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.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
, NEW AVIATION DISCUSSION BELOW,
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.
190600z, Low CIGs/FG are currently moving up along the southern coast of San Diego County, which will intermittently move over KSAN through the morning with reduced visibilities down to 1/2 SM and CIGs typically around 100-300 ft AGL, especially through 07Z. Otherwise, mostly clear skies and VFR conditions through Thursday evening elsewhere. Patchy fog over coastal waters tonight into Thursday morning.
No hazardous marine conditions are expected throughSunday.
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.
