textproduct: San Diego

SYNOPSIS

Well above average conditions will continue through the end of the week. Some cooling is expected through the weekend into early next week, but temperatures will remain above average. Marine layer low clouds and fog will be largely absent from the coast this week, potentially returning by late this weekend.

DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE

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

Evening update... A weak coastal eddy is developing this evening, bringing a fog bank to the far southern San Diego County coast. Visibility may be reduced to a few hundred feet at times at the beaches generally from La Jolla southward this evening. The land breeze should push this fog back out to sea tonight. Forecast was updated to reflect this brief period of dense fog.

Otherwise the big story remains to be the heat. Numerous daily record high temperatures were broken again today, along with a few monthly record highs including Thermal and Indio with a high of 107 degrees. The complete Record Event Report is headlined on our website. Expect record breaking heat to continue through Friday, especially for the mountains and deserts, as the upper level high strengthens and shifts eastward. With at least a weak sea breeze developing each afternoon, temperatures will moderate a bit near the coast but still be well above normal - just not in monthly record territory. See the Climate section below for more details on forecasted temperatures and records.

Previous discussion... Widespread moderate to locally major HeatRisk is expected through Friday for most locations and Saturday in the low desert. Reduce outdoor activities if possible between 10 AM and 5 PM, seek shade, and stay hydrated.

The high pressure aloft will peak in strength Friday with high temperatures 20 to 30 degrees above average for this time of year. Overnight lows will also be elevated, which will limit overnight relief from the heat for most locations. Through Friday Widespread temperatures in the 90s to low 100s expected for the inland valleys, with highs in the mid-80s to low 90s for coastal areas away from the immediate coast and the lower elevations of the mountains. In the low deserts, highs will likely exceed 105 degrees in most locations through Saturday. Chances for exceeding 110 degrees on Friday are 70 percent for Indio, 30 percent for Palm Springs, and 20 percent for Borrego Springs. In the High Desert, temperatures will be in the mid- 90s.

Weakening high pressure aloft and strengthening onshore flow will bring 4 to 8 degrees of cooling Saturday. That will be most noticeable for locations west of the mountains, but even the deserts will cool 3 to 5 degrees. A weak low pressure system aloft will move east through Southern California into the Great Basin sometime Sunday or Monday. that will bring an uptick in westerly winds Saturday, which have the potential to turn weakly offshore by Sunday or Monday. Weak ridging aloft will return sometime next Tuesday or Wednesday, maintaining above average temperatures. Low clouds will remain absent from the coast through the work week. Patchy low clouds may return with the return of onshore flow over the weekend.

AVIATION

190000Z...Mostly clear skies and VFR conditions through Thursday afternoon. Patchy fog over coastal waters tonight into Thursday, but unlikely to impact coastal airports.

MARINE

No hazardous marine conditions are expected through Sunday.

CLIMATE

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

Thursday: FORECAST HIGH RECORD YEAR AVG +/- RAMONA 96 92 IN 1997 68 28 Monthly Record: 94 BIG BEAR LAKE 81 70 IN 1997 52 28 Monthly Record: 80 IDYLLWILD 88 77 IN 1997 60 27 Monthly Record: 87 PALOMAR MOUNTAIN 86 76 IN 2007 57 28 Monthly Record: 82 LAKE CUYAMACA 88 79 IN 1956 56 30 Monthly Record: 84 CAMPO 97 87 IN 1997 69 26 Monthly Record: 96 PALM SPRINGS 108 97 IN 1997 80 29 Monthly Record: 105 INDIO 108 98 IN 1997 81 28 Monthly Record: 107 THERMAL 108 101 IN 1997 82 29 Monthly Record: 107 BORREGO 106 95 IN 2017 80 24 Monthly Record: 104

Friday:

FORECAST HIGH RECORD YEAR AVG +/- RAMONA 97 92 IN 1997 68 28 Monthly Record: 94 BIG BEAR LAKE 81 72 IN 2004 52 29 Monthly Record: 80 IDYLLWILD 88 79 IN 2004 60 27 Monthly Record: 87 PALOMAR MOUNTAIN 87 76 IN 1972 57 29 Monthly Record: 82 LAKE CUYAMACA 88 75 IN 2004 56 32 Monthly Record: 84 CAMPO 97 92 IN 1997 69 27 Monthly Record: 96 PALM SPRINGS 108 98 IN 2004 80 31 Monthly Record: 105 INDIO 109 100 IN 2004 81 31 Monthly Record: 107 THERMAL 111 101 IN 2004 82 32 Monthly Record: 107 BORREGO 107 97 IN 1997 80 26 Monthly Record: 104

Here are a list of locations currently forecast to break/tie monthly highest low temperature records Wednesday through Friday: 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 BORREGO 70 64 IN 2013 Monthly Record: 70

Friday:

FORECAST LOW RECORD YEAR

RIVERSIDE 68 58 IN 1995 Monthly Record: 66 LAKE ELSINORE 64 57 IN 1940 Monthly Record: 61 ALPINE 72 58 IN 2001 Monthly Record: 63 IDYLLWILD 67 45 IN 2017 Monthly Record: 50 LAKE CUYAMACA 66 51 IN 2017 Monthly Record: 55 PALM SPRINGS 75 69 IN 1932 Monthly Record: 75 THERMAL 70 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...Heat Advisory until 8 PM PDT Friday for Orange County Coastal Areas-Orange County Inland Areas-Riverside County Mountains- San Bernardino County Mountains-San Bernardino and Riverside County Valleys-The Inland Empire-San Diego County Coastal Areas-San Diego County Mountains-San Diego County Valleys-Santa Ana Mountains and Foothills.

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

PZ...None.