textproduct: San Diego

SYNOPSIS

Cooler through Thursday with highs returning to normal. Gusty southwest to west winds continue across the mountains and deserts through Thursday, peaking on Wednesday. There is a chance of light showers late Tuesday into Wednesday morning. Friday through next weekend will be warmer and drier with high temperatures warming to 10 to 15 degrees above average for inland areas next Sunday.

DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE

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

Evening update... Widespread high clouds continue to move over the region this evening. Marine layer low clouds have returned to the coastal areas and will spread into the inland valleys overnight as the marine layer deepens. There could be some spotty light drizzle for the coastal areas and valleys tonight with the deepening marine layer. Otherwise gusty southwest to west winds continue tonight across the mountains and deserts with gusts up to 35 mph below the favored passes and desert mountain slopes.

Previous discussion... A low pressure system currently about 1000 miles off the coast of NorCal will move inland over SoCal late Tue into Wed. Strengthening onshore flow will bring gusty southwest to west winds through Thursday. These winds will be strongest late Tue through Wed in the mountains and deserts where wind gusts of 35 to 45 mph are likely today and Tuesday becoming 45 to 55 mph for late Tuesday night and Wednesday.

As the onshore flow spreads cooler marine layer air farther inland, Wednesday will likely be the coolest day with high temperatures generally within a few degrees of seasonal averages. Temps will range from the upper 60s to around 70 near the coast to the lower to mid 70s for the valleys and inland Orange County with the lower deserts in the 80s.

This system will also bring deep-layer moisture and more widespread clouds, with chances for light showers from the mountains to the coast. The deserts will likely remain rain- shadowed. Current precipitation estimates are for less than one tenth inch to near two tenths inch in the San Bernardino Mountains. Elsewhere from the coast to the mountains, a few hundredths of an inch or less is expected. The snow level will be mostly above 8000 to 8500 feet through Tuesday night, lowering to around 7500 feet by Wednesday morning.

This system will be followed in short order by a more intense low pressure system moving inland farther north, with a closed upper low moving east over WA/OR Thu-Fri. This will sustain the strong onshore flow through Thursday but as the low pressure system moves eastward into the Rockies, a surface high will move into the Great Basin setting up offshore flow for Fri and Sat. We are likely to see some Santa Ana winds Fri-Sat but the strength of the winds is uncertain at this time.

Next Sunday will likely be the warmest day with a ridge of high pressure bringing daytime temps of 10-15 degrees above seasonal averages west of the mtns and in the deserts. A return of onshore flow will bring lower temperatures to areas west of the mtns but the deserts will remain warm, with temperatures in the mid to upper 90s.

AVIATION

310400Z...Low clouds 1500-2000 ft MSL are slowly covering the lowlands of SD and Orange Counties, developing into the Inland Empire 06-10z, increasing in coverage throughout the night. VIS 0- 5SM where terrain and clouds meet in the foothills. Cloud bases gradually increase overnight, reaching 2000-3000 ft MSL by 16z throughout the coastal basin with patchy -DZ possible at the coast.

Low clouds may scatter at times after 19z but remain SCT-OVC most of the day, with mid-level BKN-OVC clouds at 7-10kft MSL above across the region. Chance (15-25%) for spotty -RA across the coastal basin after 18z, locally higher chances in the western foothills/mountains. Bases fill in coverage after 01z Wed across the coastal basin, 1500-2500 ft MSL.

Otherwise, VFR conditions prevail for most of the region.

MARINE

No hazardous marine conditions expected through Wednesday. Northwest winds increase Thursday to near 20 kts.

SKYWARN

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

SGX WATCHES/WARNINGS/ADVISORIES

CA...Wind Advisory from 8 PM Tuesday to 11 PM PDT Wednesday for Apple and Lucerne Valleys-Coachella Valley-Riverside County Mountains-San Bernardino County Mountains-San Diego County Deserts-San Diego County Mountains-San Gorgonio Pass near Banning.

PZ...None.