textproduct: San Diego

SYNOPSIS

Hot conditions with record breaking temperatures this week. Weak offshore flow today will gradually transition to onshore flow by Thursday. Some cooling is expected through the weekend into early next week. Even with the cooling, high temperatures will remain above average. Marine layer low clouds and fog will be largely absent from the coast this week, potentially returning for this weekend.

DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE

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

Weak offshore flow continues this evening and several coastal and inland locations are still reporting temperatures in the 90-100 degree range. The offshore pressure gradients are being supported by easterly flow aloft, mainly due to the position of the upper level high centered to our north. This has allowed temperatures to reach the 90s as far west as San Clemente Island! Many daily maximum temperature records were broken or tied today. See our Record Event Report. Widespread moderate to locally major HeatRisk is expected each day this week. Reduce outdoor activities if possible between 10 AM and 5 PM, seek shade, and stay hydrated.

Places along the immediate coast will see some relief from the heat from Wednesday onward, as weak onshore flow returns. That won't be the case for inland locations where marine air is unlikely to reach, with an addition 3 to 5 degrees of warming on Wednesday and even further warming for Thursday and Friday. The high pressure aloft will peak in strength on Thursday or Friday with high temperatures 20 to 30 degrees above average for this time of year. Daily and monthly temperature records are expected to be broken or tied for locations like Ramona, Big Bear Lake, Idyllwild, Palm Springs, and Borrego Springs. More information on monthly temperature records can be found in the climate section below. Overnight lows will also be elevated, which will limit overnight relief from the heat for most locations...at least for the next 2-3 days.

Weakening high pressure aloft and strengthening onshore flow will bring 5 to 7 degrees of cooling to places west of the mountains Saturday, with cooling spreading to the mountains and deserts Sunday and Monday. Weak ridging aloft will maintain highs 10 to 20 degrees above average across the area through at least next Tuesday. Much of this week will see an absence of marine layer low clouds and fog, with the potential for clouds and fog to return to coastal areas late in the weekend or early next week.

AVIATION

180400Z...VFR conditions expected through the TAF period. Patchy low clouds will develop along the coast beginning near KSAN after 05Z and stretching north near KCRQ after 06Z. Not expecting any impacts to cigs or vis at coastal airports.

MARINE

No hazardous marine conditions are expected through Saturday.

BEACHES

A long period (17-19 second) south-southwesterly swell (190-200 degrees) to 3-5 feet will continue today, bringing occasional surf sets up to 6 feet on south-facing beaches, before decreasing Wednesday evening. Locally hazardous swimming conditions are expected. A Beach Hazards Statement contains more details.

CLIMATE

Here are a list of locations currently forecast to break/tie monthly high temperature records Wednesday through Friday:

Wednesday: HIGH RECORD YEAR AVG +/- RAMONA 94 89 IN 1997 68 26 Monthly Record: 94 IDYLLWILD 85 75 IN 2004 60 25 Monthly Record: 82 PALOMAR MOUNTAIN 83 74 IN 2004 57 25 Monthly Record: 82 LAKE CUYAMACA 85 76 IN 2007 56 30 Monthly Record: 82 CAMPO 94 89 IN 2004 68 26 Monthly Record: 92 PALM SPRINGS 106 95 IN 1990 79 28 Monthly Record: 104 INDIO 105 99 IN 2007 81 26 Monthly Record: 104 THERMAL 106 97 IN 1997 82 27 Monthly Record: 103 BORREGO 103 97 IN 1972 80 24 Monthly Record: 101

Thursday: FORECAST HIGH RECORD YEAR AVG +/- RAMONA 97 92 IN 1997 68 28 Monthly Record: 94 BIG BEAR LAKE 80 70 IN 1997 52 28 Monthly Record: 80 IDYLLWILD 87 77 IN 1997 60 27 Monthly Record: 82 PALOMAR MOUNTAIN 85 76 IN 2007 57 28 Monthly Record: 82 LAKE CUYAMACA 87 79 IN 1956 56 30 Monthly Record: 82 CAMPO 95 87 IN 1997 69 26 Monthly Record: 92 PALM SPRINGS 107 97 IN 1997 80 29 Monthly Record: 104 INDIO 106 98 IN 1997 81 28 Monthly Record: 104 THERMAL 108 101 IN 1997 82 29 Monthly Record: 103 BORREGO 105 95 IN 2017 80 24 Monthly Record: 101

Friday:

FORECAST HIGH RECORD YEAR AVG +/- RAMONA 95 92 IN 1997 68 28 Monthly Record: 94 BIG BEAR LAKE 81 72 IN 2004 52 29 Monthly Record: 80 IDYLLWILD 87 79 IN 2004 60 27 Monthly Record: 82 PALOMAR MOUNTAIN 85 76 IN 1972 57 29 Monthly Record: 82 LAKE CUYAMACA 87 75 IN 2004 56 32 Monthly Record: 82 CAMPO 96 92 IN 1997 69 27 Monthly Record: 92 PALM SPRINGS 108 98 IN 2004 80 31 Monthly Record: 104 INDIO 108 100 IN 2004 81 31 Monthly Record: 104 THERMAL 108 101 IN 2004 82 32 Monthly Record: 103 BORREGO 106 97 IN 1997 80 26 Monthly Record: 101

Here are a list of locations currently forecast to break/tie monthly highest low temperature records Wednesday through Friday:

Wednesday:

FORECAST LOW RECORD YEAR

RIVERSIDE 67 57 IN 1995 Monthly Record: 66 LAKE ELSINORE 63 55 IN 2015 Monthly Record: 61 ESCONDIDO 63 59 IN 2015 Monthly Record: 63 ALPINE 69 58 IN 1978 Monthly Record: 63 LAKE CUYAMACA 62 51 IN 2015 Monthly Record: 55 PALM SPRINGS 73 68 IN 2004 Monthly Record: 70 Thursday:

FORECAST LOW RECORD YEAR

RIVERSIDE 67 57 IN 1995 Monthly Record: 66 LAKE ELSINORE 62 56 IN 1986 Monthly Record: 61 ALPINE 69 55 IN 1990 Monthly Record: 63 IDYLLWILD 64 43 IN 2017 Monthly Record: 50 LAKE CUYAMACA 64 53 IN 2017 Monthly Record: 55 CAMPO 58 51 IN 1951 Monthly Record: 58 PALM SPRINGS 74 64 IN 2017 Monthly Record: 70 BORREGO 70 64 IN 2013 Monthly Record: 70

Friday:

FORECAST LOW RECORD YEAR

RIVERSIDE 67 58 IN 1995 Monthly Record: 66 LAKE ELSINORE 64 57 IN 1940 Monthly Record: 61 ALPINE 70 58 IN 2001 Monthly Record: 63 IDYLLWILD 66 45 IN 2017 Monthly Record: 50 LAKE CUYAMACA 64 51 IN 2017 Monthly Record: 55 PALM SPRINGS 75 69 IN 1932 Monthly Record: 70 THERMAL 69 68 IN 1989 Monthly Record: 69 BORREGO 71 65 IN 2017 Monthly Record: 70

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 evening for Orange County Coastal Areas-San Diego County Coastal Areas.

Heat Advisory until 8 PM PDT Friday 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.

Heat Advisory from 10 AM Wednesday to 8 PM PDT Friday for Riverside County Mountains-San Bernardino County Mountains- San Diego County Mountains.

Extreme Heat Warning from 10 AM Wednesday to 8 PM PDT Saturday for Coachella Valley-San Diego County Deserts-San Gorgonio Pass near Banning.

PZ...None.