High pressure aloft will build over the Four Corners region and remain in place through most of next week, leading to steadily increasing temperatures. By Saturday or Sunday, this could result in dangerous and significant heat risks across the interior, lasting for several days. Monsoonal moisture will bring a slight chance of showers and thunderstorms.
Today, a southeast flow aloft and rising high pressure will develop, continuing into Saturday as a large, hot upper high moves westward from Texas.
A significant monsoonal push is expected to arrive this evening. Mid and high clouds, along with convection, are likely to disrupt most of the marine layer clouds south of Point Conception. Although there is a better chance of low clouds across the Central Coast, these too could be disrupted. There is a small chance of thunderstorms, which could produce dry lightning over higher elevations due to their higher atmospheric base. Dry lightning can cause fires, leading to a fire weather watch being issued.
By Saturday, the upper-level flow will turn to the south, making convection less favorable. However, some afternoon convection can't be ruled out. High pressure will continue to build, with temperatures across the interior expected to rise by another 1 to 3 degrees. This will bring maximum temperatures up to 5 to 10 degrees above normal, likely resulting in heat advisories for several inland locations, with a chance of warnings being issued.
The upper high will remain near the Four Corners area through the extended period, with moderate onshore flow keeping coastal areas relatively cool. The marine layer will be compressed to about 1000 feet, preventing low clouds from reaching the interior and some deeper coastal valleys.
Interior temperatures will consistently remain 5 to 10 degrees above normal, ranging from 100 to 105 degrees, with some areas exceeding 105 degrees. Heat advisories are expected to be issued for many inland areas for all four days of this prolonged heat event.
Fortunately, the absence of offshore flow means coastal regions will avoid the heat, with maximum temperatures mostly in the 70s.
