textproduct: San Diego

SYNOPSIS

The long duration heatwave is past its halfway point, but extreme heat will persist through tomorrow for the coasts and valleys, and through Friday for the lower deserts. Cooling temperatures are expected for the weekend onward. A low pressure system will combine with tropical moisture, bringing showers Sunday into Tuesday, with the greatest chances of rain on Sunday into Monday.

SHORT TERM (Today through Saturday)

The long-duration heatwave will continue for the coast and valleys through Thursday, and through Friday for the lower deserts. Inland areas will warm a few degrees today, while the coast into the western San Diego County valleys cools a few degrees. There will be High to locally Extreme HeatRisk for the beaches and far inland valleys today, dropping to Moderate to locally Major HeatRisk tomorrow. There will be areas of Major to locally Extreme HeatRisk for the lower deserts today through Friday. High temperatures will range from the upper 70s to mid 80s near the coast to the 90s for the Inland Empire with 102 to 106 for the lower deserts for the duration of the heat. By Saturday, cooling will be very noticeable and only minor to locally moderate HeatRisk is expected.

Low clouds and locally dense fog over the coastal waters this evening will spread inland along the coast for late tonight into Thursday morning. Followed by a little farther inland spread of the low clouds into coastal areas for late Thursday night into Friday morning as the marine layer slowly deepens.

LONG TERM (Sunday through Wednesday)

The cooling trend will continue into early next week, with high temperatures falling to as much as 10 to 15 degrees below average for the mountains, deserts, and inland valleys. High temperatures Monday through Wednesday will be mostly in the upper 60s to low 70s for the coast and valleys, with the lower deserts in the lower to mid 80s. This will make for temperatures 20-30 degrees cooler than observed just a few days earlier during the heatwave.

A low pressure system will absorb the moisture from what is left of former Hurricane Rachel, then move northeastward into extreme southern California and northern Baja. This will bring showers chances for Sunday through Tuesday with the greatest chances of rain Sunday into Monday. Rain totals for the whole event may as high as around 0.50 to 2.00 inches (highest in the mountains) for portions of the forecast area. There could be a few inches of snowfall on the very highest mountain peaks above 9000 feet for Monday night and Tuesday as snow levels may briefly fall as low as 8000 feet.

Onshore winds will strengthen for Sunday and Monday with southwest to west winds for Sunday afternoon through Monday morning gusting to 20 to 30 mph for the coastal waters to the valleys and to 35 to 45 mph for the mountains and deserts with gusts to 55 to 65 mph for the northern Coachella Valley below the San Gorgonio Pass. There is the potential for strong wind from the coastal waters to the deserts Sunday into Monday.

Please continue to monitor the forecast for the dynamic impacts due to remnants of Rachel.

AVIATION

080530Z...Coast...Patchy low clouds with bases below 400-500 feet MSL will gradually become more widespread after 09Z. There is a 50- 60% chance of CIGS below 300 ft MSL with vis 1/2 SM or less in FG at KSAN and KCRQ 11-15Z, and around a 40% chance at KSNA during that time frame. Low clouds and fog based around 800 feet MSL to redevelop after 07Z Friday.

Otherwise...mostly clear through Thursday except for shallow cumulus over mountains 19-01Z.

MARINE

No hazardous marine conditions are expected through Saturday. Southwest to west winds strengthen Sunday and continue into Monday, potentially creating conditions hazardous to small craft.

BEACHES

Surf of 3-5 feet with sets to 6 feet is expected on south and southwest facing beaches through Friday. Elevated surf and strong rip and longshore currents will create hazardous swimming conditions. This elevated surf will combine with high tides during the mornings and evenings to generate local coastal flooding and beach erosion. Another south swell and continued morning high tides near 7 feet will maintain a threat of coastal flooding and beach erosion into Tuesday. The Beach Hazards Statement and Coastal Flood Advisory contain the details.

SKYWARN

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

SGX WATCHES/WARNINGS/ADVISORIES

CA...Extreme Heat Warning until 8 PM PDT Thursday for Orange County Coastal Areas-Orange County Inland Areas-San Bernardino and Riverside County Valleys-The Inland Empire-San Diego County Coastal Areas-San Diego County Valleys-Santa Ana Mountains and Foothills.

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

Coastal Flood Advisory until 2 PM PDT Tuesday for Orange County Coastal Areas-San Diego County Coastal Areas.

Extreme Heat Warning until 8 PM PDT Friday for Coachella Valley- San Diego County Deserts-San Gorgonio Pass near Banning.

PZ...None.