Here I am, sitting in my apartment outside Reno where the temperature is in the 70s and my wife is already listening to Christmas music, but in the Los Angeles and San Diego areas record-setting heat is sending the region above 100 in many places. Yesterday, downtown Los Angeles marked down a high of 102º. Excessive Heat Warnings continue for Los Angeles and San Diego as temperatures are expected to climb to near or above 100 again along I-5 and I-15. These highs are combining with low humidities and Santa Ana winds to create dangerous fire conditions. In fact, I-210 in Rancho Cucamonga was closed earlier due to a brush fire.
Record highs were set in several places yesterday, including Los Angeles and Oxnard. Temperatures today were already above 106 in some places at 2pm. Temperatures will be warmest west of the mountains but will be slightly subdued within a few miles of the ocean. The HRRR model has Los Angeles out for 105 today.
As mentioned earlier, this heat is combining with a stiff breeze and low humidities to create dangerous fire conditions. Dew points are down in the 20s for most areas, placing the relative humidity below 10%. Wind speeds are expected to exceed 20mph.
The barbs on the above weather model are wind speeds and point toward where the wind is coming from. The forecast is calling for winds out of the east for Southern California west of the mountains, providing the offshore flow that drives the humidity away. Today, the wind is essentially coming south out of Utah, across southern Nevada and then kicks more westward as it approaches I-5.
Cooler temperatures are expected to start tomorrow, with highs in the 90s. By Friday, the area west of the mountains will largely be into the 80s. Winds will switch to out of the west Thursday afternoon and evening. Dew points will rise tomorrow.