textproduct: San Diego

SYNOPSIS

A cooling trend will continue through Friday. There will be chances of precipitation for locations over and west of the mountains Thursday through Saturday morning. Dry conditions are expected to return Sunday with a warming trend and periods of offshore flow expected into next week.

DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE

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

Widespread mid and high clouds cover the region this evening with a few low clouds west of the mtns. The lack of low clouds is likely due to a weak marine layer inversion allowing mixing of the marine layer air with the dry air above. The afternoon sounding also shows a dry layer from about 2,000-15,000 feet with increasing moisture above. Radar is showing echoes just west of San Clemente Island but any precip falling is not likely to reach the ground...yet.

From previous discussion... Onshore flow will strengthen as a low pressure system continues to move south parallel to the California coast before moving east into Baja California late Friday/early Saturday. The increased onshore flow will enable areas of low clouds and fog that develop overnight to reach well into the valleys and along coastal slopes of the mountains.

The low pressure system will also bring slight chances of showers to the area Thursday through early Saturday. Scattered showers could begin as early as Thursday morning, with rain likely continuing into Friday. About 50 percent of ensemble solutions keep the potential of rain over the area into at least Saturday morning. Latest high resolution guidance is indicating hourly rainfall rates will range from 0.05-0.25" per hour. Rates at or near 0.25" per hour will be fairly isolated and most likely occur Friday. Chances of rainfall totals exceeding 0.50" from Thursday through Saturday, are 10-20 percent for the coast and valleys and 30-40 percent in the mountains. The mountains have a 10-15 percent chance of exceeding 1 inch of rain. Snow levels will fall to 6500 to 7000 ft by Saturday morning. 1-3" of snow are expected around 7000 ft, with slightly higher totals expected above 8000 ft.

Today is trending cooler than yesterday, with further cooling expected into Friday. By the weekend, conditions west of the mountains are expected to warm a few degrees with continued cooling in the deserts. By Monday, widespread warming is expected with increasing temperatures each day into next Wednesday. Ensemble guidance is in agreement that a ridge of high pressure will set up over the West Coast on Monday and remain in place into next Wednesday. With the upper level low to our east by Sunday, offshore winds are expected to develop. Current ensemble guidance has an 80 percent chance of weak offshore winds developing, with a 20 percent chance of weak to moderate offshore winds developing.

Otherwise

Variable high clouds around 20 kft, lowering to around 10 kft by Thursday morning. Isolated -SHRA after 18Z Thu (more likely west of the mountains), but any impacts to cigs/vis should be minimal and brief if they occur.

MARINE

No hazardous marine conditions are expected through Monday.

SKYWARN

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

SGX WATCHES/WARNINGS/ADVISORIES

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