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Hot weather forecast is already prompting advisories

Posted at 4:21 PM, Sep 01, 2020

A huge ridge of high pressure will build over the Western United States between Thursday and Monday of next week. While ridges of high pressure are nothing new for California the strength of this one certainly is.

The ridge strength is the kind we see fewer than once in ten years, in fact it could end up being one of the strongest we've seen on this part of the calendar.

Does this mean record heat? Yes, very likely. the 100-115 range is certainly on deck for the interior valleys and even coastal valleys will see temps in the 90s if not some scattered 100 degree readings between Friday and Monday.

There are a number of issue to consider with this forecast. First, of course, the heat. An excessive heat watch has been issued for much of California. This means temperatures much above average are likely and precautions are necessary: avoiding peak heat of the day, hydration, and awareness of the health of others and animals.

Additionally, heat like this is a serious fire concern. This ridge will drive significant offshore flow as early as Friday. This will mean the air will be warm AND dry. Fuels react much differently under these circumstances than with lower temperatures and more significant relative humidity rebound in the evenings and overnights.

The component of this being a holiday weekend will mean that many more people will likely be out and about. This can increase fire starts.

It currently appears that beaches will offer some relief from the heat away from the beaches. Models are indicating the potential for some afternoon onshore winds which should mean beaches escape the extreme component of the forecast. That said if the ridge is intense winds could remain offshore and forecasts could be revised upwards.

Temperatures look to back off a little Tuesday and continues to moderate thru the rest of the week.

All that being said, the short term forecast is still mild enough on Wednesday with more extensive marine layer near the coast. Gradually less marine influence on Thursday and by Friday the offshore flow begins and the broader warm-up begins.