textproduct: San Diego

SYNOPSIS

A slight chance of showers and thunderstorms will continue into this morning, mainly for the mountains and deserts of San Bernardino County. A low pressure system to the north will bring stronger onshore flow and a cooling trend for Thursday through the weekend with Sunday high temperatures near the coolest for the date for a few locations. Southwest to west winds for the mountains and deserts during the afternoon and evening will strengthen for Thursday through Saturday, then weaken for early next week. The marine layer will deepen late in the week into the weekend with night and morning coastal low clouds extending well inland and onto the coastal slopes of the mountains for early Saturday. Then warmer for early next week, but with high temperatures remaining below average.

SHORT TERM (Today through Friday)

A slight chance of showers and thunderstorms will continue into this morning, mainly for the mountains and deserts of San Bernardino County, before southwest flow aloft brings drying for this afternoon. A low pressure system moving southward just off the coast of British Columbia will strengthen the onshore flow across southern California for Thursday through the weekend with a cooling trend.

High temperatures for today will be within a few degrees of average for most areas and around 5 degrees above average for the deserts. High temperatures for today will range from the lower to mid 70s near the coast to the mid 80s to mid 90s for the Inland Empire with 108 to 112 for the lower deserts. With the cooling on Thursday and Friday, high temperatures on Friday will will be as much as 5 to 10 degrees below average for the Inland Empire. High temperatures on Friday will range from around 70 near the coast to the 80s for the Inland Empire with 102 to 108 for the lower deserts.

The marine layer will be around 2000 feet deep with night and morning coastal low clouds spreading into portions of the western valleys late each night. As onshore flow strengthens, southwest to west winds for the mountains and deserts during the afternoon and evening will strengthen on Thursday and Friday with gusts to 30 to 40 mph and with gusts to 65 mph in the northern Coachella Valley below the San Gorgonio Pass.

LONG TERM (Saturday through Tuesday)

High temperatures will cool another 5 degrees for inland areas on Saturday and a few more degrees for most areas on Sunday. Sunday high temperatures will be as much as 12 to 18 degrees below average for the mountains and Inland Empire with high temperatures ranging from around 70 near the coast to the mid 70s to lower 80s for the Inland Empire with the mid to upper 90s for the lower deserts. High temperatures for a few locations on Sunday could be near the coolest for the date.

High temperatures will begin to warm next week with Monday a few to around 5 degrees warmer than Sunday. Slower warming of a few degrees per day will continue for Tuesday and Wednesday. High temperatures on Tuesday will still be as much as 8 to 12 degrees below average for the mountains and inland valleys with high temperatures ranging from around 70 near the coast to the upper 70s to mid 80s for the Inland Empire with the upper 90s to 102 for the lower deserts.

The marine layer will deepen to around 4000 feet by early Sunday with night and morning coastal low clouds extending well inland and onto the coastal slopes of the mountains. The marine layer will begin to decrease in depth early next week with coastal low clouds for early Tuesday extending inland into portions of the inland valleys.

Onshore flow will be strongest on Saturday with southwest to west winds for the mountains and deserts during the afternoon and evening gusting to 35 to 45 mph with gusts to 75 mph in the northern Coachella Valley below the San Gorgonio Pass. The ECMWF Extreme Forecast Index has these winds in the 80th to 90th percentile for this time of the year, locally to the 95th percentile. The winds will begin to weaken on Sunday with greater weakening early next week.

AVIATION

240930Z...Coast/Valleys...Low clouds with bases 1000-1500ft MSL have crept into coastal areas under mid/high level clouds AOA 20000ft MSL. Due to these upper level clouds, low level cloud formation will be patchy and intermittent at times. Low clouds will clear land areas 16-17Z. Expect low clouds with similar bases returning after 03-04Z Thursday with better coverage.

Mountains/Deserts...VFR conditions expected through the TAF period with SCT-BKN high clouds AOA 15000ft MSL. Mid to upper level clouds will clear the area by 22-23Z giving way to mostly clear skies.

MARINE

No hazardous marine conditions are expected through Monday.

BEACHES

Surf will continue to increase this evening with the arrival of a 3 foot 15 to 18 second period south swell from 190 to 210 degrees. Surf of 4 to 6 ft is expected through Thursday. Expect locally hazardous swimming conditions and strong rip currents through the week. See the Beach Hazards Statement for more details.

SKYWARN

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

SGX WATCHES/WARNINGS/ADVISORIES

CA...Beach Hazards Statement through Thursday evening for Orange County Coastal Areas-San Diego County Coastal Areas.

Red Flag Warning until 11 AM PDT this morning for Victor Valley -Apple Valley -Lucerne Valley -Johnson Valley.

Extreme Heat Warning from 11 AM this morning to 8 PM PDT Thursday for San Diego County Deserts.

PZ...None.