textproduct: San Diego

SYNOPSIS

Weak to moderate Santa Ana winds will continue today. High temperatures 5-15 degrees above normal for the coastal areas and valleys today. Winds weaken into next week as high pressure moves into the area, keeping temperatures above normal. Gradual cooling with a 15-25% chance of precipitation late in the week.

..UPDATED AVIATION DISCUSSION

Skies are mostly clear this morning under weak offshore flow. Surface pressure gradients to the Great Basin have weakened significantly over the past 24 hr, though not much change has occurred to the Mojave Desert. Northeast to east winds are gusting 20-30 mph, mainly in the Cajon Pass and along the coastal slopes of the San Diego County mountains and Santa Ana Mountains. Winds are forecast to strengthen slightly through the morning, then weaken again this afternoon. Otherwise dry and warm today with highs 7-15 degrees above normal west of the mountains and around 3-5 degrees above normal elsewhere. High temperatures for inland coastal areas and the western valleys could reach 90 degrees in spots.

Offshore flow continues to weaken on Monday, then remains weak through at least Thursday. Weak upper level ridging remains in place through Tuesday, then the ridge amplifies across the Southwest on Wednesday ahead of a trough developing off the coast, both of which shift east on Thursday. This will maintain warm and dry weather for much of the week with widespread high temperatures 5-10 degrees above normal: mid to upper 80s for the coastal areas and valleys, low 60s to low 70s in the mountains, mid to upper 70s in the high desert, and mid to upper 80s in the low desert.

Global ensembles have trended slower with the onset of precipitation late in the week, with slight chances now beginning late Friday. Significant differences remain in the evolution of the upper level pattern as the jet tries to split. Around 47% of the ensemble members (as well as the deterministic EC and GFS) for a deep closed low in the southern stream and digs it south off the coast of CA and potentially into northern Mexico late Friday into Saturday. Models are notoriously poor at forecasting the track/timing of such systems, so if this pattern holds the precipitation forecast will likely change - potentially significantly - over the next few days. Around 31% of the members show a weaker open wave developing in the southern stream, which would be more progressive (precipitation starting and ending earlier with less accumulation). The remaining 22% does not produce any split flow with zonal winds across So Cal Friday and Saturday. Current NBM forecast favors the further south closed low scenario with higher precipitation probabilities over San Diego County on Saturday (20-30%), decreasing to the north (15-20%). NBM chances of moderate precipitation (48 hr total of at least 0.50") remains around 20% for the mountains westward. The only certain thing for Friday and Saturday is cooling with increasing cloud cover.

AVIATION

081030...SKC and VFR regionwide. E/NE winds strengthen and become more widespread once more after 17Z, primarily in San Diego County and in the Inland Empire downwind of the Banning Pass. Gusts 25-35 kts for coastal slopes/foothills and downwind of passes and corridors of gusts 15-25 kts into the valleys through this afternoon, before winds become isolated to the foothills again this evening.

MARINE

No hazardous marine conditions are expected through Thursday.

BEACHES

High tides will exceed 7 feet each morning through Tuesday, peaking today and Monday at 7.4-7.6 feet. A northwest swell at 2-3 feet with a period of 14-15 seconds will lead to surf of 3-6 feet with sets to along west-facing beaches today, with 3-4 foot waves more likely along south-facing beaches. This NW swell will increase to 3-4 feet Monday, which will increase surf to 4-7 feet for west-facing beaches through Tuesday. Surf on the San Diego Co coast will lead to hazardous swimming conditions and very strong rip currents through Tuesday night.

The combination of high tides and elevated surf will generate minor coastal flooding, with chances for moderate coastal flooding along west-facing beaches where surf will be higher. A Coastal Flood Advisory remains in effect through noon Tuesday for both the San Diego and Orange County coastlines. A Beach Hazards Statement is in effect as well for San Diego County through late Tuesday fro elevated surf and strong rip currents.

Reminder, tides mentioned have been corrected to reflect the current trends in actual tide observations.

SKYWARN

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

SGX WATCHES/WARNINGS/ADVISORIES

CA...Coastal Flood Advisory until noon PST Tuesday for Orange County Coastal Areas-San Diego County Coastal Areas.

Beach Hazards Statement through Tuesday evening for San Diego County Coastal Areas.

PZ...None.