at times for coastal sites after 10z tonight. Most likely timeframe for periods of VIS down to 1/4SM around 11-15z for coastal areas, including KSAN/KCRQ/KSNA. Cigs around 200-500 feet MSL. Localized areas of valley FG as well for inland areas overnight with near zero VIS. Clearing after 16z but patchy stratus may linger at the beaches into the early afternoon. Thursday evening, low confidence and low chances (20-30%) for FG to move into coastal areas.

Inland Valleys/Mtns/Deserts...VFR conditions through through the period for inland areas with SKC-FEW250.

MARINE

No hazardous marine conditions expected through Sunday.

SKYWARN

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

SGX WATCHES/WARNINGS/ADVISORIES

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