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

240530Z...Coast/Valleys...Patchy mid/high level clouds with bases 15000-20000ft MLS currently moving over the area. This cloud cover will result in patchy low cloud formation with bases expected between 1000-2000ft MSL. There are some patchy low clouds developing off coastal areas and are expected to move in along the coast after 07-09Z for SD and a 30-40% chance of formation after 09-11Z for OC. Low clouds clear land areas 16-17Z. Low clouds with similar bases are expected to return 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 mostly clear the area by 22-23Z giving way to predominately 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.

FIRE WEATHER

Mid-level moisture in southerly flow aloft will continue the slight chance of showers and thunderstorms into this morning, mainly for the for the mountains and deserts of San Bernardino County. Little if any rainfall will reach the ground and any thunderstorms that develop could produce dry lightning strikes and locally gusty and erratic winds. Dry lightning strikes could result in fire starts that have the potential for initially rapid growth. The flow aloft is expected to become southwesterly by the afternoon bringing drying aloft.

A low pressure system moving southward just off the coast of British Columbia will strengthen the onshore slow across southern California into the weekend. Southwest to west winds for the mountains and deserts during the afternoon will strengthen for Thursday through Saturday with gusts on Saturday of 35 to 45 mph with gusts to 75 mph in the northern Coachella Valley below the San Gorgonio Pass. Lowest humidity for the lower deserts will fall to around 10 percent for Thursday afternoon and Friday afternoon with near critical fire weather conditions for the deserts onto the desert slopes of the mountains for Thursday and Friday afternoon and early evening. The humidity for the deserts will begin to recover on Saturday with lowest afternoon humidity of 20 to 25 percent.

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 Today for Victor Valley- Apple Valley-Lucerne Valley-Johnson Valley.

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

PZ...None.