textproduct: San Diego

SYNOPSIS

Near to slightly above average temperatures will only last through Wednesday before another heatwave begins. High pressure to the east is expected to strengthen and move westward late this week, bringing a return of moderate to major HeatRisk for Thursday onward into early next week. Temperatures peak Saturday and Sunday with some record highs expected in the mountains and deserts along with locally extreme HeatRisk. The marine layer and associated morning clouds will become more shallow and confined to coastal areas by late this week.

DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE

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

The main story this week is the incoming heatwave beginning on Thursday. An upper ridge currently located to the east will strengthen and move westward through this weekend. There is strong agreement among models that 500 mb heights will peak somewhere around 597 to 600 dm on Saturday, setting the stage for the hottest temperatures of the year so far for inland areas. High temperatures ranging from a few to 8 degrees above normal on Thursday will combine with slightly above normal lows to create moderate to locally major HeatRisk for inland areas. By the weekend, both high and low temperatures increase to 5 to 12 degrees above normal. Peak temperatures this weekend will range from the 80s in coastal areas to 115 to 120 in the low deserts. 90s expected in the western valleys and mountains below 7000 feet, low 100s in eastern San Diego Valleys, and 100s to near 110 in the Inland Empire and High Desert. This will create moderate HeatRisk for coastal areas, moderate to major HeatRisk for inland valleys and mountains, and major to extreme HeatRisk in the deserts. Some daily record highs are expected to fall in the mountains and deserts this weekend.

As a consequence of the building upper ridge, the marine layer is expected to become more shallow and confined to coastal areas by late week. Minor visibility reductions will become possible for coastal areas each morning this weekend. Additionally, increasing inversion strength may allow for marine layer clouds to persist into the afternoon along the immediate coastline. This adds uncertainty to current high temperature forecasts. Current highs are expected to range 5 to 10 degrees above normal (generally low 80s) along the coastline this weekend. If clouds are present in the afternoons, highs will be closer to seasonal averages.

The ridge is expected to weaken early next week, bringing a slight cooling trend. However, high temperatures are generally expected to remain above average. Thus, moderate heatrisk will likely continue for inland valleys/mountains with major HeatRisk in the deserts. Model guidance diverges more significantly from mid-next week onward, though there is some indication that a more favorable monsoon pattern will re-emerge.

AVIATION

281800Z....Coast/Valleys...Locally BKN-OVC at some beaches into the afternoon, with clear conditions elsewhere. Low clouds push inland 03-07Z Wed, with bases 700-1200 ft MSL. Most likely coastal TAF site for cigs below 1000 ft MSL is KCRQ, with only 40-50 percent chance at KSAN and KSNA. VIS 3-5SM where stratus nears higher coastal terrain and in the western valleys. Low clouds will scatter out 16- 18Z Wed.

Mountains/Deserts...Mostly clear skies and VFR conditions expected into Wednesday.

MARINE

No hazardous marine weather is expected through Sunday.

BEACHES

A south swell from 200 degrees of 3-4 ft feet at 17 seconds will produce surf of 3-6 feet with sets to 7 feet into Wednesday. Strong rip currents are expected along with minor tidal overflow during the evening high tide.

Wednesday, a 4-5 ft swell from 160-180 degrees with a period of 13- 15 seconds associated with Hurricane Genevieve will arrive. Surf of 5-9 ft is expected on south facing beaches in Orange County with surf around 3-6 ft elsewhere. Surf will peak on Thursday and Friday, when the swell direction shifts to 180-190 degrees. Strong rip and longshore currents will create dangerous swimming conditions at most area beaches. In addition to the high surf, evening high tides will be above 6 ft this week. The combination of high tides and surf increases the risk of coastal flooding. The swell, period, and tides are expected to decrease over the weekend.

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.

Coastal Flood Advisory from 5 PM Wednesday to 3 AM PDT Saturday for Orange County Coastal Areas-San Diego County Coastal Areas.

High Surf Advisory from 5 PM Wednesday to 5 PM PDT Saturday for Orange County Coastal Areas-San Diego County Coastal Areas.

Heat Advisory from 10 AM Friday to 8 PM PDT Sunday for Orange County Coastal Areas-San Diego County Coastal Areas.

Extreme Heat Warning from 10 AM Thursday to 8 PM PDT Sunday for Apple and Lucerne Valleys-Coachella Valley-Riverside County Mountains-San Bernardino and Riverside County Valleys-The Inland Empire-San Diego County Deserts-San Diego County Mountains-San Gorgonio Pass near Banning.

Extreme Heat Warning from 10 AM Friday to 8 PM PDT Sunday for Orange County Inland Areas-San Diego County Valleys-Santa Ana Mountains and Foothills.

Heat Advisory from 10 AM Thursday to 8 PM PDT Sunday for San Bernardino County Mountains.

PZ...None.