Swell Matrix

Area Forecast Discussion

National Weather Service San Diego CA

930 am PST Fri Feb 23 2024

Synopsis

Dry, warm, with periods of breezy northeast to east winds today. Saturday, dry conditions remain with weaker northeast winds and slight cooling near the coast but further warming in the mountains and deserts. By Sunday, cooling will reach further inland with additional cooling expected each day through early next week. There are chances of rain and mountain snow early next week, along with periods of gusty westerly winds over the mountains, locally into the deserts.

Discussion

For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties, widespread high clouds across the area this morning. Periods of high clouds are expected at times today through much of this weekend. The high cloud coverage may delay daytime heating, but offshore flow this morning may help pockets of warmer air mix down from the atmosphere. Strongest wind gusts since midnight have been mostly 35 to 45 mph on the mountain foothills and below passes in the Inland Empire. Winds are expected to weaken into this afternoon. No updates have been made to the high temperature forecast this morning with highs expected to reach the 70s for much of the coast and valleys with the warmest locations for inland coastal areas into the western valleys in the upper 70s.

Saturday is expected to be dry as well, with weaker northeast to east winds in the morning. Highs will be a few degrees cooler than today for the coast and valleys but a degree or two warmer for the mountains and deserts. A trough approaching Southern California from the west and a trough digging south into the Great Basin from the Gulf of Alaska through British Columbia will begin to weaken the ridge over California and push it east on Sunday. This will spread cooler conditions further inland. That cooling trend will continue through at least the beginning of next week.

For Monday and Tuesday, a low pressure system will be moving southeastward through the Great Basin while the low pressure system that was well off the California coast weakens and moves inland through Baja and southern California. This will bring a chance of precipitation to southwestern California for Monday into Tuesday. Right now, ensemble guidance is indicating the bulk of the precipitation would fall Monday night into Tuesday morning.

The deterministic rainfall forecast ranges from one-tenth to one- quarter inch near the coast to one-third to one-half inch in the mountains with locally greater amounts. Snow levels would rise to 7500 to 8500 feet for late Monday, then fall to 6000 to 6500 feet on Tuesday. While around 10 percent of the ECMWF ensemble members still show fairly wet solutions, the overall trend is drier for Monday and Tuesday with the majority of members showing lighter precipitation. With the latest ensemble guidance, some members are beginning to show at least light precipitation each day for the middle to end of next week. This is solution is still in the minority but it does make it difficult to say with certainty that the middle to end of next week will be completely dry. If precipitation were to continue into the middle/end of next week, it would likely be isolated, light showers, most likely near the mountains.

Aviation

231640z, BKN high clouds at/above 20,000 ft MSL becoming SCT by the afternoon and evening. Unrestricted vis expected through Saturday. NE-E winds with gusts 20-30 kt will continue along the coastal slopes and below the passes through about 20Z, then weakening into the evening. MOD up/downdrafts and LLWS over and SW of the mountains.

More SCT high clouds and light winds expected on Saturday.

Marine

No hazardous marine conditions are expected through Sunday. Another storm will bring rain and gusty winds Monday into Tuesday morning. There is a 30-40% chance for west-northwest wind gusts 20-25 knots Tuesday morning into Tuesday afternoon, mainly over the outer coastal waters.

Watches, Warnings, Advisories

Ca, None. PZ, None.

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