textproduct: San Diego

SYNOPSIS

Below average temperatures with marine layer low clouds and fog reaching into portions of the valleys through Sunday. Gusty westerly winds expected in the mountains and deserts this afternoon and evening. Warming trend expected Monday through at least the middle of next week. Areas of major HeatRisk possible for the deserts and moderate HeatRisk for inland Orange County, valleys, and mountains mid next week. The marine layer will become shallower next week, staying confined to coastal locations.

DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE

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

The marine layer was slightly shallower this morning down to 2500 ft from 3000 ft yesterday. That did not hamper the inland extent of the cloud coverage this morning, with satellite imagery this morning showing low clouds in the entire coastal basin and through the Cajon Pass. The inversion on the 12Z sounding from KNKX was a little weaker than yesterday, which has helped the speed of clearing. There are also higher chances of the beaches clearing this afternoon.

High temperatures through the weekend will be below average for most locations due to a passing trough. In addition to cooler conditions (and the deeper marine layer), elevated southwest to west winds can be expected. Gusty winds this afternoon and evening for the mountains and deserts will reach gusts of 30 to 40 mph and with local gusts to 55 mph in the northern Coachella Valley below the San Gorgonio Pass.

A more zonal patter on Monday will result in a few degrees of warming, with continued warming for the area through at least mid- week as an area of high pressure aloft builds over the southwest US and drifts west over California. Current forecast follows the NBM for Tuesday through next Thursday which will bring high temperatures 5 to 12 degrees above average with areas of moderate HeatRisk away from the coast and areas of major HeatRisk in the low desert. Hottest conditions based on current forecast are expected to be Tuesday through Thursday. Ensemble guidance is also indicating an increase in precipitable water for the middle to end of next week. That would result in warmer than normal overnight low temperatures, limiting overnight relief from the heat and making it feel humid. As far as the marine layer goes, the building high pressure and influx of moisture will result in a shallower marine layer and limited low cloud development.

The spread in potential forecast solutions starts to increase for the middle to end of next week. Ensembles are indicating the possibility of a shortwave trough moving through California during the middle to end of next week, which would result in increased onshore flow and cooler conditions, especially for the coasts and valleys. By Thursday, the spread in NBM high temperatures is 9 to 11 degrees between the 10th percentile of guidance (cooler) and 90th percentile (warmer. Depending on how the upper level pattern develops, there is a potential for the above average conditions and elevated HeatRisk to continue into the end of next week for inland locations.

AVIATION

191830Z...Coast/Valleys...Low clouds based around 2500 ft MSL currently lingering in Orange County and the northern Inland Empire will scatter out by 19-20z. Clouds redevelop starting 00-02z over coastal San Diego County with bases 2000-2500 ft MSL. Clouds will spread northward and inland late this evening and overnight, filling the coastal basin entirely by 10-12z Sat. Low clouds scatter out toward the coastline 16-19z Sat.

Mountains/Deserts...VFR conditions expected through the TAF period. Breezy westerly winds with gusts 25-40 kts return after 21z for desert slopes and deserts. Gusts up to 50 kts through the Banning Pass and into the northern Coachella Valley along with minor vis reductions in BLDU. Moderate up/downdrafts in lee of mtns. Winds slowly taper off 06-12z Sat.

MARINE

No hazardous marine conditions are expected through Wednesday morning.

BEACHES

Elevated surf and strong rip currents continue through Sunday and potentially beyond. Surf of 3-5 feet with local sets to 6 feet are expected at south-facing beaches. Expect locally hazardous swimming conditions with high rip current and longshore current risk. See the Beach Hazards Statement for more details.

SGX WATCHES/WARNINGS/ADVISORIES

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

PZ...None.