textproduct: San Diego

SYNOPSIS

Widespread moderate with areas of major HeatRisk will continue through Friday. HeatRisk will decrease for the weekend, with minor cooling. Even with the cooling, temperatures will remain above average into next week. Patchy marine layer low clouds and fog will be present at times, most likely to impact the coastal waters and immediate coast.

DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE

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

Multiple daily and monthly high and low temperature records were broken yesterday with more expected to be broken today and Friday. The latest record report is headlined on our weather.gov/sandiego homepage. A climate section can be found below listing locations that are currently forecast to tie or break their monthly records. 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 over the California/Arizona border today with 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 inland 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 60 percent for Indio, 20 percent for Palm Springs, and 10 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 afternoon into Monday morning. Ridging aloft looks to rebuild Monday and strengthen into the middle of the week. This ridge isn't expected to be as strong as the one over Southern California this week, but it will be enough to maintain above average temperatures through next Thursday. Widespread minor with areas of moderate HeatRisk will be present in the valleys and low desert for much of next week.

With the ridge axis shifted further east today, weak onshore flow has returned to coastal areas. The weak onshore flow was enough to allow patchy dense fog along the immediate coast this morning. Areas of patchy dense fog over the water and at the coast is possible each morning through Saturday. With the aforementioned passing weak low pressure onshore flow will briefly increase, making chances of dense fog less likely for Sunday morning. Low cloud and fog coverage on Sunday morning may reach into the western valleys. Weak offshore flow early next week may keep low clouds and fog patchy and more confined to the immediate coast again.

AVIATION

191800Z...Low clouds and fog have moved offshore with VFR conditions expected through 03Z Friday. low clouds and patchy fog will make its return along the coast beginning after 03Z Friday near KSAN, touching into other coastal TAF sites after 06Z-07Z. Highest impacts are expected at KSAN at this time with clearing 16Z-17Z. Everywhere else, VFR conditions expected through the TAF period.

MARINE

Still some patchy fog out over the local waters this morning, but is making a slow retreat to the outer waters. Expect patchy fog development in the late afternoon to early evening hours but not expecting it to be dense at this time. Otherwise, no hazardous marine conditions are expected through Tuesday.

CLIMATE

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

Today: FORECAST HIGH RECORD YEAR AVG +/- RAMONA 95 92 IN 1997 68 28 Monthly Record: 94 BIG BEAR LAKE 82 70 IN 1997 52 28 Monthly Record: 80 IDYLLWILD 91 77 IN 1997 60 27 Monthly Record: 82 PALOMAR MOUNTAIN 88 76 IN 2007 57 28 Monthly Record: 82 LAKE CUYAMACA 88 79 IN 1956 56 30 Monthly Record: 82 CAMPO 97 87 IN 1997 69 26 Monthly Record: 92 PALM SPRINGS 107 97 IN 1997 80 29 Monthly Record: 104 INDIO 108 98 IN 1997 81 28 Monthly Record: 104 THERMAL 108 101 IN 1997 82 29 Monthly Record: 103 BORREGO 107 95 IN 2017 80 24 Monthly Record: 101

Friday:

FORECAST HIGH RECORD YEAR AVG +/- RAMONA 96 92 IN 1997 68 28 Monthly Record: 94 BIG BEAR LAKE 80 72 IN 2004 52 29 Monthly Record: 80 IDYLLWILD 88 79 IN 2004 60 27 Monthly Record: 82 PALOMAR MOUNTAIN 87 76 IN 1972 57 29 Monthly Record: 82 LAKE CUYAMACA 88 75 IN 2004 56 32 Monthly Record: 82 CAMPO 97 92 IN 1997 69 27 Monthly Record: 92 PALM SPRINGS 109 98 IN 2004 80 31 Monthly Record: 104 INDIO 109 100 IN 2004 81 31 Monthly Record: 104 THERMAL 110 101 IN 2004 82 32 Monthly Record: 103 BORREGO 108 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: Friday:

FORECAST LOW RECORD YEAR

RIVERSIDE 68 58 IN 1995 Monthly Record: 66 LAKE ELSINORE 63 57 IN 1940 Monthly Record: 61 ALPINE 71 58 IN 2001 Monthly Record: 63 IDYLLWILD 64 45 IN 2017 Monthly Record: 50 LAKE CUYAMACA 65 51 IN 2017 Monthly Record: 55 PALM SPRINGS 76 69 IN 1932 Monthly Record: 70 THERMAL 71 68 IN 1989 Monthly Record: 69 BORREGO 72 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.