Excessive heat warning through tonight, some reprieve this weekend

August 16, 2019 – Excessive Heat Warning continues today for Valley and foothill locations. Cooler over the weekend with below normal temperatures by Sunday.

Warming slowly through next week to a little above normal. No precipitation expected interior NorCal through the extended period.

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Discussion

Mild temperatures this morning with most areas running just a little higher than yesterday morning at this time. Models are trending today’s high temperatures down just slightly from Thursday as a weak trough drops through the Pacific Northwest but highs will still be about 10 degrees above normal and a excessive heat warning will remain in place for today.

Weak upper troughing sags over NorCal on Saturday bringing a little more cooling although highs on Saturday will still run a few to several degrees above normal. No precipitation is expected with this week system or even much in the way of cloud cover. The exception to this might be the delta region where a much increased delta breeze may bring some morning coastal stratus. The delta and near delta areas will also be the locations of greatest cooling Saturday.

A more significant cooling should occur on Sunday as a more significant trough digs into the eastern Pacific. Stable southwest flow aloft will keep fair skies over the north state as high temperatures drop to a few degrees below normal. High pressure starts to rebuild over the west coast on Monday bringing the start of the next warm up and a decreasing delta flow. Daytime highs warm back up to close to normal Monday to start off a warming trend going into next week.

Extended Discussion (Tuesday through Friday)

The residual trough across the region will be nearly non-existent by Tuesday as a downstream upper ridge gradually strengthens over the Four Corners region. As has commonly occurred this summer, the mentioned ridge will expand both north and west allowing heights to rise over the state.

The response to this setup will be an increase in temperatures carrying Valley highs into the upper 90s by mid-week, locally into the lower 100s across the northern Sacramento Valley.

By later in the work week, ensemble means show a low amplitude trough approaching the West Coast which may nudge the ridge out of the region. Overall, expect the period to be comprised of slightly above average temperatures (roughly 4 to 7 degrees at times) with some overnight relief given weak Delta Breeze influences.