textproduct: San Diego

SYNOPSIS

Warmer weather through Saturday with low clouds and patchy fog closer to the coast each morning. Tropical mid and high level moisture brings more clouds and cooler temperature, along with a slight chance of light showers for our southeastern regions by Sunday and Monday. Weak high pressure moves into the area by next Tuesday, returning to warmer and drier.

..UPDATED AVIATION DISCUSSION

Mid-level water vapor imagery shows a deep low over the PacNW and Hurricane Odalys strengthening to the southwest of Baja. Weak ridging remains over SoCal with drier air aloft, allowing temperatures to warm both today and tomorrow to around 5-8 degrees above normal. A trough off the backside of the larger low to the north will swing down late Saturday and attempt to capture some of the moisture associated with Hurricane Polo and Hurricane Odalys, increasing PWs above 1-1.5". This could lead to elevated overnight temperatures both Saturday and Sunday for coastal areas and moderate HeatRisk is expected for Saturday. By Sunday, heavier cloud cover and decreasing heights will help moderate temperatures a bit, which look to cool almost 10 degrees below Saturday's highs.

Right now, GFS guidance attempts to bring in drier air on the backside of the trough late weekend, which could shunt the moisture to the east as the trough moves across, severely limiting precipitation chances for Sunday night and Monday. The ECMWF remains the more wet model, indicating some light precipitation for SoCal. With such disagreement in global models even 48-72 hours out, confidence in rainfall amounts in this forecast package remain very low. For now, the aforementioned trough may bring about some light rain showers for at least the San Diego County Mountains, Riverside County Mountains and lower deserts (including Coachella Valley), about a 20-25% chance, although any accumulation isn't expected to be very high, likely 0.2" or less. Even if no accumulation occurs for our region, ample high clouds over nearly the entire region and mid-level moisture for the mountains and further east will likely lead to some uncomfortable humidity. Outside of the humidity and low precipitation chances, some other observable impacts associated with the tropical cyclones include coastal flooding and erosion, which is further discussed in the Beaches section below.

As the trough starts to propagate into Arizona on Monday, any lingering moisture will be pushed eastward as drier air filters in and ridging begins to build to the west, with PWs falling sharply. Temperatures will begin to warm, and weak offshore flow looks to set up by mid to late week which could push temperatures even higher with dry downsloping winds. Since models remain misaligned even in the short term, trying to dictate the upper level pattern after Wednesday is extremely difficult. Ultimately, how the trough moves out and how quickly ridging build behind will play a large impact in the general trend for the end of next week.

AVIATION

251900Z...Coast/Valleys...VFR conditions expected through this evening. Patchy low clouds to redevelop after 05Z Sat, based at around 600-900 feet MSL. Clouds may become more uniform and push up to 10-15 miles inland for a period from 10-15z. Minor vis reductions (1-5SM) expected for higher coastal terrain and western valleys. Clouds scatter out around 15-16z.

Mountains/Deserts...Cumulus and isolated CBs are currently developing over mountains and may lead to an isolated SHRA/TSRA 20- 00Z.

Regionwide...Increasing SCT-BKN clouds around 20 kft after 00Z.

MARINE

No hazardous marine conditions are expected through Tuesday.

BEACHES

Southwesterly swell (3-4 ft at 13 seconds from ~210 degrees) from Hurricane Odalys increases today, bringing surf of 3-5 feet with sets up to 6 feet, highest along south and southwest facing beaches. This swell from Odalys is expected to persist through this weekend. Tides are already observed over 6 feet and are expected to gradually increase into this weekend, therefore a Beach Hazard Statement is now in effect and will continue through next Wednesday afternoon. Minor tidal overflow and minor coastal erosion are the primary impacts.

The swell from Hurricane Polo (3 ft at 14 seconds from ~170 degrees) increases on Monday. Given this direction, most of San Diego County beaches will be largely sheltered from this swell, but Orange County beaches especially in north county should be impacted. Meanwhile, a northwesterly swell (3-4 ft at 8 seconds from ~290 degrees) arrives late Sunday and early Monday. Between these two swells, surf of 3-5 feet with sets to 6 feet looks probable along south/southwest facing beaches with surf 2-4 feet along west-facing beaches through Tuesday. Tides peak Monday-Wednesday mornings near 7.0 ft. Higher tides and elevated surf will combine to generate a risk for minor- moderate coastal flooding during the late morning/early afternoon high tides, especially along south/southwest facing beaches. An upgrade to a Coastal Flood Advisory appears likely for the Monday- Tuesday time frame.

Please note - listed tide predictions have been adjusted to reflect actual measured tide observations.

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 Wednesday afternoon for Orange County Coastal Areas-San Diego County Coastal Areas.

PZ...None.